Posted By: Drs (Fortran je muj kamarad) on 'CZprogram'
Title:     Re: posix threads *^*&%*$*
Date:      Mon Sep 24 12:21:50 2001

> Dik za kazde info, kdybyste nekdo zverejnili kratky programek, ktery chodi, 
> budu neskonale vzdecny.

Cau !
Drive jsem neco s pthready delal, takze jsem z jednoho programu vykuchal 
relevantni cast a hazim ji sem. Puvodne to byla cast kodu, ktery bezel na 
linuxovem clusteru a mezi nody komunikoval pomoci MPI, takze jsou tam jiste 
neobratnosti v syntaxi, ktere tam zustaly, kdyz jsem ted tohle MPI vyhazel. 
To je souveti :-))
Toz tady je:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <pthread.h>

double f(double x)
{
  double y;
  y=x + sin(x);
  return y;
}

double solution=0.0;         /* integral*/
double mya;                  /* beginning of my interval */
double myb;                  /* end of my interval */
double myd;                  /* step */
double d;                    /* length of interval*/

pthread_mutex_t mut;

void *slave()
{
  double x;
  double pomssol=0.0;
  for (x=mya; x<mya+d/2.0; x=x+myd) /*integration over the 2nd half of int. */
    {
      pomssol=pomssol+0.5*(f(x)+f(x+myd))*myd;
    }
  pthread_mutex_lock(&mut);         /* becouse changing global variable */
    solution=solution+pomssol;      /* returning result */
  pthread_mutex_unlock(&mut);
  return;
}

int main(int argc, char **argv)
{
  FILE *outp;
  double PI=3.141592654;
  double a=0.0;                /* left border */
  double b=PI;                 /* right border */
  double pomsol=0.0;
  double x;                    /* point in which I compute the value */
  pthread_t thread;

  
  d=(b-a);
  myd=1.0e-7;
                               /* and sends it to all processes */
  mya=a;                       /* compute borders of my interval */ 
  myb=b;

  pthread_mutex_init(&mut,NULL);

  if (pthread_create(&thread,NULL,slave,NULL) != 0) 
    perror("Pthread create failed !!!");

  for (x=mya+d/2.0; x<myb; x=x+myd) /* comp. of integral over part of (a,b) */
    {
      pomsol=pomsol + 0.5*(f(x)+f(x+myd))*myd;
    }
  
  pthread_mutex_lock(&mut);          /* slave may write now too */
    solution=solution+pomsol;    /* total result of this node */
  pthread_mutex_unlock(&mut);

  if (pthread_join(thread,NULL) != 0)
    perror("Pthread join failed !!!");

  if ((outp = fopen("outp","w")) == NULL)
    { printf("Error open file !!!"); exit; };
  fprintf(outp,"Integral of the function from a to b is %f.n",solution);
  printf("Integral of the function from a to b is %f.n",solution);
  fclose(outp);

}

Ted jsem to zkousel prekladat na Linuxu RH 6.2 CZ, v pohode beha a funguje. 
Prekladal jsem to bezne gcc -O -lpthread -o pthr pthready.c
Treba to pomuze.

Tak a ted bud neskonale vdecny :-)

 
                                          DrS
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To jen aby rec nestala ...