On Thu, 22 Mar 2012, Shamis, Pavel wrote:
What: Change coll tuned default to pairwise exchange
Why: The linear algorithm does not scale to any reasonable number of PEs
When: Timeout in 2 days (Fri)
Is there any reason the default should not be changed?
Nathan,
I can see why people think the linear algorithm is bad. However I think it
depends on the application communication pattern in the alltoallv. Do you have
any numbers to back your claim?
George,
In addition the above list of dependencies it also depends on network
technology. The linear algorithm does not play well with IB.
Nor does it play well with Gemini. I will get some hard numbers early next week
on both our XE6 and one of our infiniband clusters.
-Nathan
