Task 2 (Asynchronous 2D Jacobi Iteration) Assignment

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#include <iostream> #include <cstdint> #include <vector> #include <limits> #include <string> #include <algorithm> #include <cmath> #include <assert.h> #include <mpi.h> #include "include/bitmap_IO.hpp" // sponsored by stack overflow: http://stackoverflow.com/questions/440133 std::string random_string(size_t length) { auto randchar = []() -> char { const char charset[] = "0123456789" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz"; return charset[ rand() % (sizeof(charset) - 1)]; }; srand(time(0)); std::string str(length, 0); std::generate_n(str.begin(), length, randchar); return str; } int main (int argc, char * argv[]) { MPI::Init (argc, argv); const uint64_t height = 3*4*5*6+2; const uint64_t width = 2*3*4*5*6+2; const uint64_t num_ranks = MPI::COMM_WORLD.Get_size(); const uint64_t rank = MPI::COMM_WORLD.Get_rank(); const uint64_t radix = uint64_t(std::sqrt(num_ranks)); const uint64_t verti = rank / radix; const uint64_t horiz = rank % radix; const bool is_root = rank == 0; assert(num_ranks == radix*radix); assert((height-2) % radix == 0); assert((width -2) % radix == 0); const uint64_t local_height = (height-2)/radix+2; const uint64_t local_width = (width -2)/radix+2; std::vector<double> image(height*width*is_root); std::vector<double> ying(local_height*local_width, 0); std::vector<double> yang(local_height*local_width, 0); // make indexing great again! auto at = [&] (const uint64_t& row, const uint64_t& col) { return row*width+col; }; auto local_at = [&] (const uint64_t& row, const uint64_t& col) { return row*local_width+col; }; if (is_root) { // draw a checkerboard const uint64_t stride = 181; for (uint64_t row = 0; row < height; ++row) for (uint64_t col = 0; col < width; ++col) image[at(row, col)] = (row/stride + col/stride) % 2; } ////////////////////////////////////////////////////////////////////////// // SCATTER ////////////////////////////////////////////////////////////////////////// // create tile data type MPI::Datatype tile_t = MPI::DOUBLE.Create_vector (local_height, local_width , width) .Create_resized(0, sizeof(double)); tile_t.Commit(); int32_t counts[num_ranks], displs[num_ranks]; for (uint64_t proc = 0; proc < num_ranks; ++proc) { const uint64_t i = proc / radix, j = proc % radix; counts[proc] = 1; displs[proc] = i*(local_height-2)*width+j*(local_width-2); } // scatter the tiles MPI::COMM_WORLD.Scatterv(image.data(), counts, displs, tile_t, ying.data(), local_height*local_width, MPI::DOUBLE, 0); ////////////////////////////////////////////////////////////////////////// // FIXPOINT COMPUTATION ////////////////////////////////////////////////////////////////////////// auto update = [&] (const uint64_t& row, const uint64_t& col) { return 0.25*(ying[local_at(row+1, col)] + ying[local_at(row-1, col)] + ying[local_at(row, col+1)] + ying[local_at(row, col-1)]); };

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// relax every pixel in the interior for (uint64_t row = 2; row < local_height-2; ++row) for (uint64_t col = 2; col < local_width-2; ++col) yang[local_at(row, col)] = update(row, col); // Wait until data received req[1].Wait(); req[3].Wait(); req[5].Wait(); req[7].Wait(); // fix the borders for (uint64_t col = 2; col < local_width-2; ++col) yang[local_at(1, col)] = update(1, col); for (uint64_t col = 2; col < local_width-2; ++col) yang[local_at(local_height-2, col)] = update(local_height-2, col); for (uint64_t row = 1; row < local_height-1; ++row) yang[local_at(row, 1)] = update(row, 1); for (uint64_t row = 1; row < local_height-1; ++row) yang[local_at(row, local_width-2)] = update(row, local_width-2); // Wait until data send req[0].Wait(); req[2].Wait(); req[4].Wait(); req[6].Wait(); double local_error = 0; for (uint64_t row = 1; row < local_height-1; ++row) { for (uint64_t col = 1; col < local_width-1; ++col) { const double residue = ying[local_at(row,col)] - yang[local_at(row, col)]; local_error += residue*residue; ying[local_at(row,col)] = yang[local_at(row, col)]; } } // every process needs the same error MPI::COMM_WORLD.Allreduce(&local_error, &error, 1, MPI::DOUBLE, MPI::SUM); // status updates every print_every iteration if (counter++ % print_every == print_every-1 && is_root) std::cout << "# Squared error after " << counter << " iterations: " << error << std::endl; } // final status if (is_root) std::cout << "# Final squared error after " << counter << " iterations: " << error << std::endl; ////////////////////////////////////////////////////////////////////////// // GATHER ////////////////////////////////////////////////////////////////////////// MPI::COMM_WORLD.Gatherv( ying.data(), local_height*local_width,MPI::DOUBLE, image.data(), counts, displs, tile_t, 0); ////////////////////////////////////////////////////////////////////////// // CHECK ////////////////////////////////////////////////////////////////////////// if (is_root) { std::string filename = random_string(8)+".bmp"; dump_bitmap(image.data(), height, width, "www/"+filename); std::cout << "# See http://iaimz105.informatik.uni-mainz.de:8000/" << filename << "\nParallel programming is " << (counter == 8353 ? "fun!" : "error-prone!") << std::endl; } MPI::Finalize(); }

Start time:

Do 10 Okt 2019 10:15:00

End time:

Di 11 Feb 2020 10:15:00

General test timeout:

10.0 seconds

Tests

Parallel programming is fun!

Parallel programming is fun!