Re: [boost] [boostcon12]Trouble with tuples very compiler dependent

Subject: Re: [boost] [boostcon12]Trouble with tuples very compiler dependent
From: Larry Evans (cppljevans_at_[hidden])
Date: 2012-11-19 11:38:10

On 11/19/12 10:19, Larry Evans wrote:
[snip]
> In contrast to the gcc4_8 compiler, with the clangxx compiler, the
> relative qualitative performance, is just the opposite.  IOW, the
> bcon12_horizontal implementation is faster than the bcon12_vertical
> implementation.  In fact, the rate of change of the performance
> difference accelerates as tree depth goes from 2 to 4.  The rate of
> change is so stark that it suggests, at least to me, there may be some
> bug in clang.  Of course that conclusion is based on almost no
> knowledge, on my part, of the clang implementation.
> 
> The tuple_benchmark_filt.py can be modified to filter out other parts
> of the benchmark run output, which is here:
> 
> http://svn.boost.org/svn/boost/sandbox/variadic_templates/sandbox/slim/test/tuple.benchmark.tree_builder.guage_time._.run.txt
> 
For example, when the filter criteria restricts
TUPLE_UNROLL_MAX to 10 (the same as TUPLE_SIZE),
then, with compiler=clangxx, bcon12_vertical
performs relatively better than bcon12_horizontal
as TREE_DEPTH increases, as shown in the attached.

-regards,
Larry