			#include <chrono>
			#include <cmath>
			#include <cstdio>
			#include <omp.h>
			#include <vector>

			using clk = std::chrono::high_resolution_clock;
			using second = std::chrono::duration<double>;
			using time_point = std::chrono::time_point<clk>;

			int main() {
			int N = 2000;
			std::vector<double> A(N * N), B(N * N), C(N * N);

			for (auto &a : A)
			a = 1.0;

			for (auto &b : B)
			b = 2.0;

			for (auto &c : C)
			c = 0.0;

			auto verif = [&](auto &&A) {
			double sum = 0.;
			for (auto &a : A)
			sum += a;
			return sum;
			};

			auto nthreads = omp_get_max_threads();

			auto t1 = clk::now();
			#pragma omp parallel for collapse(1) schedule(static, N / nthreads)
			for (int i = 0; i < N; ++i)
			for (int j = 0; j < N; ++j)
			for (int k = 0; k < N; ++k)
			C[i * N + j] += A[i * N + k] * B[k * N + j];

			second elapsed = clk::now() - t1;

			std::printf("DGEMM with %i threads, collapse(1): %g GFLOP/s (verif %g)\n",
			nthreads, ((2. * N * N * N) / elapsed.count() / 1e8),
			verif(C) / (1. * N * N * N));

			return 0;
			}

R11821/examples/openmp/dgemm.cc
d3f2ecb7dd14master

dgemm.cc
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