ping_pong.cc
5454280b8282master

ping_pong.cc
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			#include "print_size.hh"
			#include <chrono>
			#include <iomanip>
			#include <iostream>
			#include <mpi.h>
			#include <vector>

			void fill_buffer(std::vector<int> &buf, size_t size) {
			buf.resize(size);
			for (auto &v : buf) {
			v = 0;
			}
			}

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

			int main() {
			int prank, psize;
			const auto N{30};
			size_t REP{1000};

			MPI_Init(NULL, NULL);
			MPI_Comm_rank(MPI_COMM_WORLD, &prank);
			MPI_Comm_size(MPI_COMM_WORLD, &psize);

			std::vector<int> buf;
			auto partner = (prank + 1) % psize;

			for (size_t n = 0; n < N; ++n) {
			auto size = 1 << n;
			fill_buffer(buf, size);

			if (size > 256)
			REP = 1;

			auto t_start = clk::now();
			for (size_t repetition = 0; repetition < REP; ++repetition) {
			if (prank == 0) {
			MPI_Send(buf.data(), buf.size(), MPI_INT, partner, 0, MPI_COMM_WORLD);
			MPI_Recv(buf.data(), buf.size(), MPI_INT, partner, 0, MPI_COMM_WORLD,
			MPI_STATUS_IGNORE);
			} else {
			MPI_Recv(buf.data(), buf.size(), MPI_INT, partner, 0, MPI_COMM_WORLD,
			MPI_STATUS_IGNORE);
			MPI_Send(buf.data(), buf.size(), MPI_INT, partner, 0, MPI_COMM_WORLD);
			}
			}
			second time = clk::now() - t_start;

			if (prank == 0) {
			auto size_b = size * sizeof(int);
			auto time_s = time.count() / REP / 2.;
			std::cout << "PingPong"
			<< " size: " << std::setw(10) << printHuman(size_b, "B", 2)
			<< " time: " << std::setw(10) << printHuman(time_s, "s")
			<< " bandwidth: " << std::setw(10)
			<< printHuman(size_b / time_s, "B/s") << std::endl;
			}
			}

			MPI_Finalize();

			return 0;
			}