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Subject: Re: [OMPI devel] Duplicated modex issue.
From: Ralph Castain (rhc_at_[hidden])
Date: 2012-12-20 11:57:13


On Dec 20, 2012, at 8:29 AM, Victor Kocheganov <victor.kocheganov_at_[hidden]> wrote:

> Thanks for fast answer, Ralph.
>
> In my example I use different collective objects. I mean in every mentioned block I call coll = OBJ_NEW(orte_grpcomm_collective_t);
> and OBJ_RELEASE(coll); , so all the grpcomm operations use unique collective object.

How are the procs getting the collective id for those new calls? They all have to match

>
>
> On Thu, Dec 20, 2012 at 7:48 PM, Ralph Castain <rhc_at_[hidden]> wrote:
> Absolutely it will hang as the collective object passed into any grpcomm operation (modex or barrier) is only allowed to be used once - any attempt to reuse it will fail.
>
>
> On Dec 20, 2012, at 6:57 AM, Victor Kocheganov <victor.kocheganov_at_[hidden]> wrote:
>
>> Hi.
>>
>> I have an issue with understanding ompi_mpi_init() logic. Could you please tell me if you have any guesses about following behavior.
>>
>> I wonder if I understand ringh, there is a block in ompi_mpi_init() function for exchanging procs information between processes (denote this block 'modex'):
>> coll = OBJ_NEW(orte_grpcomm_collective_t);
>> coll->id = orte_process_info.peer_modex;
>> if (ORTE_SUCCESS != (ret = orte_grpcomm.modex(coll))) {
>> error = "orte_grpcomm_modex failed";
>> goto error;
>> }
>> /* wait for modex to complete - this may be moved anywhere in mpi_init
>> * so long as it occurs prior to calling a function that needs
>> * the modex info!
>> */
>> while (coll->active) {
>> opal_progress(); /* block in progress pending events */
>> }
>> OBJ_RELEASE(coll);
>> and several instructions after this there is a block for processes synchronization (denote this block 'barrier'):
>> coll = OBJ_NEW(orte_grpcomm_collective_t);
>> coll->id = orte_process_info.peer_init_barrier;
>> if (ORTE_SUCCESS != (ret = orte_grpcomm.barrier(coll))) {
>> error = "orte_grpcomm_barrier failed";
>> goto error;
>> }
>> /* wait for barrier to complete */
>> while (coll->active) {
>> opal_progress(); /* block in progress pending events */
>> }
>> OBJ_RELEASE(coll);
>> So, initially ompi_mpi_init() has following structure:
>> ...
>> 'modex' block;
>> ...
>> 'barrier' block;
>> ...
>> I made several experiments with this code and the following one is of interest: if I add sequence of two additional blocks, 'barrier' and 'modex', right after 'modex' block, then ompi_mpi_init() hangs in opal_progress() of the last 'modex' block.
>> ...
>> 'modex' block;
>> 'barrier' block;
>> 'modex' block; <- hangs
>> ...
>> 'barrier' block;
>> ...
>> Thanks,
>> Victor Kocheganov.
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
>
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