91 lines
2.1 KiB
C
91 lines
2.1 KiB
C
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//
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// Written for Computer Networks and Systems lab classes
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// AUTHOR : Sergiusz Warga
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <time.h>
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#include <unistd.h>
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#define N_OF_ELEMENTS 1e6
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#define N_OF_CHILDREN 10
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#define SPAN (int)(N_OF_ELEMENTS/N_OF_CHILDREN)
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union floaty {
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float number;
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char bytes[sizeof(float)];
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};
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int child_task(float * array, int start) {
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union floaty sum;
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for (int i = start; i < start + SPAN; ++i ) {
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sum.number += array[i];
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}
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char filename[16];
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snprintf(filename, 16, "sum%d.txt", getpid());
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int file = open(filename, O_CREAT | O_WRONLY);
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write(file, sum.bytes, sizeof(sum));
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close(file);
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return 0;
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}
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float avg(float * array) {
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float sum = 0;
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for (int i = 0; i < N_OF_CHILDREN; ++i) {
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sum += array[i];
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}
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return sum/N_OF_ELEMENTS;
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}
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int main() {
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srandom(time(NULL));
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int status[N_OF_CHILDREN];
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float sums[N_OF_CHILDREN] = {0};
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int children_pids[N_OF_CHILDREN];
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float * array = malloc(N_OF_ELEMENTS * sizeof(float));
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for (int i = 0; i < N_OF_ELEMENTS; ++i) {
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array[i] = 2*(float)random()/RAND_MAX - 1; // Nasty
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}
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pid_t pid;
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for (int i = 0; i < N_OF_CHILDREN; ++i) {
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pid = fork();
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if (pid == -1) { // If something went wrong.
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perror("Fork: ");
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exit(EXIT_FAILURE);
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}
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if (pid == 0){ // If this is a child process.
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child_task(array, (int)(i*SPAN));
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exit(EXIT_SUCCESS);
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}
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children_pids[i] = pid;
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}
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for (int i = 0; i < N_OF_CHILDREN; ++i) {
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waitpid(children_pids[i], &status[i], 0);
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}
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char filename[16];
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union floaty sum;
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for (int i = 0; i < N_OF_CHILDREN; ++i) {
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sum.number = 0;
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snprintf(filename, 16, "sum%d.txt", children_pids[i]);
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int file = open(filename, O_RDONLY);
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read(file, sum.bytes, sizeof(sum));
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sums[i] = sum.number;
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close(file);
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}
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printf("avg = %f\n", avg(sums));
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return 0;
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}
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