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Subject: Re: [OMPI devel] 1.3 PML default choice
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2009-01-13 15:14:35

The selection logic for the PML is very confusing and doesn't follow the
standard priority selection. The reasons for this are convoluted and not
worth discussing here. The bottom line, however, is that the OB1 PML will
be the default *UNLESS* the PSM (PathScale/Qlogic) MTL can be chosen, in
which case the CM PML is used by default.


On Tue, 13 Jan 2009, Bogdan Costescu wrote:

> On Tue, 13 Jan 2009, Tim Mattox wrote:
>> The cm PML does not use BTLs..., only MTLs, so
>> ... the BTL selection is ignored.
> OK, thanks for clarifying this bit, but...
>>> The README for 1.3b2 specifies that CM is now chosen if possible; in my
>>> trials, when I specify CM+BTL, it doesn't complain and works well.
>>> However either the default (no options) or OB1+BTL leads to the jumps
>>> mentioned above, which makes me believe that OB1+BTL is still chosen as
>>> default, contrary to what the README specifies.
> ... this bit is still unclear to me. Should OB1+BTL or CM+MTL be the default
> ? I have just tried using "mpi_show_mca_params" for both v1.3b2 and v1.3rc3
> and this tells me that:
> pml= (default value)
> pml_cm_priority=30 (default value)
> pml_ob1_priority=20 (default value)
> which, from what I know, should lead to CM being chosen as the default. Still
> for v1.3b2 OB1 seemed to be chosen; for v1.3rc3 I can't distinguish anymore
> from timings as they behave very similarly.