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Commit 9b86401

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OpenMP version
1 parent 8a5659b commit 9b86401

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all:
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gcc -fopenmp argmax.c -lm -o argmax
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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#include <omp.h>
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void initialize(double *v, int N) {
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for (int i = 0; i < N; i++) {
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v[i] = (1 - pow(0.5 - (double)i/(double)N, 2)) * cos(2*M_PI*100* (i - 0.5)/N);
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}
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}
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void argmax_par(double *v, int N, double *m, int *idx_m) {
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*m = -1.;
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*idx_m = -1;
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#pragma omp parallel for shared(m, idx_m)
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for (int i = 0; i < N; i++) {
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#pragma omp critical
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if (v[i] > *m) {
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*m = v[i];
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*idx_m = i;
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}
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}
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}
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void argmax_seq(double *v, int N, double *m, int *idx_m) {
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*m = -1.;
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*idx_m = -1;
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for (int i = 0; i < N; i++) {
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if (v[i] > *m) {
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*m = v[i];
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*idx_m = i;
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}
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}
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}
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void argmax_recursive(double *v, int N, double *m, int *idx_m, int K) {
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if (N <= K) {
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argmax_seq(v, N, m, idx_m);
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return;
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}
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double ml, mr;
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int idx_ml, idx_mr;
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argmax_recursive(v, N/2, &ml, &idx_ml, K);
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argmax_recursive(v + N/2, N/2, &mr, &idx_mr, K);
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if (mr >= ml) {
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*m = mr;
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*idx_m = idx_mr + N/2;
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}
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else {
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*m = ml;
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*idx_m = idx_ml;
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}
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return;
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}
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void argmax_recursive_tasks(double *v, int N, double *m, int *idx_m, int K) {
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if (N <= K) {
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argmax_seq(v, N, m, idx_m);
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return;
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}
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double ml, mr;
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int idx_ml, idx_mr;
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#pragma omp task shared(ml, idx_ml)
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argmax_recursive_tasks(v, N/2, &ml, &idx_ml, K);
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#pragma omp task shared(mr, idx_mr)
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argmax_recursive_tasks(v + N/2, N/2, &mr, &idx_mr, K);
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#pragma omp taskwait
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if (mr >= ml) {
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*m = mr;
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*idx_m = idx_mr + N/2;
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}
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else {
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*m = ml;
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*idx_m = idx_ml;
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}
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return;
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}
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int main(int argc, char * argv[])
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{
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int N = 4096*4096;
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int K = (argc == 2) ? atoi(argv[1]) : 512;
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printf("Running argmax with K = %d\n", K);
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double *v = (double *)malloc(N*sizeof(double));
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double t_start, t_end;
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initialize(v, N);
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t_start = omp_get_wtime();
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double seq_m;
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int seq_idx_m;
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argmax_seq(v, N, &seq_m, &seq_idx_m);
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t_end = omp_get_wtime();
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printf("sequential for argmax: m = %5.2f, idx=%d, time=%fs\n", seq_m, seq_idx_m, t_end - t_start);
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t_start = omp_get_wtime();
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double par_m;
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int par_idx_m;
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argmax_par(v, N, &par_m, &par_idx_m);
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t_end = omp_get_wtime();
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printf("parallel for argmax: m = %5.2f, idx=%d, time=%fs\n", par_m, par_idx_m, t_end - t_start);
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t_start = omp_get_wtime();
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double rec_m;
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int rec_idx_m;
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argmax_recursive(v, N, &rec_m, &rec_idx_m, K);
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t_end = omp_get_wtime();
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printf("sequential recursive argmax: m = %5.2f, idx=%d, time=%fs\n", rec_m, rec_idx_m, t_end - t_start);
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t_start = omp_get_wtime();
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double task_m;
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int task_idx_m;
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#pragma omp parallel
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#pragma omp single
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argmax_recursive_tasks(v, N, &task_m, &task_idx_m, K);
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t_end = omp_get_wtime();
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printf("parallel recursive argmax: m = %5.2f, idx=%d, time=%fs\n", task_m, task_idx_m, t_end - t_start);
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free(v);
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return 0;
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}

‎OpenMP-Cholesky_Histograms_Argmax/Argmax/job.err

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gcc -fopenmp argmax.c -lm -o argmax
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Running argmax with K = 1
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sequential for argmax: m = 1.00, idx=8388608, time=0.018033s
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parallel for argmax: m = 1.00, idx=8388608, time=0.882080s
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sequential recursive argmax: m = 1.00, idx=8388608, time=0.171807s
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parallel recursive argmax: m = 1.00, idx=8388608, time=11.736740s
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Running argmax with K = 128
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sequential for argmax: m = 1.00, idx=8388608, time=0.018055s
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parallel for argmax: m = 1.00, idx=8388608, time=1.050966s
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sequential recursive argmax: m = 1.00, idx=8388608, time=0.027947s
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parallel recursive argmax: m = 1.00, idx=8388608, time=0.062163s
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Running argmax with K = 512
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sequential for argmax: m = 1.00, idx=8388608, time=0.018047s
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parallel for argmax: m = 1.00, idx=8388608, time=1.008227s
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sequential recursive argmax: m = 1.00, idx=8388608, time=0.026505s
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parallel recursive argmax: m = 1.00, idx=8388608, time=0.017224s
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Running argmax with K = 1024
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sequential for argmax: m = 1.00, idx=8388608, time=0.018049s
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parallel for argmax: m = 1.00, idx=8388608, time=1.061418s
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sequential recursive argmax: m = 1.00, idx=8388608, time=0.026117s
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parallel recursive argmax: m = 1.00, idx=8388608, time=0.013908s
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Running argmax with K = 2048
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sequential for argmax: m = 1.00, idx=8388608, time=0.018042s
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parallel for argmax: m = 1.00, idx=8388608, time=1.022062s
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sequential recursive argmax: m = 1.00, idx=8388608, time=0.026283s
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parallel recursive argmax: m = 1.00, idx=8388608, time=0.012478s
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#!/bin/bash
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#SBATCH --job-name=amax
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#SBATCH -p std
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#SBATCH --output=job.out
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#SBATCH --error=job.err
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#SBATCH --ntasks=1
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#SBATCH --cpus-per-task=8
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#SBATCH --time=00:00:10
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#lscpu
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export OMP_NUM_THREADS=4
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make
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./argmax 1
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./argmax 128
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./argmax 512
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./argmax 1024
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./argmax 2048
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Running argmax with K = 8192 using 8 threads
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sequential for argmax: m = 1.00, idx_m=8388608, time=0.017529s
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parallel for argmax: m = 1.00, idx_m=8388608, time=0.037767s
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sequential recursive argmax: m = 1.00, idx_m=8388608, time=0.020405s
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parallel recursive argmax: m = 1.00, idx_m=8388608, time=0.035056s
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CC=gcc
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CFLAGS=-O2 -fopenmp -march=native -lm -std=c99
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OBJ=cholesky
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all:
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$(CC) main.c $(OBJ).c -o $(OBJ) $(CFLAGS)
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clean:
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rm $(OBJ)
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