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Wrong Results from multiScan for large number of rows #42

Closed GoogleCodeExporter closed 8 years ago

GoogleCodeExporter commented 8 years ago 
What steps will reproduce the problem?
I've included a function that runs the CUDPP multiScan and checks it
against what I think should appear using the CPU. For me it fails with a
datasize of 50000 and 100 rows.

What is the expected output? What do you see instead?
I would expect the test to pass. If you use the cudppScan inside the For
loop instead the test passes.

What version of the product are you using? On what operating system?

Using CUDPP 1.1 on Vista 64-bit with Visual Studio 2008. I'm using CUDA
2.2. I won't have time to test it using 2.3 as I'm about to leave the
country so maybe someone can confirm that it's still a fault with 2.3.

Please provide any additional information below.

I believe the problem lies in the scan_cta.cu file. In the scanCTA
function, a syncthreads is called only in emulation mode for backwards
scans. I think this needs to get called for device mode as well. At least
that fixed the problem for me. It looks like there would be race conditions
for large numbers of threads.

Original issue reported on code.google.com by inthecro...@gmail.com on 29 Sep 2009 at 12:00

Attachments:

GoogleCodeExporter commented 8 years ago

Original comment by harr...@gmail.com on 19 Nov 2009 at 1:38

GoogleCodeExporter commented 8 years ago

Original comment by harr...@gmail.com on 19 Nov 2009 at 1:39

GoogleCodeExporter commented 8 years ago 
I cannot reproduce this issue using the attached code.  On my G84 laptop with 
CUDA 2.3 
I ran sumTest(100, 50000, 1) and it does not report failure.

inthecrossfire: if you are getting this, please provide more information.  
Note, your 
test did not have a main() function, so I had to add one.  All it does is 
execute 
sumTest(100, 50000, 1).

Original comment by harr...@gmail.com on 14 Dec 2009 at 7:32

GoogleCodeExporter commented 8 years ago

Original comment by harr...@gmail.com on 20 Jan 2010 at 8:25

GoogleCodeExporter commented 8 years ago 
I do apologise for taking so long to respond. Unfortunately I've no longer got 
access
to the computer that suffered that bug. Perhaps it was something specific to 
the set
up. I just tested the code on my laptop and I agree that there doesn't seem to 
be a
problem. So I guess there isn't much more that can be done.

Original comment by inthecro...@gmail.com on 21 Jan 2010 at 12:54

GoogleCodeExporter commented 8 years ago 
Thanks for responding, inthecrossfire.  Since we don't have a repro, I'm going 
to close 
this issue.  If you run into the problem again, please do report it!

Original comment by harr...@gmail.com on 21 Jan 2010 at 12:58