cancel
Showing results for 
Search instead for 
Did you mean: 

Archives Discussions

dukeleto
Adept I

segfault at clBuildProgram

Hi,

after modifying a number of variable declarations from

double to single precision in a (working) .cl file, I now have

a systematic segmentation fault at the clBuildProgram call.

It does not seem to be a syntax error, since the code compiles

properly with another vendor's environment.

Any suggestions on how best to approach a problem like this?

Thanks,

Olivier

0 Likes
8 Replies
titanius
Adept II

Re: segfault at clBuildProgram

maybe a long shot but you try finding if its due to some formatting errors, that cause the compiler to fail, by building the kernel in CodeXL analyze mode?

wolf0
Adept I

Re: segfault at clBuildProgram

That's happened to me before - I had to modify a loop into an two loops and an if statement to make the compiler quit crashing on me.

dukeleto
Adept I

Re: segfault at clBuildProgram

Thanks for the suggestion. Unfortunately, trying to analyze the kernel file with CodeXL (latest version 1.5-5364, with latest catalyst driver) also results in a segfault. It is rather frustrating! Looks like I'm going to have to remove the kernels one by one from the .cl file, to see when the segfaults disappear ...

0 Likes
dukeleto
Adept I

Re: segfault at clBuildProgram

Thanks for the heads up, Wolf; did you have an "automated" or at least tolerable way of identifying which kernel the problem was in?

0 Likes
wolf0
Adept I

Re: segfault at clBuildProgram

Actually, no - I was optimizing, making small changes and checking the speed, so I immediately knew which change did it.

0 Likes
dukeleto
Adept I

Re: segfault at clBuildProgram

In case anyone from the compiler team is interested, I think I have tracked down the main cause of my segfaults :

implicit type casting from single to double or double to single.

When I remove all of them, the code compiles, with one or two type casts, still no problem, but when I leave a number

of implicit type casts, the segfault at cl compilation occurs.

While I fully understand that implicit type casting is really not something I should be doing from a numerical correctness point of view,

it would be nice if the compiler were able to warn of the locations where they are being performed (currently, it says nothing at all)

rather than segfaulting!

Olivier

0 Likes
dipak
Staff
Staff

Re: segfault at clBuildProgram

It's hard to comment what may be the actual reason behind this segfault. However, I agree with you that one cannot expect a segfault against some implicit type casting. If that is the case, it would be really helpful for us if you share a testcase that manifests the issue. Your input can help us to improve the performance of compiler/driver in future.

Regards,

0 Likes
dukeleto
Adept I

Re: segfault at clBuildProgram

Thanks for the comment.

I will attempt to whittle down my (long: 15000+ lines of kernel) .cl to something reasonably short

which exhibits the same behaviour, and if successful, will send it to you.

Regards,

Olivier

0 Likes