Pushing everything again, accidentally deleted my remote repository

ex5/ex5_3/goldbach.h

@@ -0,0 +1,45 @@
+#pragma once
+#include "mayer_primes.h"
+#include <cassert>
+#include <vector>
+
+
+/**
+  This function returns the number of possible decompositions of an integer into a sum of two prime numbers.
+  @param[in]    k            first integer
+  @param[out]   count        number of decompositions
+*/
+size_t single_goldbach(size_t k);
+
+
+/**
+  This function returns the number of possible decompositions into a sum of two prime numbers of all even integers in the interval [4,n].
+  @param[in]    n                   upper integer bound
+  @param[out]   count_vector        vector containing the number of decompositions for a natural number the corresponding index
+*/
+std::vector<size_t> count_goldbach(size_t n);
+
+
+/** 	 Vector @p b adds its elements to vector @p a .
+	@param[in] a	vector
+	@param[in] b	vector
+	@return 	     a+=b componentwise
+*/
+template<class T>
+std::vector<T> &operator+=(std::vector<T> &a, std::vector<T> const &b)
+{
+    assert(a.size()==b.size());
+    for (size_t k = 0; k < a.size(); ++k) {
+        a[k] += b[k];
+    }
+    return a;
+}
+
+// Declare the reduction operation in OpenMP for an STL-vector
+//   omp_out += omp_in  requires operator+=(vector<int> &, vector<int> const &) from above
+// ------------------------------------------------------------
+// https://scc.ustc.edu.cn/zlsc/tc4600/intel/2016.0.109/compiler_c/common/core/GUID-7312910C-D175-4544-99C5-29C12D980744.htm
+// https://gist.github.com/eruffaldi/7180bdec4c8c9a11f019dd0ba9a2d68c
+// https://stackoverflow.com/questions/29633531/user-defined-reduction-on-vector-of-varying-size
+//  see also p.74ff in  https://www.fz-juelich.de/ias/jsc/EN/AboutUs/Staff/Hagemeier_A/docs-parallel-programming/OpenMP-Slides.pdf
+#pragma omp declare reduction(VecAdd : std::vector<size_t>  : omp_out += omp_in) initializer (omp_priv=omp_orig)