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From Martin Sebor <se...@roguewave.com>
Subject Re: STDCXX-536
Date Sun, 09 Mar 2008 23:41:06 GMT
Eric Lemings wrote:
> FWIW, I was just reading the description for Jira issue STDCXX-536 and
> the associated comments.
>  
> I believe this is basically what Travis has already stated in a round-
> about manner but it seems to me that if a test is timing out, there are
> two possibilities: 1. the test is caught in an infinite loop, or 2.)
> the test requires too much time to completely execute.  In either case,
> the test needs to be rewritten to fix the infinite loop or to break
> the test into smaller tests that can completely execute in a reasonably
> short amount of time -- a couple of minutes at most on the slowest
> supported platforms.

Right, that's the conclusion we came to for the tests that can be
broken up. The downside of doing this is code duplication (either
source or object) between the small tests that share the same
scaffolding, which will increase compilation and/or link times,
and, of course, run times. With a large enough of number of these
little tests the consequences could be actually worse than the
status quo.

The problem with most of our thread safety tests is that they are
written to do the sane fixed number of operations in parallel, and
this number takes a different amount of time depending on factors
such as the scheduler's time slice and the system load. Ideally,
the tests would take these parameters into consideration and run
for sufficiently long (but no longer) to exercise the functionality
with some desired percentage of parallelism/contention. To do that,
the tests would need to be able to time out.

> 
> And aren't multithreaded programs (or tests) supposed to perform faster
> -- not slower -- than their single-threaded counterparts?  :)

Only if they are written to avoid contention, which is the exact
opposite of what our thread safety tests are designed to do.

Martin

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