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Subject: Re: [boost] [random] recent changes causing failures in accumulators tests
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-05-27 01:24:44


On 05/26/2011 09:49 PM, Eric Niebler wrote:
> Many accumulators tests are now failing on both trunk and release. I
> have tracked it down to recent changes in Boost.Random. I don't know for
> how long this has been happening.
> The accumulators tests use the lagged_fibonacci607 random number
> generator. The tests work by sending a large amount of random data
> through various statistical accumulators and checking that the results
> are within a certain tolerance of what they would be if the data were
> actually random. In Boost 1.45 and previous versions, this worked. (I
> haven't tested 1.46.) Trunk and release are hosed, leading me to suspect
> that this random number generator is no longer producing sufficiently
> random data.
> I have verified this by replacing boost/random on trunk with the one
> from 1.45. With this change, the accumulators tests pass.
> Steven, this seems like a regression. Can you look into this?

I think the only thing I changed was the seeding algorithm.
The number of random bits was reduced from 53 to 48, but
that's all lagged_fibonacci607 ever claimed to provide.

Your limits may be too low. I switched extended_p_square.cpp
to use mt19937_64 and random_device with
generate_canonical<double, 53> and it still failed
with both. It's getting a bit late tonight. I'll
work through the math tomorrow.

In Christ,
Steven Watanabe

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