reduction / graal / kaveri / heterogeneous queueing ?

[Caspole, Eric]

Hi Jules,
I have been experimenting with IntStream reduces for a while now and mine works the same way, passing in the output array as you show here.The first version I have  is based on this algorithm in the BOLT library  - https://github.com/HSA-Libraries/Bolt/blob/master/include/bolt/cl/reduce_kernels.cl

The HSA runtime spec is not finalized yet. When it is we will have a better idea on the possibility of using the dynamic job queuing in Sumatra.
Regards,
Eric

________________________________________
From: graal-dev [graal-dev-bounces at openjdk.java.net] on behalf of Jules Gosnell [jules_gosnell at yahoo.com]
Sent: Tuesday, June 17, 2014 4:43 PM
To: graal-dev at openjdk.java.net
Subject: reduction / graal / kaveri / heterogeneous queueing ?

Guys,

I have been playing with a system of gpu based reduction that is
intended to work as follows:

e.g.

public void kernel(Object[] input, Object[] output, int i) {

   output[i] = foo(input[i*2], input[(i*2)+1];

}

foo is the reducing function and is expected to return the reduction of
two elements of the sequence being reduced.

kernel would be called with e.g.

  input=Object[2n], output=Object[n], i=n.


The idea is to go through a number of reduction steps, each one taking
an input of size 2x and producing an output of size x, which can then be
fed back into the same kernel as input for the following round. Odds and
ends can be picked up by the cpu and folded in at a suitable juncture -
repeat until output array is too small to reduce further on the gpu and
so finish up the reduction on the cpu....

Questions:

- does this sound sensible ?

- I've read about Kaveri h/w supporting heterogeneous (including
gpu->gpu) queueing. Is this available, or are there plans to surface it,
in clumatra/graal/okra ? I need this to sequence the steps of my
reduction efficiently.

- anything else that anyone feels is relevant :-)

looking forward to hearing from you,



Jules