AnsweredAssumed Answered

Tahiti 2048 threads max?

Question asked by corry on Feb 24, 2012
Latest reply on Feb 27, 2012 by corry

Ok, so after todays earlier glitch (still not sure if it was the computer or the brain), I'm trying to be extremily careful in testing...however, I can't seem to get Tahiti to run more than 2048 threads.  Its likely there is more I don't understand...

I'm running a program block of 64,1,1 and a grid size of 32,8,1.  Yet, a simple program that looks something like

il_cs_2_0

dcl_num_threads_per_group 64

dcl_uav_id(0)

dcl_literal l0, 0x00000010, 0, 0, 0

imul r1000.x, vAbsTidFlat.x, l0.x

uav_raw_store_id(0) mem, r1000.x, vAbsTidFlat

endmain

end

 

gets me results showing

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

01 00 00 00 01 00 00 00 01 00 00 00 01 00 00 00

.

.

.

ff 7f 00 00 ff 7f 00 00 ff 7f 00 00 ff 7f 00 00

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

.

.

.

I made sure to set my uav size to something ludicrous like 1MB just to make sure it was going to read all of it.  No matter what I do though, I get 0-2047. 

I assume I'm doing something wrong, but given that simple of a test case, I don't know what it could be.  I do know that setting it to just run 2048 works, but is abysmaly slow.  Running 64,1,1 32,8 gets me some insane performance, but incorrect results.  Yeah, I'm at a loss here.

Help?

Outcomes