Re: Question about Threads

AgentM,

The treads are joined back together by the master. I did try to debug, but
have to say I hard a hard time with it. I have tried to debug, but didn't
get very far. Debugging Threads is not my forte. :(


Here is the code from :
/src/backend/optimizer/geqo/geqo_main.c
       for (i=0;i<thread_count;i++)       {               geqo_params[i].root = copyObject(root);
geqo_params[i].number_of_rels= number_of_rels;               geqo_params[i].initial_rels = copyObject(initial_rels); 
               geqo_params[i].root->base_rel_list =
listCopy(root->base_rel_list);               geqo_params[i].root->other_rel_list =
listCopy(root->other_rel_list);               geqo_params[i].root->join_rel_list =
listCopy(root->join_rel_list);               geqo_params[i].root->equi_key_list =
listCopy(root->equi_key_list);               geqo_params[i].root->query_pathkeys =
listCopy(root->query_pathkeys);
               geqo_params[i].myid = i;
               pthread_create(&thread_list[i],                       NULL,                       (void *(*)(void *))
geqo_single, (void *) 
&geqo_params[i]);       }
       // join all thread and get results       for (i=0;i<thread_count;i++)       {               elog(DEBUG1, "geqo:
tryingto join back thread %d", i);               pthread_join(thread_list[i],(void *) results[i]);               //
sortresults               if (best_so_far == -1)               {                       elog(DEBUG1, "geqo: thread %d is
firstthread we 
see", i);                       best_so_far = i;               }               else               {
 if 
(results[best_so_far]->cheapest_total_path->total_cost >
results[i]->cheapest_total_path->total_cost)                      {                               elog(DEBUG1, "geqo:
thread%d is better than 
thread %d ", i, best_so_far);                               best_so_far = i;
                       }               }


Leon


> -----Original Message-----
> From: AgentM [mailto:agentm@cmu.edu]
> Sent: Saturday, November 08, 2003 4:01 PM
> To: Leon Oosterwijk
> Subject: Re: [HACKERS] Question about Threads
>
> Are you using joined or detached pthreads? Have you tried debugging?
>
> On Saturday, Nov 8, 2003, at 22:47 Europe/Berlin, Leon
> Oosterwijk wrote:
>
> > All,
> >
> > I'm working on a school project that involves genetic
> algorithms. We
> > thought
> > it would be neat to parralelize the genetic algorithm in
> postgresql's
> > query
> > optimiser. We used pthreads and are able to spawn threads
> to deal with
> > the
> > query optimization, however on exit of the thread the
> postmaster blows
> > up.
> > Before we get into details is there any obvious reason postgres
> > doesn't like
> > to deal with threads?
> >
> > Thank you.
> >
> > Leon
> ¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬
> AgentM
> agentm@webopticon.com
> ¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬
>