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Enable OpenMP parallelization of row-major-sparse * dense products.

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I observed significant speed-up of the CG solver.
This commit is contained in:
Gael Guennebaud 2015-06-26 10:32:34 +02:00
parent 3f49cf4c90
commit 53b930887d
1 changed files with 32 additions and 7 deletions
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39
Eigen/src/SparseCore/SparseDenseProduct.h
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@ -30,23 +30,48 @@ struct sparse_time_dense_product_impl<SparseLhsType,DenseRhsType,DenseResType, t
typedef typename internal::remove_all<DenseRhsType>::type Rhs;
typedef typename internal::remove_all<DenseResType>::type Res;
typedef typename evaluator<Lhs>::InnerIterator LhsInnerIterator;
typedef typename evaluator<Lhs>::type LhsEval;
static void run(const SparseLhsType& lhs, const DenseRhsType& rhs, DenseResType& res, const typename Res::Scalar& alpha)
{
typename evaluator<Lhs>::type lhsEval(lhs);
LhsEval lhsEval(lhs);
Index n = lhs.outerSize();
#ifdef EIGEN_HAS_OPENMP
Eigen::initParallel();
Index threads = Eigen::nbThreads();
#endif
for(Index c=0; c<rhs.cols(); ++c)
{
Index n = lhs.outerSize();
for(Index j=0; j<n; ++j)
#ifdef EIGEN_HAS_OPENMP
// This 20000 threshold has been found experimentally on 2D and 3D Poisson problems.
// It basically represents the minimal amount of work to be done to be worth it.
if(threads>1 && lhs.nonZeros() > 20000)
{
typename Res::Scalar tmp(0);
for(LhsInnerIterator it(lhsEval,j); it ;++it)
tmp += it.value() * rhs.coeff(it.index(),c);
res.coeffRef(j,c) += alpha * tmp;
#pragma omp parallel for schedule(static) num_threads(threads)
for(Index i=0; i<n; ++i)
processRow(lhsEval,rhs,res,alpha,i,c);
}
else
#endif
{
for(Index i=0; i<n; ++i)
processRow(lhsEval,rhs,res,alpha,i,c);
}
}
}
static void processRow(const LhsEval& lhsEval, const DenseRhsType& rhs, DenseResType& res, const typename Res::Scalar& alpha, Index i, Index col)
{
typename Res::Scalar tmp(0);
for(LhsInnerIterator it(lhsEval,i); it ;++it)
tmp += it.value() * rhs.coeff(it.index(),col);
res.coeffRef(i,col) += alpha * tmp;
}
};
// FIXME: what is the purpose of the following specialization? Is it for the BlockedSparse format?
template<typename T1, typename T2/*, int _Options, typename _StrideType*/>
struct scalar_product_traits<T1, Ref<T2/*, _Options, _StrideType*/> >
{