Folks,
one drawback of retrieving time with rdtsc is that this value is core
specific :
if a task is not bound to a core, then the value returned by MPI_Wtime()
might go backward.
if i run the following program with
taskset -c 1 ./time
and then move it accross between cores
(taskset -cp 0 ; tas
AFAIK, Linux synchronizes all CPU timers on boot. The skew is normally no
more than 50-100 CPU cycles.
The reasons why you can observe larger differences are:
1) Main. The CPUs do not have "constant TSC" feature . Without this feature
timer frequency changes across different power states of CP
Gilles' concern is correct: we should never return timer values that go
backwards.
Perhaps the TSC-based WTIME should only be used in a process that is bound to a
single core...?
An MCA param can be used to force the switch between gettimeofday() and TSC, if
someone really wants to take their
On Nov 26, 2014, at 2:08 PM, Nick Papior Andersen wrote:
> Here is my commit-msg:
> "
> We can now split communicators based on hwloc full capabilities up to BOARD.
> I.e.:
> HWTHREAD,CORE,L1CACHE,L2CACHE,L3CACHE,SOCKET,NUMA,NODE,BOARD
> where NODE is the same as SHARED.
> "
>
> Maybe what I did
Sure, I will make the changes and commit to make them OMPI specific.
I will post forward my problems on the devel list.
I will keep you posted. :)
2014-11-27 13:58 GMT+01:00 Jeff Squyres (jsquyres) :
> On Nov 26, 2014, at 2:08 PM, Nick Papior Andersen
> wrote:
>
> > Here is my commit-msg:
> >
Many thanks!
Note that it's a holiday week here in the US -- I'm only on for a short time
here this morning; I'll likely disappear again shortly until next week. :-)
On Nov 27, 2014, at 8:12 AM, Nick Papior Andersen wrote:
> Sure, I will make the changes and commit to make them OMPI specifi
No worries :)
2014-11-27 14:20 GMT+01:00 Jeff Squyres (jsquyres) :
> Many thanks!
>
> Note that it's a holiday week here in the US -- I'm only on for a short
> time here this morning; I'll likely disappear again shortly until next
> week. :-)
>
>
>
> On Nov 27, 2014, at 8:12 AM, Nick Papior Ande
Why can't I set parameters like this (not the only one) with 1.8.3?
WARNING: A user-supplied value attempted to override the default-only MCA
variable named "btl_sm_use_knem".
It could be because configure did not find the knem headers and hence knem is
not supported and hence this mca parameter is read-only
My 0.2 us$ ...
Dave Love さんのメール:
>Why can't I set parameters like this (not the only one) with 1.8.3?
>
> WARNING: A user-supplied value attempted to override th
Hi Dave, Gilles, list
There is a problem with knem in OMPI 1.8.3.
A fix is supposed to come on OMPI 1.8.4.
Please, see this long thread:
http://www.open-mpi.org/community/lists/users/2014/10/25511.php
Note also, as documented in the thread,
that in the OMPI 1.8 series "vader" replaces "sm" as th
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