Re: [Help-gsl] is gsl_integration_workspace reusable?

[Denes Molnar]

Many thanks to everyone, it turns out this was a false alarm.

The whole issue arose because a collaborator could not independently 
reproduce some of my results. I just converted my own code to use a single 
workspace and all results stay the same. Also, I asked the colleague to 
take his fixed code and convert it back to use a single workspace, and the 
earlier discrepancies were not reproduced. This must have been some human 
error in the testing, possibly more changed in that code than the extra 
workspace allocations.

Anyway, explicit confirmation that the workspace is reusable was very 
useful. Not to mention that it is cleared by the gsl routines upon each 
call. It would probably be helpful to include this information in the 
manual (or have we missed it?).

Best regards, and thanks again,

Denes


Email from Rhys Ulerich on Dec 1, 2011 at 5:33pm:

> Hi Denes,
>
> > Unfortunately our 'test' code is 400-500 lines. We may be able to reduce it
> > in the coming weeks. Apart from all the bells and whistles, the original
> > code allocated a single workspace and then used that in a loop to compute
> > billions of integrals (calls to gsl_integration_qags()) with stochastic
> > parameters. The results were really strange (and wrong) until we changed the
> > code to allocate a workspace for every single integration.
>
> Any chance your test code is overwriting memory in places where it
> shouldn't?  If it trampled the gsl_integration_workspace I'd expect
> similar behavior which might be resolved by allocating new workspaces
> all the time.  What does valgrind say?  Do you see identical (or
> identically strange) results across different compiler versions or
> optimization levels?
>
> 400-500 lines isn't ideal but it'd be usable if you can reproduce the
> issue with O(2) iterations instead of billions.
>
> - Rhys