Tpetra::Distributor: Don't fill indicesFrom_
Created by: mhoemmen
@trilinos/tpetra @jjellio @kddevin @vbrunini @crtrott
Tpetra::Distributor
would always fill indicesFrom_
with 0, 1, ..., totalReceiveLength_-1
. This was not only a waste of time, it would unnecessarily make all reverse-mode communication take the slow path. (Reversing a Distributor swaps indicesTo_
and indicesFrom_
. A nonempty indicesTo_
tells Distributor to take the slow path. If indicesFrom_
is just 0, 1, ..., totalReceiveLength_-1
, then Distributor does not need to take the slow path.)
Note that Epetra_MpiDistributor
comments out the code that fills indices_from_
, and claims that doing so fixes reverse communication.
@vbrunini found that applying my patch for fixing this made Aria's post-solve communication of the solution vector of the ViewFactor system a lot faster on 2 GPUs.
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