CSE6230 HW#3

CSE6230

Haoming Jiang
GTID: 903324367

Program:

hw3.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <sys/time.h>
double get_walltime(void)
{
  struct timeval tp;
  gettimeofday(&tp, NULL);
  return (double) (tp.tv_sec + tp.tv_usec/1.e6);
}
int main()
{
    double x[10000][3];
    double y[10000][3];
    double dt = 1.e-4;
    double runtime = -get_walltime();
    unsigned int seed = omp_get_thread_num();
    // initialize x
    #pragma omp parallel for schedule(runtime)
    for(int i = 0; i < 10000; i++)
    {
        x[i][0] = 1.0 * rand_r(&seed) / RAND_MAX;
        x[i][1] = 1.0 * rand_r(&seed) / RAND_MAX;
        x[i][2] = 1.0 * rand_r(&seed) / RAND_MAX;
        y[i][0] = y[i][1] = y[i][2] = 0;
    }
    for(int iter = 0; iter < 10; iter++)
    {
        #pragma omp parallel for schedule(runtime)
        for(int i = 0; i < 10000; i++)
        {
            for(int j = 0; j < 500; j++)
            {
                y[i][0] += sqrt(2 * dt)* (2.0 * rand_r(&seed) / RAND_MAX - 1);
                y[i][1] += sqrt(2 * dt)* (2.0 * rand_r(&seed) / RAND_MAX - 1);
                y[i][2] += sqrt(2 * dt)* (2.0 * rand_r(&seed) / RAND_MAX - 1);
            }
        }
        double avgdist = 0;
        #pragma omp parallel for reduction(+:avgdist) schedule(runtime)
        for(int i = 0; i < 10000; i++)
        {
        avgdist += sqrt( y[i][0]*y[i][0] + y[i][1]*y[i][1] + y[i][2]*y[i][2]);
        }
        avgdist /= 10000;
        printf("Average Distance: %lf, Average Distance/sqrt(Time): %lf\n", avgdist, avgdist/sqrt((iter+1)*500*dt));
    }
    runtime += get_walltime();
    printf("runtime: %lf\n\n", runtime);
    return 0;
}

Makefile

CC = cc
CFLAGS = -g -O -Wall -fopenmp 
.PHONY:
    clean runhw3
runhw3: hw3.c
    $(CC) $(CFLAGS) -o hw3 hw3.c -lm
    for nt in `seq 1 8`; do \
        OMP_SCHEDULE="guided,20" OMP_NUM_THREADS=$$nt ./hw3 $N; \
    done
clean:
    $(RM) hw3

Graph of average distance moved from 0 to 5000 time steps

Table of the execution time for a few different loop scheduling options, and using an appropriate number of threads.