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mtl4-with-viennacl.cpp

This tutorial shows how data can be directly transferred from the MTL4 Library to ViennaCL objects using the built-in convenience wrappers.

The first step is to include the necessary headers and activate the MTL4 convenience functions in ViennaCL:

// System headers
#include <iostream>
// MTL4 headers
#include <boost/numeric/mtl/mtl.hpp>
#include <boost/numeric/itl/itl.hpp>
// Must be set prior to any ViennaCL includes if you want to use ViennaCL algorithms on MTL4 objects
#define VIENNACL_WITH_MTL4 1
// ViennaCL headers
#include "viennacl/vector.hpp"
#include "viennacl/matrix.hpp"
#include "viennacl/compressed_matrix.hpp"
#include "viennacl/linalg/ilu.hpp"
#include "viennacl/linalg/cg.hpp"
#include "viennacl/linalg/bicgstab.hpp"
#include "viennacl/linalg/gmres.hpp"
// Some helper functions for this tutorial:
#include "vector-io.hpp"

The following function contains the main code for this tutorial. It consists of the following steps:

- Creates MTL4 matrices and vectors
- Initializes them with data
- Create ViennaCL objects
- Copy them over to the respective ViennaCL objects
- Compute matrix-vector products in both MTL4 and ViennaCL and compare results.

template<typename ScalarType>
void run_tutorial()
{
typedef mtl::dense2D<ScalarType> MTL4DenseMatrix;
typedef mtl::compressed2D<ScalarType> MTL4SparseMatrix;

Create and fill dense matrices from the MTL4 library:

mtl::dense2D<ScalarType> mtl4_densemat(5, 5);
mtl::dense2D<ScalarType> mtl4_densemat2(5, 5);
mtl4_densemat(0,0) = 2.0; mtl4_densemat(0,1) = -1.0;
mtl4_densemat(1,0) = -1.0; mtl4_densemat(1,1) = 2.0; mtl4_densemat(1,2) = -1.0;
mtl4_densemat(2,1) = -1.0; mtl4_densemat(2,2) = -1.0; mtl4_densemat(2,3) = -1.0;
mtl4_densemat(3,2) = -1.0; mtl4_densemat(3,3) = 2.0; mtl4_densemat(3,4) = -1.0;
mtl4_densemat(4,4) = -1.0; mtl4_densemat(4,4) = -1.0;

Create and fill sparse matrices from the MTL4 library:

MTL4SparseMatrix mtl4_sparsemat;
set_to_zero(mtl4_sparsemat);
mtl4_sparsemat.change_dim(5, 5);
MTL4SparseMatrix mtl4_sparsemat2;
set_to_zero(mtl4_sparsemat2);
mtl4_sparsemat2.change_dim(5, 5);
{
mtl::matrix::inserter< MTL4SparseMatrix > ins(mtl4_sparsemat);
typedef typename mtl::Collection<MTL4SparseMatrix>::value_type ValueType;
ins(0,0) << ValueType(2.0); ins(0,1) << ValueType(-1.0);
ins(1,1) << ValueType(2.0); ins(1,2) << ValueType(-1.0);
ins(2,2) << ValueType(-1.0); ins(2,3) << ValueType(-1.0);
ins(3,3) << ValueType(2.0); ins(3,4) << ValueType(-1.0);
ins(4,4) << ValueType(-1.0);
}

Create and fill a few vectors from the MTL4 library:

mtl::dense_vector<ScalarType> mtl4_rhs(5, 0.0);
mtl::dense_vector<ScalarType> mtl4_result(5, 0.0);
mtl::dense_vector<ScalarType> mtl4_temp(5, 0.0);
mtl4_rhs(0) = 10.0;
mtl4_rhs(1) = 11.0;
mtl4_rhs(2) = 12.0;
mtl4_rhs(3) = 13.0;
mtl4_rhs(4) = 14.0;

Create the corresponding ViennaCL objects:

viennacl::vector<ScalarType> vcl_rhs(5);
viennacl::vector<ScalarType> vcl_result(5);
viennacl::matrix<ScalarType> vcl_densemat(5, 5);
viennacl::compressed_matrix<ScalarType> vcl_sparsemat(5, 5);

Directly copy the MTL4 objects to ViennaCL objects

viennacl::copy(&(mtl4_rhs[0]), &(mtl4_rhs[0]) + 5, vcl_rhs.begin()); //method 1: via iterator interface (cf. std::copy())
viennacl::copy(mtl4_rhs, vcl_rhs); //method 2: via built-in wrappers (convenience layer)
viennacl::copy(mtl4_densemat, vcl_densemat);
viennacl::copy(mtl4_sparsemat, vcl_sparsemat);
// For completeness: Copy matrices from ViennaCL back to Eigen:
viennacl::copy(vcl_densemat, mtl4_densemat2);
viennacl::copy(vcl_sparsemat, mtl4_sparsemat2);

Run dense matrix-vector products and compare results:

mtl4_result = mtl4_densemat * mtl4_rhs;
vcl_result = viennacl::linalg::prod(vcl_densemat, vcl_rhs);
viennacl::copy(vcl_result, mtl4_temp);
mtl4_result -= mtl4_temp;
std::cout << "Difference for dense matrix-vector product: " << mtl::two_norm(mtl4_result) << std::endl;
mtl4_result = mtl4_densemat2 * mtl4_rhs - mtl4_temp;
std::cout << "Difference for dense matrix-vector product (MTL4->ViennaCL->MTL4): "
<< mtl::two_norm(mtl4_result) << std::endl;

Run sparse matrix-vector products and compare results:

mtl4_result = mtl4_sparsemat * mtl4_rhs;
vcl_result = viennacl::linalg::prod(vcl_sparsemat, vcl_rhs);
viennacl::copy(vcl_result, mtl4_temp);
mtl4_result -= mtl4_temp;
std::cout << "Difference for sparse matrix-vector product: " << mtl::two_norm(mtl4_result) << std::endl;
mtl4_result = mtl4_sparsemat2 * mtl4_rhs - mtl4_temp;
std::cout << "Difference for sparse matrix-vector product (MTL4->ViennaCL->MTL4): "
<< mtl::two_norm(mtl4_result) << std::endl;
}

In the main() routine we only call the worker function defined above with both single and double precision arithmetic.

int main(int, char *[])
{
std::cout << "----------------------------------------------" << std::endl;
std::cout << "## Single precision" << std::endl;
std::cout << "----------------------------------------------" << std::endl;
run_tutorial<float>();
#ifdef VIENNACL_HAVE_OPENCL
if ( viennacl::ocl::current_device().double_support() )
#endif
{
std::cout << "----------------------------------------------" << std::endl;
std::cout << "## Double precision" << std::endl;
std::cout << "----------------------------------------------" << std::endl;
run_tutorial<double>();
}

That's it. Print a success message and exit.

std::cout << std::endl;
std::cout << "!!!! TUTORIAL COMPLETED SUCCESSFULLY !!!!" << std::endl;
std::cout << std::endl;
}

## Full Example Code

/* =========================================================================
Copyright (c) 2010-2016, Institute for Microelectronics,
Institute for Analysis and Scientific Computing,
TU Wien.
Portions of this software are copyright by UChicago Argonne, LLC.
-----------------
ViennaCL - The Vienna Computing Library
-----------------
Project Head: Karl Rupp rupp@iue.tuwien.ac.at
(A list of authors and contributors can be found in the PDF manual)
License: MIT (X11), see file LICENSE in the base directory
============================================================================= */
// System headers
#include <iostream>
// MTL4 headers
#include <boost/numeric/mtl/mtl.hpp>
#include <boost/numeric/itl/itl.hpp>
// Must be set prior to any ViennaCL includes if you want to use ViennaCL algorithms on MTL4 objects
#define VIENNACL_WITH_MTL4 1
// ViennaCL headers
#include "viennacl/vector.hpp"
#include "viennacl/matrix.hpp"
#include "viennacl/compressed_matrix.hpp"
#include "viennacl/linalg/ilu.hpp"
#include "viennacl/linalg/cg.hpp"
#include "viennacl/linalg/bicgstab.hpp"
#include "viennacl/linalg/gmres.hpp"
// Some helper functions for this tutorial:
#include "vector-io.hpp"
template<typename ScalarType>
void run_tutorial()
{
typedef mtl::dense2D<ScalarType> MTL4DenseMatrix;
typedef mtl::compressed2D<ScalarType> MTL4SparseMatrix;
mtl::dense2D<ScalarType> mtl4_densemat(5, 5);
mtl::dense2D<ScalarType> mtl4_densemat2(5, 5);
mtl4_densemat(0,0) = 2.0; mtl4_densemat(0,1) = -1.0;
mtl4_densemat(1,0) = -1.0; mtl4_densemat(1,1) = 2.0; mtl4_densemat(1,2) = -1.0;
mtl4_densemat(2,1) = -1.0; mtl4_densemat(2,2) = -1.0; mtl4_densemat(2,3) = -1.0;
mtl4_densemat(3,2) = -1.0; mtl4_densemat(3,3) = 2.0; mtl4_densemat(3,4) = -1.0;
mtl4_densemat(4,4) = -1.0; mtl4_densemat(4,4) = -1.0;
MTL4SparseMatrix mtl4_sparsemat;
set_to_zero(mtl4_sparsemat);
mtl4_sparsemat.change_dim(5, 5);
MTL4SparseMatrix mtl4_sparsemat2;
set_to_zero(mtl4_sparsemat2);
mtl4_sparsemat2.change_dim(5, 5);
{
mtl::matrix::inserter< MTL4SparseMatrix > ins(mtl4_sparsemat);
typedef typename mtl::Collection<MTL4SparseMatrix>::value_type ValueType;
ins(0,0) << ValueType(2.0); ins(0,1) << ValueType(-1.0);
ins(1,1) << ValueType(2.0); ins(1,2) << ValueType(-1.0);
ins(2,2) << ValueType(-1.0); ins(2,3) << ValueType(-1.0);
ins(3,3) << ValueType(2.0); ins(3,4) << ValueType(-1.0);
ins(4,4) << ValueType(-1.0);
}
mtl::dense_vector<ScalarType> mtl4_rhs(5, 0.0);
mtl::dense_vector<ScalarType> mtl4_result(5, 0.0);
mtl::dense_vector<ScalarType> mtl4_temp(5, 0.0);
mtl4_rhs(0) = 10.0;
mtl4_rhs(1) = 11.0;
mtl4_rhs(2) = 12.0;
mtl4_rhs(3) = 13.0;
mtl4_rhs(4) = 14.0;
viennacl::vector<ScalarType> vcl_rhs(5);
viennacl::vector<ScalarType> vcl_result(5);
viennacl::matrix<ScalarType> vcl_densemat(5, 5);
viennacl::compressed_matrix<ScalarType> vcl_sparsemat(5, 5);
viennacl::copy(&(mtl4_rhs[0]), &(mtl4_rhs[0]) + 5, vcl_rhs.begin()); //method 1: via iterator interface (cf. std::copy())
viennacl::copy(mtl4_rhs, vcl_rhs); //method 2: via built-in wrappers (convenience layer)
viennacl::copy(mtl4_densemat, vcl_densemat);
viennacl::copy(mtl4_sparsemat, vcl_sparsemat);
// For completeness: Copy matrices from ViennaCL back to Eigen:
viennacl::copy(vcl_densemat, mtl4_densemat2);
viennacl::copy(vcl_sparsemat, mtl4_sparsemat2);
mtl4_result = mtl4_densemat * mtl4_rhs;
vcl_result = viennacl::linalg::prod(vcl_densemat, vcl_rhs);
viennacl::copy(vcl_result, mtl4_temp);
mtl4_result -= mtl4_temp;
std::cout << "Difference for dense matrix-vector product: " << mtl::two_norm(mtl4_result) << std::endl;
mtl4_result = mtl4_densemat2 * mtl4_rhs - mtl4_temp;
std::cout << "Difference for dense matrix-vector product (MTL4->ViennaCL->MTL4): "
<< mtl::two_norm(mtl4_result) << std::endl;
mtl4_result = mtl4_sparsemat * mtl4_rhs;
vcl_result = viennacl::linalg::prod(vcl_sparsemat, vcl_rhs);
viennacl::copy(vcl_result, mtl4_temp);
mtl4_result -= mtl4_temp;
std::cout << "Difference for sparse matrix-vector product: " << mtl::two_norm(mtl4_result) << std::endl;
mtl4_result = mtl4_sparsemat2 * mtl4_rhs - mtl4_temp;
std::cout << "Difference for sparse matrix-vector product (MTL4->ViennaCL->MTL4): "
<< mtl::two_norm(mtl4_result) << std::endl;
}
int main(int, char *[])
{
std::cout << "----------------------------------------------" << std::endl;
std::cout << "## Single precision" << std::endl;
std::cout << "----------------------------------------------" << std::endl;
run_tutorial<float>();
#ifdef VIENNACL_HAVE_OPENCL
if ( viennacl::ocl::current_device().double_support() )
#endif
{
std::cout << "----------------------------------------------" << std::endl;
std::cout << "## Double precision" << std::endl;
std::cout << "----------------------------------------------" << std::endl;
run_tutorial<double>();
}
std::cout << std::endl;
std::cout << "!!!! TUTORIAL COMPLETED SUCCESSFULLY !!!!" << std::endl;
std::cout << std::endl;
}