Re: [Patch] Add two tests of hash function quality

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi Matt,
> This patch adds two very different tests to verify that we have a good
> hash function. This is a very large and well studied area, and in principle
> we could have many more tests of this sort, but a least these ones are
> a start.
>
> One test is very simple to describe: it hashes a set of strings to a set
> of buckets, and uses chi^2 to verify that the distribution is uniform.
> The other is slightly more complicated, but essentially it verifies that
> every bit of the input string affects every bit of the output hash code.
>   
I think the patch is almost ready to go in. Thanks. I have only a
concern, that these tests may take a little too much to run (*) and
timeout on simulators: can you imagine a sensible way to use one of
those DejaGnu directives like (we have already quite a few examples in
the testsuite):

    // { dg-options "-DMAX_ITERATIONS=5" { target simulator } }

Thanks again,
Paolo.

(*) In particular quality.cc, ~17 secs of real time on my rather new i7
machine. Should be easier to tweak, since doesn't use a statistical test...