| 1 | /* |
| 2 | * SPDX-License-Identifier: MIT |
| 3 | * |
| 4 | * SPDX-FileCopyrightText: 2023 Olivier Dion <odion@efficios.com> |
| 5 | */ |
| 6 | |
| 7 | #include <assert.h> |
| 8 | #include <stdint.h> |
| 9 | #include <stdio.h> |
| 10 | #include <stdlib.h> |
| 11 | |
| 12 | #include <mpi.h> |
| 13 | |
| 14 | static uint64_t sum_of(uint64_t *values, size_t values_count) |
| 15 | { |
| 16 | size_t acc = 0; |
| 17 | for (size_t k=0; k<values_count; ++k) { |
| 18 | acc += values[k]; |
| 19 | } |
| 20 | return acc; |
| 21 | } |
| 22 | |
| 23 | static void usage() |
| 24 | { |
| 25 | fprintf(stderr, "Usage: test-mpi N\n"); |
| 26 | exit(EXIT_FAILURE); |
| 27 | } |
| 28 | |
| 29 | static uint64_t *allocate_values(size_t upto) |
| 30 | { |
| 31 | uint64_t *values = (uint64_t*)malloc(sizeof(uint64_t) * upto); |
| 32 | for (size_t k=0; k<upto; ++k) { |
| 33 | values[k] = k + 1; |
| 34 | } |
| 35 | return values; |
| 36 | } |
| 37 | |
| 38 | static void send_values(int target, uint64_t *values, |
| 39 | size_t values_count, |
| 40 | MPI_Request *request) |
| 41 | { |
| 42 | MPI_Isend(values, values_count, MPI_UINT64_T, |
| 43 | target, 0, MPI_COMM_WORLD, request); |
| 44 | } |
| 45 | |
| 46 | static void recv_answer(int target, uint64_t *value, |
| 47 | MPI_Request *request) |
| 48 | { |
| 49 | MPI_Irecv(value, 1, MPI_UINT64_T, |
| 50 | target, 0, MPI_COMM_WORLD, request); |
| 51 | } |
| 52 | |
| 53 | static void send_answer(uint64_t value) |
| 54 | { |
| 55 | MPI_Send(&value, 1, MPI_UINT64_T, |
| 56 | 0, 0, MPI_COMM_WORLD); |
| 57 | } |
| 58 | |
| 59 | static uint64_t *recv_values(size_t chunk_size) |
| 60 | { |
| 61 | uint64_t *values = (uint64_t*)malloc(sizeof(uint64_t) * chunk_size); |
| 62 | MPI_Recv(values, chunk_size, MPI_UINT64_T, |
| 63 | 0, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE); |
| 64 | return values; |
| 65 | } |
| 66 | |
| 67 | int main(int argc, char *argv[]) |
| 68 | { |
| 69 | int rank; |
| 70 | int size; |
| 71 | long long upto; |
| 72 | uint64_t *values; |
| 73 | |
| 74 | if (argc < 2) { |
| 75 | usage(); |
| 76 | } |
| 77 | |
| 78 | upto = atoll(argv[1]); |
| 79 | |
| 80 | if (upto <= 0) { |
| 81 | fprintf(stderr, "N must be greater than 0\n"); |
| 82 | exit(EXIT_FAILURE); |
| 83 | } |
| 84 | |
| 85 | MPI_Init(&argc, &argv); |
| 86 | |
| 87 | MPI_Comm_set_errhandler(MPI_COMM_WORLD, |
| 88 | MPI_ERRORS_RETURN); |
| 89 | |
| 90 | MPI_Comm_rank(MPI_COMM_WORLD, &rank); |
| 91 | MPI_Comm_size(MPI_COMM_WORLD, &size); |
| 92 | |
| 93 | size_t chunk_size; |
| 94 | size_t rest; |
| 95 | uint64_t total; |
| 96 | |
| 97 | if (size > 1) { |
| 98 | chunk_size = upto / (size - 1); |
| 99 | rest = upto % (size - 1); |
| 100 | } else { |
| 101 | chunk_size = 0; |
| 102 | rest = upto; |
| 103 | } |
| 104 | |
| 105 | if (rank == 0) { |
| 106 | uint64_t sums[size]; |
| 107 | MPI_Request requests[size - 1]; |
| 108 | |
| 109 | values = allocate_values(upto); |
| 110 | |
| 111 | for (int k=1; k<size; ++k) { |
| 112 | send_values(k, |
| 113 | values + (chunk_size * (k - 1)), |
| 114 | chunk_size, |
| 115 | &requests[k-1]); |
| 116 | } |
| 117 | |
| 118 | sums[0] = sum_of(values + chunk_size * (size - 1), |
| 119 | rest); |
| 120 | |
| 121 | MPI_Waitall(size - 1, requests, MPI_STATUS_IGNORE); |
| 122 | |
| 123 | for (int k=1; k<size; ++k) { |
| 124 | recv_answer(k, &sums[k], &requests[k-1]); |
| 125 | } |
| 126 | |
| 127 | MPI_Waitall(size - 1, requests, MPI_STATUS_IGNORE); |
| 128 | |
| 129 | total = sum_of(sums, size); |
| 130 | } else { |
| 131 | send_answer(sum_of(recv_values(chunk_size), |
| 132 | chunk_size)); |
| 133 | } |
| 134 | |
| 135 | MPI_Finalize(); |
| 136 | |
| 137 | if (rank == 0){ |
| 138 | assert(total == |
| 139 | (((uint64_t)upto * ((uint64_t)upto + 1U)) >> 1U)); |
| 140 | } |
| 141 | |
| 142 | return 0; |
| 143 | } |