[Haskell-cafe] Possible bug in Criterion or Statistics package

Ryan Newton rrnewton at gmail.com
Mon Aug 13 17:43:35 CEST 2012

Terrible!  Quite sorry that this seems to be a bug in the monad-par library.

I'm copying some of the other monad-par authors and we hopefully can get to
the bottom of this.  If it's not possible to create a smaller reproducer,
is it possible to share the original test that triggers this problem?  In
the meantime, it's good that you can at least run without parallelism.


On Sun, Aug 12, 2012 at 11:20 AM, Aleksey Khudyakov <
alexey.skladnoy at gmail.com> wrote:

> On 10.08.2012 22:20, Till Berger wrote:
>>  So I am not sure if this is a bug in Criterion itself, the Statistics
>>>>> package or any dependency or if I am doing something obviously wrong. I
>>>>> would be grateful if someone could look into this as it is holding me
>>>>> back from using Criterion for benchmarking my code.
>>>>>  I would suspect Statistics.Resampling.**resample. From quick glance
>>>> criterion doesn't use any concurrent stuff. I'll try create smaller test
>>>> case
>>> It looks like I'm wrong. I obtained event log from crashing program
>>> and resample completed its work without problems. Crash occured later.
>>> Next
>>> suspect is bootstrapBCA itself. It uses monad-par to obtain
>>> parallelism[1].
>>> I tried to create smaller test case without any success.
>>> [1]
>>> https://github.com/bos/**statistics/blob/master/**Statistics/Resampling/
>>> **Bootstrap.hs#L84<https://github.com/bos/statistics/blob/master/Statistics/Resampling/Bootstrap.hs#L84>
>> Replacing "runPar $ parMap" with a simple "map" on that line seems to
>> fix the bug. At least I could not reproduce it anymore on several runs
>> with my original test case. So it seems to be a bug in the Par monad
>> package as this change shouldn't alter the program's behaviour, should it?
>>  Looks like this is the case. But reducing test case to reasonable size
> (e.g. removing most of criterion and statistics could be quite difficult
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