Hi,
Thank you Andrew for this feature which will be valuable for me as well!
I am using the java version of glpk, and I am wondering if it has also been
tested with multi-threads. What do I have to change in the java or swig
files in order to be able to take this into account? For example, where do I
have to initialize the environment thread pointer?
Sylvain Fournier
Date: Thu, 15 Apr 2010 14:06:15 +0400
> From: Andrew Makhorin <m...@gnu.org>
> Subject: Re: [Help-glpk] Thread safety of GLPK
> To: "Hammond, Paul" <paul.hamm...@morganstanley.com>
> Cc: help-glpk@gnu.org
> Message-ID: <474395093.20100415140...@gnu.org>
> Content-Type: text/plain; charset="us-ascii"
>
> > Thanks for this. If you find your old code, do send it over, we
> > don't mind if it's not the standard release, if it works, we'll
> > consider using it.
>
> Please see the attachment.
>
> You need to replace file glpenv02.c with a reentrant version and then
> build the package as usual. Note that glpsol will not work, because it
> does not create the thread-specific data key used in the reentrant
> version of glpenv02.c. Mtsamp.c is an example program that works.
>
> Hope this helps.
>
> Andrew Makhorin
> -------------- next part --------------
> /* glpenv02.c (thread local storage) */
>
> /* (reserved for copyright notice) */
>
> #include <pthread.h>
> #include "glpenv.h"
>
> /* re-enterable POSIX version */
>
> pthread_key_t _glp_pth_key;
> /* must be initialized in the main program */
>
> void tls_set_ptr(void *ptr)
> { pthread_setspecific(_glp_pth_key, ptr);
> return;
> }
>
> void *tls_get_ptr(void)
> { void *ptr;
> ptr = pthread_getspecific(_glp_pth_key);
> return ptr;
> }
>
> /* eof */
> -------------- next part --------------
> /* mtsamp.c */
>
> /***********************************************************************
> * This is an example program which illustrates how to use GLPK API in
> * multi-threaded application on POSIX platform.
> *
> * To run this program use the following command:
> *
> * mtsamp.exe mps-file-1 mps-file-2 ... mps-file-n
> *
> * Each mps file specified in the command line is processed by separate
> * thread.
> ***********************************************************************/
>
> #include <pthread.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <glpk.h>
>
> void *solve_mps(void *arg)
> { char *fname = arg;
> glp_prob *P;
> P = glp_create_prob();
> if (glp_read_mps(P, GLP_MPS_FILE, NULL, fname) != 0)
> { fprintf(stderr, "Cannot read mps file `%s'\n", fname);
> return NULL;
> }
> glp_simplex(P, NULL);
> glp_delete_prob(P);
> glp_free_env();
> return NULL;
> }
>
> #define MAX_THREADS 20
>
> extern pthread_key_t _glp_pth_key;
>
> int main(int argc, char *argv[])
> { pthread_t h[1+MAX_THREADS];
> int t, ret;
> if (argc < 2)
> { fprintf(stderr, "At least one mps file must be specified\n");
> exit(EXIT_FAILURE);
> }
> if (argc-1 > MAX_THREADS)
> { fprintf(stderr, "Too many mps files\n");
> exit(EXIT_FAILURE);
> }
> ret = pthread_key_create(&_glp_pth_key, NULL);
> if (ret != 0)
> { fprintf(stderr, "Unable to create thread-specific key\n");
> exit(EXIT_FAILURE);
> }
> for (t = 1; t < argc; t++)
> { ret = pthread_create(&h[t], NULL, solve_mps, argv[t]);
> if (ret != 0)
> { fprintf(stderr, "Unable to create thread for `%s'\n",
> argv[t]);
> exit(EXIT_FAILURE);
> }
> }
> for (t = 1; t < argc; t++)
> { ret = pthread_join(h[t], NULL);
> if (ret != 0)
> { fprintf(stderr, "Waiting failure for thread %d\n", t);
> exit(EXIT_FAILURE);
> }
> }
> fprintf(stderr, "GLPK multi-threaded DLL seems to work\n");
> return 0;
> }
>
> /* eof */
>
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