Thank you, Gilles and Jeff. This makes a lot of sense now.
And, Jeff, I thnk the paper you mentioned is this
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5184825&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5184825
?
Thank you,
Slaiya
On Mon, May 30, 2016 at 9:
> So, you mean that it guarantees the value received after the bcast call is
> consistent with value sent from root, but it doesn't have to wait till all
> the ranks have received it?
>
> this is what i believe, double checking the standard might not hurt though
> ...
>
No function has barrier sem
On 5/30/2016 11:09 PM, Saliya Ekanayake wrote:
So, you mean that it guarantees the value received after the bcast
call is consistent with value sent from root, but it doesn't have to
wait till all the ranks have received it?
this is what i believe, double checking the standard might not hurt
So, you mean that it guarantees the value received after the bcast call is
consistent with value sent from root, but it doesn't have to wait till all
the ranks have received it?
Still, in this benchmark shouldn't the max time for bcast be equal to that
of barrier?
On Mon, May 30, 2016 at 9:33 AM,
These are very different algorithms, so performance might differ (greatly)
for example, MPI_Bcast on root rank can MPI_Send() and return, if the
message is short, this is likely an eager send which is very fast.
that means MPI_Bcast() returns before all ranks received the data, or even
entered MPI
e times?
>
> Thanks,
>
> Matthieu
>
> --
> *From:* users [users-boun...@open-mpi.org] on behalf of Saliya Ekanayake [
> esal...@gmail.com]
> *Sent:* Monday, May 30, 2016 7:53 AM
> *To:* Open MPI Users
> *Subject:* [OMPI users] Broadcast faster
Hi,
How are you measuring these times?
Thanks,
Matthieu
From: users [users-boun...@open-mpi.org] on behalf of Saliya Ekanayake
[esal...@gmail.com]
Sent: Monday, May 30, 2016 7:53 AM
To: Open MPI Users
Subject: [OMPI users] Broadcast faster than barrier
Hi
Hi,
I ran Ohio micro benchmarks for openmpi and noticed broadcast with smaller
number of bytes is faster than a barrier - 2us vs 120us.
I'm trying to understand how this could happen?
Thank you
Saliya
