Re: [eigen] FLENS C++ expression template Library has excellent documentation

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On Sat, Apr 18, 2009 at 7:40 AM, Rohit Garg <rpg.314@xxxxxxxxx> wrote:
> On Sat, Apr 18, 2009 at 10:53 AM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
>> 2009/4/18 Rohit Garg <rpg.314@xxxxxxxxx>:
>>>> So, in which area does Intel MKL still have a long-term lead? I would
>>>> say parallelization. We haven't started that yet and it is probably a
>>>> very, very tough one. It's what I have in mind when I say that a
>>>> BLAS/LAPACK wrapper is still welcome.
>>> Why do you think parallelization is very difficult? Do you mean
>>> parallelization nfrastructure?  AFAICS, using openmp will be cool. Let
>>> compiler handle all the dirty buisness etc This is something I want to
>>> explore (time availability is of course important !) so I would like
>>> some heads up.
>> I'm very ignorant of these matters. If parallelization can be done in
>> a generic way, then yes I understand that it's just a matter of
>> OpenMP-ifying for loops. Although even so, there remain issues to
>> sort: what if the user application doesn't want Eigen to launch more
>> than N threads, because it is already launching a lot of threads of
>> its own? OpenMP 2 didnt seem to help much in that situation, maybe 3
>> is better.
> I was thinking of something like -DEIGEN_PARALLEL 4 (ie opt in
> parallelization) at compile time to launch that many threads at
> compile time. BLAS 1 should be trivial to parallelize and BLAS2
> shouldn't be too difficult either.

unfortunately no, the problem is that we need to be able to control
that per expression, and we ave to come up with a good API for
that.Since eigen is a pure template library we cannot have global
states for that.

actually we have already experimented wit openMP, have a look at the
file disabled/EvalOMP.h


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