diff --git a/a1_ln2_openmp/.DS_Store b/a1_ln2_openmp/.DS_Store
new file mode 100644
index 0000000..5008ddf
Binary files /dev/null and b/a1_ln2_openmp/.DS_Store differ
diff --git a/a1_ln2_openmp.cpp b/a1_ln2_openmp/a1_ln2_openmp.cpp
similarity index 100%
rename from a1_ln2_openmp.cpp
rename to a1_ln2_openmp/a1_ln2_openmp.cpp
diff --git a/ln2 b/a1_ln2_openmp/ln2
similarity index 100%
rename from ln2
rename to a1_ln2_openmp/ln2
diff --git a/makefile b/a1_ln2_openmp/makefile
similarity index 100%
rename from makefile
rename to a1_ln2_openmp/makefile
diff --git a/test.h b/a1_ln2_openmp/test.h
similarity index 100%
rename from test.h
rename to a1_ln2_openmp/test.h
diff --git a/a2_ln2_mpi/.DS_Store b/a2_ln2_mpi/.DS_Store
new file mode 100644
index 0000000..5008ddf
Binary files /dev/null and b/a2_ln2_mpi/.DS_Store differ
diff --git a/a2_ln2_mpi/a2_ln2_mpi.cpp b/a2_ln2_mpi/a2_ln2_mpi.cpp
new file mode 100644
index 0000000..29633f2
--- /dev/null
+++ b/a2_ln2_mpi/a2_ln2_mpi.cpp
@@ -0,0 +1,62 @@
+#include <iostream>
+#include <mpi.h>
+#include "test.h"
+
+void runningWithMPITest();
+void computeLn2Test();
+
+// ****************************************************
+// TODO: parallelize this function with MPI
+// ****************************************************
+
+double ln2(int numTerms) {
+  int rank, numProcs;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &numProcs);
+
+  int start = 1 + (numTerms / numProcs) * rank;
+  int end = (numTerms / numProcs) * (rank + 1);
+
+  double localSum = 0;
+  
+  for (int i = start; i < end + 1; ++i) {
+    int sign = 1;
+    if (i % 2 == 0) {
+      sign = -1;
+    }
+    localSum += sign / static_cast<double>(i);
+  }
+
+  double globalSum;
+  MPI_Allreduce(&localSum, &globalSum, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
+
+  return globalSum;
+}
+
+int main(int argc, char* argv[]) {
+  MPI_Init(&argc, &argv);
+  runningWithMPITest();
+  computeLn2Test();
+  MPI_Finalize();
+}
+
+// Do not change anything below this line!
+// You may use the tests below to verify that your
+// program works correctly.
+// ****************************************************
+
+// Verify that the program actually runs with MPI
+void runningWithMPITest() {
+  int numProc;
+  MPI_Comm_size(MPI_COMM_WORLD, &numProc);
+  check(numProc, 4);
+}
+
+// Verify correct functionality of ln2()
+void computeLn2Test() {
+  check(ln2(4), 0.5833333333333333);
+  check(ln2(8), 0.6345238095238095);
+  check(ln2(12), 0.6532106782106781);
+  check(ln2(100), 0.688172179310195);
+  check(ln2(1e6), 0.6931466805602525);
+}
diff --git a/a2_ln2_mpi/ln2 b/a2_ln2_mpi/ln2
new file mode 100644
index 0000000..e82b111
Binary files /dev/null and b/a2_ln2_mpi/ln2 differ
diff --git a/a2_ln2_mpi/makefile b/a2_ln2_mpi/makefile
new file mode 100644
index 0000000..0b82dc5
--- /dev/null
+++ b/a2_ln2_mpi/makefile
@@ -0,0 +1,5 @@
+all: a2_ln2_mpi.cpp
+	mpicxx a2_ln2_mpi.cpp -std=c++17 -o ln2
+
+run: all
+	mpirun -np 4 ./ln2
\ No newline at end of file
diff --git a/a2_ln2_mpi/test.h b/a2_ln2_mpi/test.h
new file mode 100644
index 0000000..232be71
--- /dev/null
+++ b/a2_ln2_mpi/test.h
@@ -0,0 +1,290 @@
+/** test.h, an extremly simple test framework.
+ * Version 1.4
+ * Copyright (C) 2022-2023 Tobias Kreilos, Offenburg University of Applied
+ * Sciences
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * The framework defines a function check(a,b) that can be called with
+ * parameters of different types. The function asserts
+ * that the two paramters are equal (within a certain, predefined range for
+ * floating point numbers) and prints the result of the comparison on the
+ * command line. Additionally a summary of all tests is printed at the end of
+ * the program.
+ * Additionally there is TEST macro, which you can place outside main to group
+ * tests together. Code in the macro is automatically executed at the beginning
+ * of the program.
+ * The file also defines a class InstanceCount, that can be used to
+ * count how many instances of an object are still alive at the end of a
+ * program. To use it, derive your class from InstanceCount<ClassName> and the
+ * message is automatically printed at the end of the program.
+ */
+
+#ifndef VERY_SIMPLE_TEST_H
+  #define VERY_SIMPLE_TEST_H
+
+  #include <cmath>
+  #include <iostream>
+  #include <sstream>
+  #include <atomic>
+
+  /** Simple macro to execute the code that follows the macro (without call from
+   * main)
+   *
+   * Define a class, that is directly instantiated
+   * and contains the test code in the constructor.
+   *
+   * Usage:
+   * TEST(MyTest)
+   * {
+   *    // test code
+   * }
+   */
+  #define TEST(name)              \
+    struct _TestClass##name {     \
+      _TestClass##name();         \
+    } _TestClass##name##Instance; \
+    _TestClass##name::_TestClass##name()
+
+// Use a namespace to hide implementation details
+namespace Test::Detail {
+/**
+ * Make it possible to print the underlying value of class enums with ostream
+ *
+ * The expression typename std::enable_if<std::is_enum<T>::value,
+ * std::ostream>::type decays to ostream if the type T is an enum. Otherwise,
+ * the function is not generated.
+ */
+template <typename T>
+std::ostream& operator<<(
+    typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream,
+    const T& e) {
+  return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
+/**
+ * Convert anything to a string.
+ */
+template <typename T>
+std::string toString(const T& t) {
+  std::ostringstream ss;
+  ss << t;
+  return "\"" + ss.str() + "\"";
+}
+
+/**
+ * Convert bools to string "true" or "false" instead of 0 and 1
+ */
+template <>
+inline std::string toString<bool>(const bool& b) {
+  return b ? "\"true\"" : "\"false\"";
+}
+
+/**
+ * Comparison function for different types
+ */
+template <typename T>
+bool isEqual(const T& t1, const T& t2) {
+  return t1 == t2;
+}
+
+/**
+ * Double values are equal if they differ no more than 1e-12
+ */
+template <>
+inline bool isEqual<double>(const double& expectedValue,
+                            const double& actualValue) {
+  const double epsilon = 1e-12;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * Float values are equal if they differ no more than 1e-6
+ */
+template <>
+inline bool isEqual<float>(const float& expectedValue,
+                           const float& actualValue) {
+  const double epsilon = 1e-6;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * This class realizes some basics of the test framework.
+ * Test summary is printed in the destructor.
+ * Apart from that, the class implements counting of total and failed tests,
+ * comparison of floating point numbers within sensible boundaries and prints
+ * the result of each test on the command line.
+ */
+class Test {
+ public:
+  /**
+   * Test class is a Singleton
+   */
+  static Test& instance() {
+    static Test test;
+    return test;
+  }
+
+  /**
+   * the main entry point for tests. Test two values for equality and output the
+   * result.
+   */
+  template <typename T>
+  bool check(const T& expectedValue, const T& actualValue) {
+    bool testResult = isEqual(expectedValue, actualValue);
+    if (testResult == true) {
+      registerPassingTest();
+  #pragma omp critical
+      std::cout << "Test successful! Expected value == actual value (="
+                << toString(expectedValue) << ")" << std::endl;
+    } else {
+      registerFailingTest();
+  #pragma omp critical
+      std::cout << "Error in test: expected value " << toString(expectedValue)
+                << ", but actual value was " << toString(actualValue)
+                << std::endl;
+    }
+
+    return testResult;
+  }
+
+ private:
+  /**
+   * On destruction, print a summary of all tests.
+   */
+  ~Test() {
+    std::cout << "\n--------------------------------------" << std::endl;
+    std::cout << "Test summary:" << std::endl;
+    std::cout << "Executed tests: " << numTests_ << std::endl;
+    std::cout << "Failed tests: " << numFailedTests_ << std::endl;
+  }
+
+  void registerPassingTest() { numTests_++; }
+
+  void registerFailingTest() {
+    numTests_++;
+    numFailedTests_++;
+  }
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numTests_ = 0;
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numFailedTests_ = 0;
+};
+
+template <typename T>
+class InstanceCounterHelper {
+ public:
+  ~InstanceCounterHelper() {
+    std::cout << "The remaining number of objects of type " << typeid(T).name()
+              << " at the end of the program is " << count;
+    if (count > 0)
+      std::cout << " (NOT zero!)";
+    std::cout << "\nThe total number of objects created was " << total
+              << std::endl;
+  }
+
+  void increment() {
+    count++;
+    total++;
+  }
+
+  void decrement() { count--; }
+
+ private:
+  std::atomic<int> count = 0;
+  std::atomic<int> total = 0;
+};
+
+}  // namespace Test::Detail
+
+/**
+ * Count the instances of a class T.
+ * Result gets printed automatically at the end of the program.
+ * To use it, inherit T from InstanceCounter<T>, e.g.
+ * class MyClass : InstanceCounter<MyClass>
+ */
+template <typename T>
+class InstanceCounter {
+ public:
+  InstanceCounter() { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&) { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&&) { counter().increment(); }
+
+  virtual ~InstanceCounter() { counter().decrement(); }
+
+  Test::Detail::InstanceCounterHelper<T>& counter() {
+    static Test::Detail::InstanceCounterHelper<T> c;
+    return c;
+  }
+};
+
+/**
+ * Check if the expected value is equal to the actual value.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+template <typename T1, typename T2>
+void check(const T1& actualValue, const T2& expectedValue) {
+  const T1& expectedValueCasted{
+      expectedValue};  // allows conversion in general, but avoids narrowing
+                       // conversion
+  Test::Detail::Test::instance().check(expectedValueCasted, actualValue);
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const int& actualValue, const double& expectedValue) {
+  Test::Detail::Test::instance().check(expectedValue,
+                                       static_cast<double>(actualValue));
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const double& actualValue, const int& expectedValue) {
+  Test::Detail::Test::instance().check(static_cast<double>(expectedValue),
+                                       actualValue);
+}
+
+/**
+ * Check if the entered value is true.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+inline void check(bool a) {
+  Test::Detail::Test::instance().check(true, a);
+}
+
+#endif  // VERY_SIMPLE_TEST_H
+
+/**
+ * V1.0: Creation of franework
+ * V1.1: make check(bool) inline, automatically convert expected value type to
+ * actual value type
+ * V1.2: added possibilty to count constructions and destructions of some type
+ * V1.3: tweaks on check for int and double types
+ * V1.4: Adding thread safety in OpenMP programs (not general thread safety, as
+ *       OpenMP and std::thread might not play along)
+ */
\ No newline at end of file
diff --git a/a3_ln2_hybrid/a3_ln2_hybrid.cpp b/a3_ln2_hybrid/a3_ln2_hybrid.cpp
new file mode 100644
index 0000000..d6fc076
--- /dev/null
+++ b/a3_ln2_hybrid/a3_ln2_hybrid.cpp
@@ -0,0 +1,69 @@
+#include <iostream>
+#include <mpi.h>
+#include <omp.h>
+#include "test.h"
+
+void runningHybridTest();
+void computeLn2Test();
+
+// ****************************************************
+// TODO: parallelize this function with MPI and OpenMP
+// ****************************************************
+
+double ln2(int numTerms) {
+  int rank, numProcs;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &numProcs);
+
+  int start = 1 + (numTerms / numProcs) * rank;
+  int end = (numTerms / numProcs) * (rank + 1);
+
+  double localSum = 0;
+  
+  #pragma omp parallel for reduction(+ : localSum)
+  for (int i = start; i < end + 1; ++i) {
+    int sign = 1;
+    if (i % 2 == 0) {
+      sign = -1;
+    }
+    localSum += sign / static_cast<double>(i);
+  }
+
+  double globalSum;
+  MPI_Allreduce(&localSum, &globalSum, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
+
+  return globalSum;
+}
+
+int main(int argc, char* argv[]) {
+  MPI_Init(&argc, &argv);
+  runningHybridTest();
+  computeLn2Test();
+  MPI_Finalize();
+}
+
+// Do not change anything below this line!
+// You may use the tests below to verify that your
+// program works correctly.
+// ****************************************************
+
+// Verify that the program actually runs with MPI and OpenMP
+void runningHybridTest() {
+  int numProc;
+  MPI_Comm_size(MPI_COMM_WORLD, &numProc);
+#pragma omp parallel
+  {
+    int numThreads = omp_get_num_threads();
+    check(numProc, 2);
+    check(numThreads, 2);
+  }
+}
+
+// Verify correct functionality of ln2()
+void computeLn2Test() {
+  check(ln2(4), 0.5833333333333333);
+  check(ln2(8), 0.6345238095238095);
+  check(ln2(12), 0.6532106782106781);
+  check(ln2(100), 0.688172179310195);
+  check(ln2(1e6), 0.6931466805602525);
+}
diff --git a/a3_ln2_hybrid/ln2 b/a3_ln2_hybrid/ln2
new file mode 100644
index 0000000..0206498
Binary files /dev/null and b/a3_ln2_hybrid/ln2 differ
diff --git a/a3_ln2_hybrid/makefile b/a3_ln2_hybrid/makefile
new file mode 100644
index 0000000..8bf29ad
--- /dev/null
+++ b/a3_ln2_hybrid/makefile
@@ -0,0 +1,5 @@
+all: a3_ln2_hybrid.cpp
+	mpicxx a3_ln2_hybrid.cpp -fopenmp -o ln2
+
+run: all
+	mpirun -np 2 -x OMP_NUM_THREADS=2 ./ln2
\ No newline at end of file
diff --git a/a3_ln2_hybrid/test.h b/a3_ln2_hybrid/test.h
new file mode 100644
index 0000000..232be71
--- /dev/null
+++ b/a3_ln2_hybrid/test.h
@@ -0,0 +1,290 @@
+/** test.h, an extremly simple test framework.
+ * Version 1.4
+ * Copyright (C) 2022-2023 Tobias Kreilos, Offenburg University of Applied
+ * Sciences
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * The framework defines a function check(a,b) that can be called with
+ * parameters of different types. The function asserts
+ * that the two paramters are equal (within a certain, predefined range for
+ * floating point numbers) and prints the result of the comparison on the
+ * command line. Additionally a summary of all tests is printed at the end of
+ * the program.
+ * Additionally there is TEST macro, which you can place outside main to group
+ * tests together. Code in the macro is automatically executed at the beginning
+ * of the program.
+ * The file also defines a class InstanceCount, that can be used to
+ * count how many instances of an object are still alive at the end of a
+ * program. To use it, derive your class from InstanceCount<ClassName> and the
+ * message is automatically printed at the end of the program.
+ */
+
+#ifndef VERY_SIMPLE_TEST_H
+  #define VERY_SIMPLE_TEST_H
+
+  #include <cmath>
+  #include <iostream>
+  #include <sstream>
+  #include <atomic>
+
+  /** Simple macro to execute the code that follows the macro (without call from
+   * main)
+   *
+   * Define a class, that is directly instantiated
+   * and contains the test code in the constructor.
+   *
+   * Usage:
+   * TEST(MyTest)
+   * {
+   *    // test code
+   * }
+   */
+  #define TEST(name)              \
+    struct _TestClass##name {     \
+      _TestClass##name();         \
+    } _TestClass##name##Instance; \
+    _TestClass##name::_TestClass##name()
+
+// Use a namespace to hide implementation details
+namespace Test::Detail {
+/**
+ * Make it possible to print the underlying value of class enums with ostream
+ *
+ * The expression typename std::enable_if<std::is_enum<T>::value,
+ * std::ostream>::type decays to ostream if the type T is an enum. Otherwise,
+ * the function is not generated.
+ */
+template <typename T>
+std::ostream& operator<<(
+    typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream,
+    const T& e) {
+  return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
+/**
+ * Convert anything to a string.
+ */
+template <typename T>
+std::string toString(const T& t) {
+  std::ostringstream ss;
+  ss << t;
+  return "\"" + ss.str() + "\"";
+}
+
+/**
+ * Convert bools to string "true" or "false" instead of 0 and 1
+ */
+template <>
+inline std::string toString<bool>(const bool& b) {
+  return b ? "\"true\"" : "\"false\"";
+}
+
+/**
+ * Comparison function for different types
+ */
+template <typename T>
+bool isEqual(const T& t1, const T& t2) {
+  return t1 == t2;
+}
+
+/**
+ * Double values are equal if they differ no more than 1e-12
+ */
+template <>
+inline bool isEqual<double>(const double& expectedValue,
+                            const double& actualValue) {
+  const double epsilon = 1e-12;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * Float values are equal if they differ no more than 1e-6
+ */
+template <>
+inline bool isEqual<float>(const float& expectedValue,
+                           const float& actualValue) {
+  const double epsilon = 1e-6;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * This class realizes some basics of the test framework.
+ * Test summary is printed in the destructor.
+ * Apart from that, the class implements counting of total and failed tests,
+ * comparison of floating point numbers within sensible boundaries and prints
+ * the result of each test on the command line.
+ */
+class Test {
+ public:
+  /**
+   * Test class is a Singleton
+   */
+  static Test& instance() {
+    static Test test;
+    return test;
+  }
+
+  /**
+   * the main entry point for tests. Test two values for equality and output the
+   * result.
+   */
+  template <typename T>
+  bool check(const T& expectedValue, const T& actualValue) {
+    bool testResult = isEqual(expectedValue, actualValue);
+    if (testResult == true) {
+      registerPassingTest();
+  #pragma omp critical
+      std::cout << "Test successful! Expected value == actual value (="
+                << toString(expectedValue) << ")" << std::endl;
+    } else {
+      registerFailingTest();
+  #pragma omp critical
+      std::cout << "Error in test: expected value " << toString(expectedValue)
+                << ", but actual value was " << toString(actualValue)
+                << std::endl;
+    }
+
+    return testResult;
+  }
+
+ private:
+  /**
+   * On destruction, print a summary of all tests.
+   */
+  ~Test() {
+    std::cout << "\n--------------------------------------" << std::endl;
+    std::cout << "Test summary:" << std::endl;
+    std::cout << "Executed tests: " << numTests_ << std::endl;
+    std::cout << "Failed tests: " << numFailedTests_ << std::endl;
+  }
+
+  void registerPassingTest() { numTests_++; }
+
+  void registerFailingTest() {
+    numTests_++;
+    numFailedTests_++;
+  }
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numTests_ = 0;
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numFailedTests_ = 0;
+};
+
+template <typename T>
+class InstanceCounterHelper {
+ public:
+  ~InstanceCounterHelper() {
+    std::cout << "The remaining number of objects of type " << typeid(T).name()
+              << " at the end of the program is " << count;
+    if (count > 0)
+      std::cout << " (NOT zero!)";
+    std::cout << "\nThe total number of objects created was " << total
+              << std::endl;
+  }
+
+  void increment() {
+    count++;
+    total++;
+  }
+
+  void decrement() { count--; }
+
+ private:
+  std::atomic<int> count = 0;
+  std::atomic<int> total = 0;
+};
+
+}  // namespace Test::Detail
+
+/**
+ * Count the instances of a class T.
+ * Result gets printed automatically at the end of the program.
+ * To use it, inherit T from InstanceCounter<T>, e.g.
+ * class MyClass : InstanceCounter<MyClass>
+ */
+template <typename T>
+class InstanceCounter {
+ public:
+  InstanceCounter() { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&) { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&&) { counter().increment(); }
+
+  virtual ~InstanceCounter() { counter().decrement(); }
+
+  Test::Detail::InstanceCounterHelper<T>& counter() {
+    static Test::Detail::InstanceCounterHelper<T> c;
+    return c;
+  }
+};
+
+/**
+ * Check if the expected value is equal to the actual value.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+template <typename T1, typename T2>
+void check(const T1& actualValue, const T2& expectedValue) {
+  const T1& expectedValueCasted{
+      expectedValue};  // allows conversion in general, but avoids narrowing
+                       // conversion
+  Test::Detail::Test::instance().check(expectedValueCasted, actualValue);
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const int& actualValue, const double& expectedValue) {
+  Test::Detail::Test::instance().check(expectedValue,
+                                       static_cast<double>(actualValue));
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const double& actualValue, const int& expectedValue) {
+  Test::Detail::Test::instance().check(static_cast<double>(expectedValue),
+                                       actualValue);
+}
+
+/**
+ * Check if the entered value is true.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+inline void check(bool a) {
+  Test::Detail::Test::instance().check(true, a);
+}
+
+#endif  // VERY_SIMPLE_TEST_H
+
+/**
+ * V1.0: Creation of franework
+ * V1.1: make check(bool) inline, automatically convert expected value type to
+ * actual value type
+ * V1.2: added possibilty to count constructions and destructions of some type
+ * V1.3: tweaks on check for int and double types
+ * V1.4: Adding thread safety in OpenMP programs (not general thread safety, as
+ *       OpenMP and std::thread might not play along)
+ */
\ No newline at end of file
diff --git a/a4_minimum_search/.DS_Store b/a4_minimum_search/.DS_Store
new file mode 100644
index 0000000..5008ddf
Binary files /dev/null and b/a4_minimum_search/.DS_Store differ
diff --git a/a4_minimum_search/a4_min.cpp b/a4_minimum_search/a4_min.cpp
new file mode 100644
index 0000000..2a1b332
--- /dev/null
+++ b/a4_minimum_search/a4_min.cpp
@@ -0,0 +1,73 @@
+#include <iostream>
+#include <cmath>
+#include <functional>
+#include <omp.h>
+#include "test.h"
+
+void findMinimumTest();
+
+// ****************************************************
+// TODO: find and fix the data race in this function
+// ****************************************************
+double findMinimum(std::function<double(double)> f,
+                   double xMin,
+                   double xMax,
+                   int n) {
+
+  double globalMin = f(xMax);
+  double localMin = f(xMax);
+
+#pragma omp parallel firstprivate(localMin) shared(globalMin)
+  {
+    double range = xMax - xMin;
+    double step = range / n;
+
+#pragma omp for schedule(static)
+    for (int i = 0; i < n; ++i) {
+      double x = xMin + step * i;
+      double fx = f(x);
+      if (fx < localMin) {
+        localMin = fx;
+      }
+    }
+
+    #pragma omp critical
+    if (localMin < globalMin) {
+      globalMin = localMin;
+    }
+  }
+
+  return globalMin;
+}
+
+int main() {
+  findMinimumTest();
+}
+
+// Do not change anything below this line!
+// You may use the tests below to verify that your
+// program works correctly.
+// ****************************************************
+
+double f0(double x) {
+  return (x - 2) * (x - 2);
+}
+
+double f1(double x) {
+  return sin(x) + 1. / 5. * x * x * x * x - 3. * (x - 3) * (x - 3);
+};
+
+double f2(double x) {
+  return sin(x) + x * x;
+}
+
+double f3(double x) { 
+  return x*x*x*x - x*x;
+}
+
+void findMinimumTest() {
+  check(findMinimum(f0, -5, 5, 1e6), 0);
+  check(findMinimum(f1, -5, 5, 1e6), -96.68321722021884);
+  check(findMinimum(f2, -5, 5, 1e6), -0.2324655751423368);
+  check(findMinimum(f3, -2, 2, 1e7), -0.25);
+}
\ No newline at end of file
diff --git a/a4_minimum_search/makefile b/a4_minimum_search/makefile
new file mode 100644
index 0000000..5bd1b96
--- /dev/null
+++ b/a4_minimum_search/makefile
@@ -0,0 +1,5 @@
+build: a4_min.cpp
+	g++ -std=c++17 a4_min.cpp -fopenmp -o min
+
+run: build
+	./min
\ No newline at end of file
diff --git a/a4_minimum_search/min b/a4_minimum_search/min
new file mode 100644
index 0000000..eaa3b31
Binary files /dev/null and b/a4_minimum_search/min differ
diff --git a/a4_minimum_search/test.h b/a4_minimum_search/test.h
new file mode 100644
index 0000000..232be71
--- /dev/null
+++ b/a4_minimum_search/test.h
@@ -0,0 +1,290 @@
+/** test.h, an extremly simple test framework.
+ * Version 1.4
+ * Copyright (C) 2022-2023 Tobias Kreilos, Offenburg University of Applied
+ * Sciences
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * The framework defines a function check(a,b) that can be called with
+ * parameters of different types. The function asserts
+ * that the two paramters are equal (within a certain, predefined range for
+ * floating point numbers) and prints the result of the comparison on the
+ * command line. Additionally a summary of all tests is printed at the end of
+ * the program.
+ * Additionally there is TEST macro, which you can place outside main to group
+ * tests together. Code in the macro is automatically executed at the beginning
+ * of the program.
+ * The file also defines a class InstanceCount, that can be used to
+ * count how many instances of an object are still alive at the end of a
+ * program. To use it, derive your class from InstanceCount<ClassName> and the
+ * message is automatically printed at the end of the program.
+ */
+
+#ifndef VERY_SIMPLE_TEST_H
+  #define VERY_SIMPLE_TEST_H
+
+  #include <cmath>
+  #include <iostream>
+  #include <sstream>
+  #include <atomic>
+
+  /** Simple macro to execute the code that follows the macro (without call from
+   * main)
+   *
+   * Define a class, that is directly instantiated
+   * and contains the test code in the constructor.
+   *
+   * Usage:
+   * TEST(MyTest)
+   * {
+   *    // test code
+   * }
+   */
+  #define TEST(name)              \
+    struct _TestClass##name {     \
+      _TestClass##name();         \
+    } _TestClass##name##Instance; \
+    _TestClass##name::_TestClass##name()
+
+// Use a namespace to hide implementation details
+namespace Test::Detail {
+/**
+ * Make it possible to print the underlying value of class enums with ostream
+ *
+ * The expression typename std::enable_if<std::is_enum<T>::value,
+ * std::ostream>::type decays to ostream if the type T is an enum. Otherwise,
+ * the function is not generated.
+ */
+template <typename T>
+std::ostream& operator<<(
+    typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream,
+    const T& e) {
+  return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
+/**
+ * Convert anything to a string.
+ */
+template <typename T>
+std::string toString(const T& t) {
+  std::ostringstream ss;
+  ss << t;
+  return "\"" + ss.str() + "\"";
+}
+
+/**
+ * Convert bools to string "true" or "false" instead of 0 and 1
+ */
+template <>
+inline std::string toString<bool>(const bool& b) {
+  return b ? "\"true\"" : "\"false\"";
+}
+
+/**
+ * Comparison function for different types
+ */
+template <typename T>
+bool isEqual(const T& t1, const T& t2) {
+  return t1 == t2;
+}
+
+/**
+ * Double values are equal if they differ no more than 1e-12
+ */
+template <>
+inline bool isEqual<double>(const double& expectedValue,
+                            const double& actualValue) {
+  const double epsilon = 1e-12;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * Float values are equal if they differ no more than 1e-6
+ */
+template <>
+inline bool isEqual<float>(const float& expectedValue,
+                           const float& actualValue) {
+  const double epsilon = 1e-6;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * This class realizes some basics of the test framework.
+ * Test summary is printed in the destructor.
+ * Apart from that, the class implements counting of total and failed tests,
+ * comparison of floating point numbers within sensible boundaries and prints
+ * the result of each test on the command line.
+ */
+class Test {
+ public:
+  /**
+   * Test class is a Singleton
+   */
+  static Test& instance() {
+    static Test test;
+    return test;
+  }
+
+  /**
+   * the main entry point for tests. Test two values for equality and output the
+   * result.
+   */
+  template <typename T>
+  bool check(const T& expectedValue, const T& actualValue) {
+    bool testResult = isEqual(expectedValue, actualValue);
+    if (testResult == true) {
+      registerPassingTest();
+  #pragma omp critical
+      std::cout << "Test successful! Expected value == actual value (="
+                << toString(expectedValue) << ")" << std::endl;
+    } else {
+      registerFailingTest();
+  #pragma omp critical
+      std::cout << "Error in test: expected value " << toString(expectedValue)
+                << ", but actual value was " << toString(actualValue)
+                << std::endl;
+    }
+
+    return testResult;
+  }
+
+ private:
+  /**
+   * On destruction, print a summary of all tests.
+   */
+  ~Test() {
+    std::cout << "\n--------------------------------------" << std::endl;
+    std::cout << "Test summary:" << std::endl;
+    std::cout << "Executed tests: " << numTests_ << std::endl;
+    std::cout << "Failed tests: " << numFailedTests_ << std::endl;
+  }
+
+  void registerPassingTest() { numTests_++; }
+
+  void registerFailingTest() {
+    numTests_++;
+    numFailedTests_++;
+  }
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numTests_ = 0;
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numFailedTests_ = 0;
+};
+
+template <typename T>
+class InstanceCounterHelper {
+ public:
+  ~InstanceCounterHelper() {
+    std::cout << "The remaining number of objects of type " << typeid(T).name()
+              << " at the end of the program is " << count;
+    if (count > 0)
+      std::cout << " (NOT zero!)";
+    std::cout << "\nThe total number of objects created was " << total
+              << std::endl;
+  }
+
+  void increment() {
+    count++;
+    total++;
+  }
+
+  void decrement() { count--; }
+
+ private:
+  std::atomic<int> count = 0;
+  std::atomic<int> total = 0;
+};
+
+}  // namespace Test::Detail
+
+/**
+ * Count the instances of a class T.
+ * Result gets printed automatically at the end of the program.
+ * To use it, inherit T from InstanceCounter<T>, e.g.
+ * class MyClass : InstanceCounter<MyClass>
+ */
+template <typename T>
+class InstanceCounter {
+ public:
+  InstanceCounter() { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&) { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&&) { counter().increment(); }
+
+  virtual ~InstanceCounter() { counter().decrement(); }
+
+  Test::Detail::InstanceCounterHelper<T>& counter() {
+    static Test::Detail::InstanceCounterHelper<T> c;
+    return c;
+  }
+};
+
+/**
+ * Check if the expected value is equal to the actual value.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+template <typename T1, typename T2>
+void check(const T1& actualValue, const T2& expectedValue) {
+  const T1& expectedValueCasted{
+      expectedValue};  // allows conversion in general, but avoids narrowing
+                       // conversion
+  Test::Detail::Test::instance().check(expectedValueCasted, actualValue);
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const int& actualValue, const double& expectedValue) {
+  Test::Detail::Test::instance().check(expectedValue,
+                                       static_cast<double>(actualValue));
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const double& actualValue, const int& expectedValue) {
+  Test::Detail::Test::instance().check(static_cast<double>(expectedValue),
+                                       actualValue);
+}
+
+/**
+ * Check if the entered value is true.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+inline void check(bool a) {
+  Test::Detail::Test::instance().check(true, a);
+}
+
+#endif  // VERY_SIMPLE_TEST_H
+
+/**
+ * V1.0: Creation of franework
+ * V1.1: make check(bool) inline, automatically convert expected value type to
+ * actual value type
+ * V1.2: added possibilty to count constructions and destructions of some type
+ * V1.3: tweaks on check for int and double types
+ * V1.4: Adding thread safety in OpenMP programs (not general thread safety, as
+ *       OpenMP and std::thread might not play along)
+ */
\ No newline at end of file
diff --git a/a5_mpi_deadlock/.DS_Store b/a5_mpi_deadlock/.DS_Store
new file mode 100644
index 0000000..5008ddf
Binary files /dev/null and b/a5_mpi_deadlock/.DS_Store differ
diff --git a/a5_mpi_deadlock/a5_deadlock.cpp b/a5_mpi_deadlock/a5_deadlock.cpp
new file mode 100644
index 0000000..b493380
--- /dev/null
+++ b/a5_mpi_deadlock/a5_deadlock.cpp
@@ -0,0 +1,49 @@
+#include <mpi.h>
+#include <iostream>
+#include "test.h"
+
+int main(int argc, char* argv[]) {
+  MPI_Init(&argc, &argv);
+
+  int rank, numProc;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &numProc);
+
+  int sendBuf;
+  int recvBuf;
+  int val = 0;
+  MPI_Status status;
+
+  // send and receive message on rank 0
+  if (rank == 0) {
+    sendBuf = 123;
+    MPI_Recv(&recvBuf, 1, MPI_INT, 1, 0, MPI_COMM_WORLD, &status);
+    std::cout << "Rank 0 received " << recvBuf << "\n";
+
+    MPI_Send(&sendBuf, 1, MPI_INT, 1, 0, MPI_COMM_WORLD);
+    std::cout << "Rank 0 sent " << sendBuf << " to rank 1\n";
+
+    check(recvBuf, 456);
+  }
+  
+  // send and receive message on rank 1
+  if (rank == 1) {
+    sendBuf = 456;
+    MPI_Send(&sendBuf, 1, MPI_INT, 0, 0, MPI_COMM_WORLD);
+    std::cout << "Rank 1 sent " << sendBuf << " to rank 0\n";
+
+    MPI_Recv(&recvBuf, 1, MPI_INT, 0, 0, MPI_COMM_WORLD, &status);
+    std::cout << "Rank 1 received " << recvBuf << "\n";
+
+    check(recvBuf, 123);
+  }
+
+  // Broadcast value from rank 0 to all others
+  if (rank == 0) val = 789;
+  MPI_Bcast(&val, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD);
+
+  // Verify that broadcast message arrived correctly everywhere
+  check(val, 789);
+
+  MPI_Finalize();
+}
\ No newline at end of file
diff --git a/a5_mpi_deadlock/deadlock b/a5_mpi_deadlock/deadlock
new file mode 100644
index 0000000..dd7608d
Binary files /dev/null and b/a5_mpi_deadlock/deadlock differ
diff --git a/a5_mpi_deadlock/makefile b/a5_mpi_deadlock/makefile
new file mode 100644
index 0000000..e56bc19
--- /dev/null
+++ b/a5_mpi_deadlock/makefile
@@ -0,0 +1,5 @@
+all: a5_deadlock.cpp
+	mpicxx a5_deadlock.cpp -std=c++17 -o deadlock
+
+run: all
+	mpirun -np 3 ./deadlock
\ No newline at end of file
diff --git a/a5_mpi_deadlock/test.h b/a5_mpi_deadlock/test.h
new file mode 100644
index 0000000..232be71
--- /dev/null
+++ b/a5_mpi_deadlock/test.h
@@ -0,0 +1,290 @@
+/** test.h, an extremly simple test framework.
+ * Version 1.4
+ * Copyright (C) 2022-2023 Tobias Kreilos, Offenburg University of Applied
+ * Sciences
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * The framework defines a function check(a,b) that can be called with
+ * parameters of different types. The function asserts
+ * that the two paramters are equal (within a certain, predefined range for
+ * floating point numbers) and prints the result of the comparison on the
+ * command line. Additionally a summary of all tests is printed at the end of
+ * the program.
+ * Additionally there is TEST macro, which you can place outside main to group
+ * tests together. Code in the macro is automatically executed at the beginning
+ * of the program.
+ * The file also defines a class InstanceCount, that can be used to
+ * count how many instances of an object are still alive at the end of a
+ * program. To use it, derive your class from InstanceCount<ClassName> and the
+ * message is automatically printed at the end of the program.
+ */
+
+#ifndef VERY_SIMPLE_TEST_H
+  #define VERY_SIMPLE_TEST_H
+
+  #include <cmath>
+  #include <iostream>
+  #include <sstream>
+  #include <atomic>
+
+  /** Simple macro to execute the code that follows the macro (without call from
+   * main)
+   *
+   * Define a class, that is directly instantiated
+   * and contains the test code in the constructor.
+   *
+   * Usage:
+   * TEST(MyTest)
+   * {
+   *    // test code
+   * }
+   */
+  #define TEST(name)              \
+    struct _TestClass##name {     \
+      _TestClass##name();         \
+    } _TestClass##name##Instance; \
+    _TestClass##name::_TestClass##name()
+
+// Use a namespace to hide implementation details
+namespace Test::Detail {
+/**
+ * Make it possible to print the underlying value of class enums with ostream
+ *
+ * The expression typename std::enable_if<std::is_enum<T>::value,
+ * std::ostream>::type decays to ostream if the type T is an enum. Otherwise,
+ * the function is not generated.
+ */
+template <typename T>
+std::ostream& operator<<(
+    typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream,
+    const T& e) {
+  return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
+/**
+ * Convert anything to a string.
+ */
+template <typename T>
+std::string toString(const T& t) {
+  std::ostringstream ss;
+  ss << t;
+  return "\"" + ss.str() + "\"";
+}
+
+/**
+ * Convert bools to string "true" or "false" instead of 0 and 1
+ */
+template <>
+inline std::string toString<bool>(const bool& b) {
+  return b ? "\"true\"" : "\"false\"";
+}
+
+/**
+ * Comparison function for different types
+ */
+template <typename T>
+bool isEqual(const T& t1, const T& t2) {
+  return t1 == t2;
+}
+
+/**
+ * Double values are equal if they differ no more than 1e-12
+ */
+template <>
+inline bool isEqual<double>(const double& expectedValue,
+                            const double& actualValue) {
+  const double epsilon = 1e-12;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * Float values are equal if they differ no more than 1e-6
+ */
+template <>
+inline bool isEqual<float>(const float& expectedValue,
+                           const float& actualValue) {
+  const double epsilon = 1e-6;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * This class realizes some basics of the test framework.
+ * Test summary is printed in the destructor.
+ * Apart from that, the class implements counting of total and failed tests,
+ * comparison of floating point numbers within sensible boundaries and prints
+ * the result of each test on the command line.
+ */
+class Test {
+ public:
+  /**
+   * Test class is a Singleton
+   */
+  static Test& instance() {
+    static Test test;
+    return test;
+  }
+
+  /**
+   * the main entry point for tests. Test two values for equality and output the
+   * result.
+   */
+  template <typename T>
+  bool check(const T& expectedValue, const T& actualValue) {
+    bool testResult = isEqual(expectedValue, actualValue);
+    if (testResult == true) {
+      registerPassingTest();
+  #pragma omp critical
+      std::cout << "Test successful! Expected value == actual value (="
+                << toString(expectedValue) << ")" << std::endl;
+    } else {
+      registerFailingTest();
+  #pragma omp critical
+      std::cout << "Error in test: expected value " << toString(expectedValue)
+                << ", but actual value was " << toString(actualValue)
+                << std::endl;
+    }
+
+    return testResult;
+  }
+
+ private:
+  /**
+   * On destruction, print a summary of all tests.
+   */
+  ~Test() {
+    std::cout << "\n--------------------------------------" << std::endl;
+    std::cout << "Test summary:" << std::endl;
+    std::cout << "Executed tests: " << numTests_ << std::endl;
+    std::cout << "Failed tests: " << numFailedTests_ << std::endl;
+  }
+
+  void registerPassingTest() { numTests_++; }
+
+  void registerFailingTest() {
+    numTests_++;
+    numFailedTests_++;
+  }
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numTests_ = 0;
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numFailedTests_ = 0;
+};
+
+template <typename T>
+class InstanceCounterHelper {
+ public:
+  ~InstanceCounterHelper() {
+    std::cout << "The remaining number of objects of type " << typeid(T).name()
+              << " at the end of the program is " << count;
+    if (count > 0)
+      std::cout << " (NOT zero!)";
+    std::cout << "\nThe total number of objects created was " << total
+              << std::endl;
+  }
+
+  void increment() {
+    count++;
+    total++;
+  }
+
+  void decrement() { count--; }
+
+ private:
+  std::atomic<int> count = 0;
+  std::atomic<int> total = 0;
+};
+
+}  // namespace Test::Detail
+
+/**
+ * Count the instances of a class T.
+ * Result gets printed automatically at the end of the program.
+ * To use it, inherit T from InstanceCounter<T>, e.g.
+ * class MyClass : InstanceCounter<MyClass>
+ */
+template <typename T>
+class InstanceCounter {
+ public:
+  InstanceCounter() { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&) { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&&) { counter().increment(); }
+
+  virtual ~InstanceCounter() { counter().decrement(); }
+
+  Test::Detail::InstanceCounterHelper<T>& counter() {
+    static Test::Detail::InstanceCounterHelper<T> c;
+    return c;
+  }
+};
+
+/**
+ * Check if the expected value is equal to the actual value.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+template <typename T1, typename T2>
+void check(const T1& actualValue, const T2& expectedValue) {
+  const T1& expectedValueCasted{
+      expectedValue};  // allows conversion in general, but avoids narrowing
+                       // conversion
+  Test::Detail::Test::instance().check(expectedValueCasted, actualValue);
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const int& actualValue, const double& expectedValue) {
+  Test::Detail::Test::instance().check(expectedValue,
+                                       static_cast<double>(actualValue));
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const double& actualValue, const int& expectedValue) {
+  Test::Detail::Test::instance().check(static_cast<double>(expectedValue),
+                                       actualValue);
+}
+
+/**
+ * Check if the entered value is true.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+inline void check(bool a) {
+  Test::Detail::Test::instance().check(true, a);
+}
+
+#endif  // VERY_SIMPLE_TEST_H
+
+/**
+ * V1.0: Creation of franework
+ * V1.1: make check(bool) inline, automatically convert expected value type to
+ * actual value type
+ * V1.2: added possibilty to count constructions and destructions of some type
+ * V1.3: tweaks on check for int and double types
+ * V1.4: Adding thread safety in OpenMP programs (not general thread safety, as
+ *       OpenMP and std::thread might not play along)
+ */
\ No newline at end of file
diff --git a/a6_send_column/.DS_Store b/a6_send_column/.DS_Store
new file mode 100644
index 0000000..5008ddf
Binary files /dev/null and b/a6_send_column/.DS_Store differ
diff --git a/a6_send_column/a6_send_column.cpp b/a6_send_column/a6_send_column.cpp
new file mode 100644
index 0000000..4b08d3f
--- /dev/null
+++ b/a6_send_column/a6_send_column.cpp
@@ -0,0 +1,98 @@
+#include <iostream>
+#include <cmath>
+#include <mpi.h>
+#include <vector>
+#include "test.h"
+#include "matrix.h"
+
+using namespace HPC;
+
+// For simplicity, store rank in a global variable
+int rank;
+
+// ****************************************************
+// TODO: modify this function to use a custom data
+// type instead of sending each entry separately.
+// ****************************************************
+
+// Send one column of the matrix from rank 0 to rank 1
+void sendColumn(Matrix& m, int col) {
+
+  // Store MPI_Reqeuests
+  std::vector<MPI_Request> req(m.dim1());
+
+  // Send/receive each entry of the column separately
+  for (int i=0; i<m.dim1(); ++i) {
+    if (rank == 0) {
+      MPI_Isend(&m(i, col), 1, MPI_DOUBLE, 1, i, MPI_COMM_WORLD, &req[i]);
+    }
+    else if (rank == 1) {
+      MPI_Irecv(&m(i, col), 1, MPI_DOUBLE, 0, i, MPI_COMM_WORLD, &req[i]);
+    }
+  }
+
+  // Wait for all data to be received
+  std::vector<MPI_Status> stat(m.dim1());
+  MPI_Waitall(req.size(), req.data(), stat.data());
+}
+
+// Do not change anything below this line!
+// You may use the tests below to verify that your
+// program works correctly.
+// ****************************************************
+
+// Create a matrix with some contents
+Matrix createMatrix(int n) {
+  Matrix m(n);
+  for (int i = 0; i < n; ++i) {
+    for (int j = 0; j < n; ++j) {
+      m(i, j) = 2 * i + i * j + 1;
+    }
+  }
+  return m;
+}
+
+void sendColumnTest() {
+  int n = 3;
+
+  Matrix m(n);
+  if (rank == 0) {
+    m = createMatrix(n);
+  }
+
+  sendColumn(m, 1);
+
+  if (rank == 0) {
+    check(m(0, 0), 1);
+    check(m(0, 1), 1);
+    check(m(0, 2), 1);
+    check(m(1, 0), 3);
+    check(m(1, 1), 4);
+    check(m(1, 2), 5);
+    check(m(2, 0), 5);
+    check(m(2, 1), 7);
+    check(m(2, 2), 9);
+  }
+
+  if (rank == 1) {
+    check(m(0, 0), 0);
+    check(m(0, 1), 1);
+    check(m(0, 2), 0);
+    check(m(1, 0), 0);
+    check(m(1, 1), 4);
+    check(m(1, 2), 0);
+    check(m(2, 0), 0);
+    check(m(2, 1), 7);
+    check(m(2, 2), 0);
+  }
+}
+
+
+int main(int argc, char* argv[]) {
+  MPI_Init(&argc, &argv);
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  sendColumnTest();
+
+  MPI_Finalize();
+}
\ No newline at end of file
diff --git a/a6_send_column/makefile b/a6_send_column/makefile
new file mode 100644
index 0000000..8e69866
--- /dev/null
+++ b/a6_send_column/makefile
@@ -0,0 +1,5 @@
+build: a6_send_column.cpp test.h matrix.h
+	mpicxx -std=c++17 a6_send_column.cpp -o send-column
+
+run: build
+	mpirun -np 2 -x OMP_NUM_THREADS=2 ./send-column
\ No newline at end of file
diff --git a/a6_send_column/matrix.h b/a6_send_column/matrix.h
new file mode 100644
index 0000000..b8caacc
--- /dev/null
+++ b/a6_send_column/matrix.h
@@ -0,0 +1,324 @@
+/**
+ * matrix.h a very simplistic class for m times n matrices.
+ */
+
+#ifndef MATRIX_H
+#define MATRIX_H
+
+#include <vector>
+#include <iostream>
+#include <iomanip>
+#include <cmath>
+
+namespace HPC {
+
+// A very simplistic vector class for vectors of size n
+class Vector {
+ public:
+  // constructors
+  Vector(int n) : n_(n), data_(n_, 0) {}
+  Vector(const Vector& other) = default;
+  Vector(Vector&& other) = default;
+  ~Vector() = default;
+
+  // assignment operators
+  Vector& operator=(const Vector& other) = default;
+  Vector& operator=(Vector&& other) = default;
+
+  // element access
+  double& operator()(int i) { return data_[i]; }
+  const double& operator()(int i) const { return data_[i]; }
+
+  // getter functions for the dimensions
+  int dim() const { return n_; }
+
+  // comparison operators
+  bool operator==(const Vector& b) { return (data_ == b.data_); }
+  bool operator!=(const Vector& b) { return (data_ != b.data_); }
+
+  // addition, substraction, multiplication with scalars
+  Vector& operator+=(const Vector& b) {
+    for (int i = 0; i < n_; ++i) {
+      operator()(i) += b(i);
+    }
+    return *this;
+  }
+
+  Vector& operator-=(const Vector& b) {
+    for (int i = 0; i < n_; ++i) {
+      operator()(i) -= b(i);
+    }
+    return *this;
+  }
+
+  Vector& operator*=(double x) {
+    for (int i = 0; i < n_; ++i) {
+      operator()(i) *= x;
+    }
+    return *this;
+  }
+
+  Vector& operator/=(double x) {
+    for (int i = 0; i < n_; ++i) {
+      operator()(i) /= x;
+    }
+
+    return *this;
+  }
+
+  double dot(const Vector& other) const {
+    double sum = 0;
+    for (int i = 0; i < n_; ++i) {
+      sum += operator()(i) * other(i);
+    }
+    return sum;
+  }
+
+ private:
+  int n_;                     // vector dimension
+  std::vector<double> data_;  // the vectors entries
+};
+
+inline double dot(const Vector& v1, const Vector& v2) {
+  return v1.dot(v2);
+}
+
+// Print the vector as a table
+inline std::ostream& operator<<(std::ostream& os, const Vector& a) {
+  const int width = 10;
+  const int precision = 4;
+
+  const auto originalPrecision = os.precision();
+  os << std::setprecision(precision);
+
+  for (int i = 0; i < a.dim(); ++i) {
+    os << std::setw(width) << a(i) << " ";
+  }
+
+  os << "\n";
+
+  os << std::setprecision(originalPrecision);
+  return os;
+}
+
+// A very simple class for m times n matrices
+class Matrix {
+ public:
+  // constructors
+  Matrix() : Matrix (0, 0) {}
+  Matrix(int m, int n) : m_(m), n_(n), data_(m_ * n_, 0) {}
+  Matrix(std::pair<int, int> dim) : Matrix(dim.first, dim.second) {}
+  Matrix(int n) : Matrix(n, n) {}
+  Matrix(const Matrix& other) = default;
+  Matrix(Matrix&& other) = default;
+  ~Matrix() = default;
+
+  // assignment operators
+  Matrix& operator=(const Matrix& other) = default;
+  Matrix& operator=(Matrix&& other) = default;
+
+  // element access
+  double& operator()(int i, int j) { return data_[i * n_ + j]; }
+  const double& operator()(int i, int j) const { return data_[i * n_ + j]; }
+
+  // getter functions for the dimensions
+  std::pair<int, int> dim() const { return std::pair<int, int>(m_, n_); }
+  int dim1() const { return m_; }
+  int dim2() const { return n_; }
+  int numEntries() const { return data_.size(); }
+
+  // comparison operators
+  bool operator==(const Matrix& b) { return (data_ == b.data_); }
+  bool operator!=(const Matrix& b) { return (data_ != b.data_); }
+
+  // addition, substraction, multiplication with scalars
+  Matrix& operator+=(const Matrix& b) {
+    for (int i = 0; i < m_; ++i) {
+      for (int j = 0; j < n_; ++j) {
+        operator()(i, j) += b(i, j);
+      }
+    }
+    return *this;
+  }
+
+  Matrix& operator-=(const Matrix& b) {
+    for (int i = 0; i < m_; ++i) {
+      for (int j = 0; j < n_; ++j) {
+        operator()(i, j) -= b(i, j);
+      }
+    }
+    return *this;
+  }
+
+  Matrix& operator*=(double x) {
+    for (int i = 0; i < m_; ++i) {
+      for (int j = 0; j < n_; ++j) {
+        operator()(i, j) *= x;
+      }
+    }
+    return *this;
+  }
+
+  Matrix& operator/=(double x) {
+    for (int i = 0; i < m_; ++i) {
+      for (int j = 0; j < n_; ++j) {
+        operator()(i, j) /= x;
+      }
+    }
+    return *this;
+  }
+
+ public:
+  int m_;                     // first dimension
+  int n_;                     // second dimension
+  std::vector<double> data_;  // the matrix' entries
+};
+
+// Print the matrix as a table
+inline std::ostream& operator<<(std::ostream& os, const Matrix& a) {
+  const int width = 10;
+  const int precision = 4;
+
+  const auto originalPrecision = os.precision();
+  os << std::setprecision(precision);
+
+  for (int i = 0; i < a.dim1(); ++i) {
+    for (int j = 0; j < a.dim2(); ++j) {
+      os << std::setw(width) << a(i, j) << " ";
+    }
+    if (i != a.dim1() - 1)
+      os << "\n";
+  }
+
+  os << std::setprecision(originalPrecision);
+  return os;
+}
+
+inline Matrix operator*(const Matrix& a, const Matrix& b) {
+  if (a.dim2() == b.dim1()) {
+    int m = a.dim1();
+    int n = a.dim2();
+    int p = b.dim2();
+    Matrix c(m, p);
+    for (int i = 0; i < m; ++i) {
+      for (int j = 0; j < p; ++j) {
+        for (int k = 0; k < n; ++k) {
+          c(i, j) += a(i, k) * b(k, j);
+        }
+      }
+    }
+    return c;
+  } else {
+    return Matrix(0, 0);
+  }
+}
+
+inline bool equalWithinRange(const Matrix& a, const Matrix& b, double eps = 1e-12) {
+  if (a.dim2() != b.dim1())
+    return false;
+
+  int m = a.dim1();
+  int n = a.dim2();
+  for (int i = 0; i < m; ++i) {
+    for (int j = 0; j < n; ++j) {
+      if (fabs(a(i, j) - b(i, j)) > eps) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+// A very simple class for "3D-Matrices" (tensors) with dimension l x m x n
+class Matrix3D {
+ public:
+  // constructors
+  Matrix3D(int l, int m, int n) : l_(l), m_(m), n_(n), data_(l) {
+    for (int i = 0; i < l_; ++i) {
+      data_[i] = std::vector<std::vector<double>>(m_);
+      for (int j = 0; j < m_; ++j) {
+        data_[i][j] = std::vector<double>(n_, 0);
+      }
+    }
+  }
+  Matrix3D(int n) : Matrix3D(n, n, n) {}
+  Matrix3D(const Matrix3D& other) = default;
+  Matrix3D(Matrix3D&& other) = default;
+  ~Matrix3D() = default;
+
+  // assignment operators
+  Matrix3D& operator=(const Matrix3D& other) = default;
+  Matrix3D& operator=(Matrix3D&& other) = default;
+
+  // element access
+  double& operator()(int i, int j, int k) { return data_[i][j][k]; }
+  const double& operator()(int i, int j, int k) const { return data_[i][j][k]; }
+
+  // getter functions for the dimensions
+  int dim1() const { return l_; }
+  int dim2() const { return m_; }
+  int dim3() const { return n_; }
+
+  // comparison operators
+  bool operator==(const Matrix3D& b) { return (data_ == b.data_); }
+  bool operator!=(const Matrix3D& b) { return (data_ != b.data_); }
+
+  // addition
+  Matrix3D& operator+=(const Matrix3D& b) {
+    for (int i = 0; i < l_; ++i) {
+      for (int j = 0; j < m_; ++j) {
+        for (int k = 0; k < n_; ++k) {
+          operator()(i, j, k) += b(i, j, k);
+        }
+      }
+    }
+    return *this;
+  }
+
+  // substraction
+  Matrix3D& operator-=(const Matrix3D& b) {
+    for (int i = 0; i < l_; ++i) {
+      for (int j = 0; j < m_; ++j) {
+        for (int k = 0; k < n_; ++k) {
+          operator()(i, j, k) -= b(i, j, k);
+        }
+      }
+    }
+    return *this;
+  }
+
+  // scalar multiplication
+  Matrix3D& operator*=(double x) {
+    for (int i = 0; i < l_; ++i) {
+      for (int j = 0; j < m_; ++j) {
+        for (int k = 0; k < n_; ++k) {
+          operator()(i, j, k) *= x;
+        }
+      }
+    }
+    return *this;
+  }
+
+  // scalar division
+  Matrix3D& operator/=(double x) {
+    for (int i = 0; i < l_; ++i) {
+      for (int j = 0; j < m_; ++j) {
+        for (int k = 0; k < n_; ++k) {
+          operator()(i, j, k) /= x;
+        }
+      }
+    }
+    return *this;
+  }
+
+ private:
+  int l_;                                               // first dimension
+  int m_;                                               // second dimension
+  int n_;                                               // third dimension
+  std::vector<std::vector<std::vector<double>>> data_;  // the tensors' entries
+};
+
+}  // namespace HPC
+
+#endif  // MATRIX_H
\ No newline at end of file
diff --git a/a6_send_column/send-column b/a6_send_column/send-column
new file mode 100644
index 0000000..fac0594
Binary files /dev/null and b/a6_send_column/send-column differ
diff --git a/a6_send_column/test.h b/a6_send_column/test.h
new file mode 100644
index 0000000..232be71
--- /dev/null
+++ b/a6_send_column/test.h
@@ -0,0 +1,290 @@
+/** test.h, an extremly simple test framework.
+ * Version 1.4
+ * Copyright (C) 2022-2023 Tobias Kreilos, Offenburg University of Applied
+ * Sciences
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * The framework defines a function check(a,b) that can be called with
+ * parameters of different types. The function asserts
+ * that the two paramters are equal (within a certain, predefined range for
+ * floating point numbers) and prints the result of the comparison on the
+ * command line. Additionally a summary of all tests is printed at the end of
+ * the program.
+ * Additionally there is TEST macro, which you can place outside main to group
+ * tests together. Code in the macro is automatically executed at the beginning
+ * of the program.
+ * The file also defines a class InstanceCount, that can be used to
+ * count how many instances of an object are still alive at the end of a
+ * program. To use it, derive your class from InstanceCount<ClassName> and the
+ * message is automatically printed at the end of the program.
+ */
+
+#ifndef VERY_SIMPLE_TEST_H
+  #define VERY_SIMPLE_TEST_H
+
+  #include <cmath>
+  #include <iostream>
+  #include <sstream>
+  #include <atomic>
+
+  /** Simple macro to execute the code that follows the macro (without call from
+   * main)
+   *
+   * Define a class, that is directly instantiated
+   * and contains the test code in the constructor.
+   *
+   * Usage:
+   * TEST(MyTest)
+   * {
+   *    // test code
+   * }
+   */
+  #define TEST(name)              \
+    struct _TestClass##name {     \
+      _TestClass##name();         \
+    } _TestClass##name##Instance; \
+    _TestClass##name::_TestClass##name()
+
+// Use a namespace to hide implementation details
+namespace Test::Detail {
+/**
+ * Make it possible to print the underlying value of class enums with ostream
+ *
+ * The expression typename std::enable_if<std::is_enum<T>::value,
+ * std::ostream>::type decays to ostream if the type T is an enum. Otherwise,
+ * the function is not generated.
+ */
+template <typename T>
+std::ostream& operator<<(
+    typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream,
+    const T& e) {
+  return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
+/**
+ * Convert anything to a string.
+ */
+template <typename T>
+std::string toString(const T& t) {
+  std::ostringstream ss;
+  ss << t;
+  return "\"" + ss.str() + "\"";
+}
+
+/**
+ * Convert bools to string "true" or "false" instead of 0 and 1
+ */
+template <>
+inline std::string toString<bool>(const bool& b) {
+  return b ? "\"true\"" : "\"false\"";
+}
+
+/**
+ * Comparison function for different types
+ */
+template <typename T>
+bool isEqual(const T& t1, const T& t2) {
+  return t1 == t2;
+}
+
+/**
+ * Double values are equal if they differ no more than 1e-12
+ */
+template <>
+inline bool isEqual<double>(const double& expectedValue,
+                            const double& actualValue) {
+  const double epsilon = 1e-12;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * Float values are equal if they differ no more than 1e-6
+ */
+template <>
+inline bool isEqual<float>(const float& expectedValue,
+                           const float& actualValue) {
+  const double epsilon = 1e-6;
+  const double distance = fabs(actualValue - expectedValue);
+  return (distance < epsilon);
+}
+
+/**
+ * This class realizes some basics of the test framework.
+ * Test summary is printed in the destructor.
+ * Apart from that, the class implements counting of total and failed tests,
+ * comparison of floating point numbers within sensible boundaries and prints
+ * the result of each test on the command line.
+ */
+class Test {
+ public:
+  /**
+   * Test class is a Singleton
+   */
+  static Test& instance() {
+    static Test test;
+    return test;
+  }
+
+  /**
+   * the main entry point for tests. Test two values for equality and output the
+   * result.
+   */
+  template <typename T>
+  bool check(const T& expectedValue, const T& actualValue) {
+    bool testResult = isEqual(expectedValue, actualValue);
+    if (testResult == true) {
+      registerPassingTest();
+  #pragma omp critical
+      std::cout << "Test successful! Expected value == actual value (="
+                << toString(expectedValue) << ")" << std::endl;
+    } else {
+      registerFailingTest();
+  #pragma omp critical
+      std::cout << "Error in test: expected value " << toString(expectedValue)
+                << ", but actual value was " << toString(actualValue)
+                << std::endl;
+    }
+
+    return testResult;
+  }
+
+ private:
+  /**
+   * On destruction, print a summary of all tests.
+   */
+  ~Test() {
+    std::cout << "\n--------------------------------------" << std::endl;
+    std::cout << "Test summary:" << std::endl;
+    std::cout << "Executed tests: " << numTests_ << std::endl;
+    std::cout << "Failed tests: " << numFailedTests_ << std::endl;
+  }
+
+  void registerPassingTest() { numTests_++; }
+
+  void registerFailingTest() {
+    numTests_++;
+    numFailedTests_++;
+  }
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numTests_ = 0;
+
+  /**
+   * For statistics
+   */
+  std::atomic<int> numFailedTests_ = 0;
+};
+
+template <typename T>
+class InstanceCounterHelper {
+ public:
+  ~InstanceCounterHelper() {
+    std::cout << "The remaining number of objects of type " << typeid(T).name()
+              << " at the end of the program is " << count;
+    if (count > 0)
+      std::cout << " (NOT zero!)";
+    std::cout << "\nThe total number of objects created was " << total
+              << std::endl;
+  }
+
+  void increment() {
+    count++;
+    total++;
+  }
+
+  void decrement() { count--; }
+
+ private:
+  std::atomic<int> count = 0;
+  std::atomic<int> total = 0;
+};
+
+}  // namespace Test::Detail
+
+/**
+ * Count the instances of a class T.
+ * Result gets printed automatically at the end of the program.
+ * To use it, inherit T from InstanceCounter<T>, e.g.
+ * class MyClass : InstanceCounter<MyClass>
+ */
+template <typename T>
+class InstanceCounter {
+ public:
+  InstanceCounter() { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&) { counter().increment(); }
+
+  InstanceCounter(const InstanceCounter&&) { counter().increment(); }
+
+  virtual ~InstanceCounter() { counter().decrement(); }
+
+  Test::Detail::InstanceCounterHelper<T>& counter() {
+    static Test::Detail::InstanceCounterHelper<T> c;
+    return c;
+  }
+};
+
+/**
+ * Check if the expected value is equal to the actual value.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+template <typename T1, typename T2>
+void check(const T1& actualValue, const T2& expectedValue) {
+  const T1& expectedValueCasted{
+      expectedValue};  // allows conversion in general, but avoids narrowing
+                       // conversion
+  Test::Detail::Test::instance().check(expectedValueCasted, actualValue);
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const int& actualValue, const double& expectedValue) {
+  Test::Detail::Test::instance().check(expectedValue,
+                                       static_cast<double>(actualValue));
+}
+
+// allow conversion from int to double explicitely
+template <>
+inline void check(const double& actualValue, const int& expectedValue) {
+  Test::Detail::Test::instance().check(static_cast<double>(expectedValue),
+                                       actualValue);
+}
+
+/**
+ * Check if the entered value is true.
+ * Result is printed on the command line and at the end of the program, a
+ * summary of all tests is printed.
+ */
+inline void check(bool a) {
+  Test::Detail::Test::instance().check(true, a);
+}
+
+#endif  // VERY_SIMPLE_TEST_H
+
+/**
+ * V1.0: Creation of franework
+ * V1.1: make check(bool) inline, automatically convert expected value type to
+ * actual value type
+ * V1.2: added possibilty to count constructions and destructions of some type
+ * V1.3: tweaks on check for int and double types
+ * V1.4: Adding thread safety in OpenMP programs (not general thread safety, as
+ *       OpenMP and std::thread might not play along)
+ */
\ No newline at end of file