Re: [Help-glpk] Thread-safety

[François Galea]

Andrew Makhorin a écrit :
> > I would like to know if GLPK is thread-safe or not. It seems it's using
> > a global "pointer" (in the glplib1a.c file) variable quite intensively, 
> > thus I imagine GLPK is not thread-safe. I have not investigated very 
> > much in the code of GLPK, so maybe I have missed a crucial point about 
> > this subject.
>
> All glpk routines are reenterable except two platform-dependent routines
> lib_set_ptr and lib_get_ptr which are placed in file glplib1a.c. A generic
> version of these routines uses a static storage to store the pointer (to
> glpk environmental block). There is a version of these routines for
> 32-bit Windows (sysdep/w32/glplib1a.c) which uses TLS, so that version
> is reenterable; however, for GNU/Linux such a version is not implemented.
>
> Reentarabiliy differs from thread-safety in the sense that though
> reenterable routines can be used in a multi-thread program, different
> threads cannot share the same program object (LPX), because the glpk
> routines have no synchronization features.

What I need is indeed reentrability : what I want to do is solve 
different subproblems of the same problem in parallel, so each LPX is 
local to one thread only.

I think it should be possible to implement an GNU/Linux equivalent for 
your TLS-based routines, using the pthread_setspecific family of 
routines of the POSIX threads library. I can have a look at it, if you like.

regards,

François


--
François Galea
Equipe OPALE - Laboratoire PRiSM
Université de Versailles-Saint Quentin en Yvelines
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