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sparse.cpp

This tutorial demonstrates the use of sparse matrices. The primary operation for sparse matrices in ViennaCL is the sparse matrix-vector product.

We start with including the respective headers:

// system headers
#include <iostream>
// ublas headers
#include <boost/numeric/ublas/matrix_sparse.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/operation.hpp>
#include <boost/numeric/ublas/operation_sparse.hpp>
#include <boost/numeric/ublas/io.hpp>
// Must be set if you want to use ViennaCL algorithms on ublas objects
#define VIENNACL_WITH_UBLAS 1
// ViennaCL includes
#include "viennacl/scalar.hpp"
#include "viennacl/vector.hpp"
#include "viennacl/compressed_matrix.hpp"
#include "viennacl/linalg/prod.hpp"
// Additional helper functions for this tutorial:
#include "vector-io.hpp"
// Shortcut for writing 'ublas::' instead of 'boost::numeric::ublas::'
using namespace boost::numeric;

We setup a sparse matrix in uBLAS and populate it with values. Then, the respective ViennaCL sparse matrix is created and initialized with data from the uBLAS matrix. After a direct manipulation of the ViennaCL matrix, matrix-vector products are computed with both matrices.

int main()
{
typedef float ScalarType;
std::size_t size = 5;

Set up some ublas objects

ublas::vector<ScalarType> rhs = ublas::scalar_vector<ScalarType>(size, ScalarType(size));
ublas::compressed_matrix<ScalarType> ublas_matrix(size, size);
ublas_matrix(0,0) = 2.0f; ublas_matrix(0,1) = -1.0f;
ublas_matrix(1,0) = -1.0f; ublas_matrix(1,1) = 2.0f; ublas_matrix(1,2) = -1.0f;
ublas_matrix(2,1) = -1.0f; ublas_matrix(2,2) = 2.0f; ublas_matrix(2,3) = -1.0f;
ublas_matrix(3,2) = -1.0f; ublas_matrix(3,3) = 2.0f; ublas_matrix(3,4) = -1.0f;
ublas_matrix(4,3) = -1.0f; ublas_matrix(4,4) = 2.0f;
std::cout << "ublas matrix: " << ublas_matrix << std::endl;

Set up some ViennaCL objects and initialize with data from uBLAS objects

viennacl::vector<ScalarType> vcl_rhs(size);
viennacl::compressed_matrix<ScalarType> vcl_compressed_matrix(size, size);
viennacl::copy(rhs, vcl_rhs);
viennacl::copy(ublas_matrix, vcl_compressed_matrix);
// just get the data directly from the GPU and print it:
ublas::compressed_matrix<ScalarType> temp(size, size);
viennacl::copy(vcl_compressed_matrix, temp);
std::cout << "ViennaCL: " << temp << std::endl;
// now modify GPU data directly:
std::cout << "Modifying vcl_compressed_matrix a bit: " << std::endl;
vcl_compressed_matrix(0, 0) = 3.0f;
vcl_compressed_matrix(2, 3) = -3.0f;
vcl_compressed_matrix(4, 2) = -3.0f; //this is a new nonzero entry
vcl_compressed_matrix(4, 3) = -3.0f;
// and print it again:
viennacl::copy(vcl_compressed_matrix, temp);
std::cout << "ViennaCL matrix copied to uBLAS matrix: " << temp << std::endl;

Compute matrix-vector products and output the results (should match):

std::cout << "ublas: " << ublas::prod(temp, rhs) << std::endl;
std::cout << "ViennaCL: " << viennacl::linalg::prod(vcl_compressed_matrix, vcl_rhs) << std::endl;

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

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

## 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>
// ublas headers
#include <boost/numeric/ublas/matrix_sparse.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/operation.hpp>
#include <boost/numeric/ublas/operation_sparse.hpp>
#include <boost/numeric/ublas/io.hpp>
// Must be set if you want to use ViennaCL algorithms on ublas objects
#define VIENNACL_WITH_UBLAS 1
// ViennaCL includes
#include "viennacl/scalar.hpp"
#include "viennacl/vector.hpp"
#include "viennacl/compressed_matrix.hpp"
#include "viennacl/linalg/prod.hpp"
// Additional helper functions for this tutorial:
#include "vector-io.hpp"
// Shortcut for writing 'ublas::' instead of 'boost::numeric::ublas::'
using namespace boost::numeric;
int main()
{
typedef float ScalarType;
std::size_t size = 5;
ublas::vector<ScalarType> rhs = ublas::scalar_vector<ScalarType>(size, ScalarType(size));
ublas::compressed_matrix<ScalarType> ublas_matrix(size, size);
ublas_matrix(0,0) = 2.0f; ublas_matrix(0,1) = -1.0f;
ublas_matrix(1,0) = -1.0f; ublas_matrix(1,1) = 2.0f; ublas_matrix(1,2) = -1.0f;
ublas_matrix(2,1) = -1.0f; ublas_matrix(2,2) = 2.0f; ublas_matrix(2,3) = -1.0f;
ublas_matrix(3,2) = -1.0f; ublas_matrix(3,3) = 2.0f; ublas_matrix(3,4) = -1.0f;
ublas_matrix(4,3) = -1.0f; ublas_matrix(4,4) = 2.0f;
std::cout << "ublas matrix: " << ublas_matrix << std::endl;
viennacl::vector<ScalarType> vcl_rhs(size);
viennacl::compressed_matrix<ScalarType> vcl_compressed_matrix(size, size);
viennacl::copy(rhs, vcl_rhs);
viennacl::copy(ublas_matrix, vcl_compressed_matrix);
// just get the data directly from the GPU and print it:
ublas::compressed_matrix<ScalarType> temp(size, size);
viennacl::copy(vcl_compressed_matrix, temp);
std::cout << "ViennaCL: " << temp << std::endl;
// now modify GPU data directly:
std::cout << "Modifying vcl_compressed_matrix a bit: " << std::endl;
vcl_compressed_matrix(0, 0) = 3.0f;
vcl_compressed_matrix(2, 3) = -3.0f;
vcl_compressed_matrix(4, 2) = -3.0f; //this is a new nonzero entry
vcl_compressed_matrix(4, 3) = -3.0f;
// and print it again:
viennacl::copy(vcl_compressed_matrix, temp);
std::cout << "ViennaCL matrix copied to uBLAS matrix: " << temp << std::endl;
std::cout << "ublas: " << ublas::prod(temp, rhs) << std::endl;
std::cout << "ViennaCL: " << viennacl::linalg::prod(vcl_compressed_matrix, vcl_rhs) << std::endl;
std::cout << "!!!! TUTORIAL COMPLETED SUCCESSFULLY !!!!" << std::endl;
return EXIT_SUCCESS;
}