vector-range.cpp

This tutorial explains the use of vector ranges with simple BLAS level 1 and 2 operations. Vector slices are used similarly and not further considered in this tutorial.

We start with including the required headers:

// Activate ublas support in ViennaCL
#define VIENNACL_WITH_UBLAS

// System headers
#include <iostream>
#include <string>

// ViennaCL headers
#include "viennacl/scalar.hpp"
#include "viennacl/matrix.hpp"
#include "viennacl/linalg/prod.hpp"
#include "viennacl/vector_proxy.hpp"

// Boost headers
#include "boost/numeric/ublas/vector.hpp"
#include "boost/numeric/ublas/vector_proxy.hpp"
#include "boost/numeric/ublas/io.hpp"

In the main() routine a couple of vectors from both Boost.uBLAS and ViennaCL are set up. Then, subvectors are extracted and manipulated using the usual operator overloads.

int main (int, const char **)
{
  //feel free to change the floating point type to 'double' if supported by your hardware
  typedef float                                           ScalarType;

  typedef boost::numeric::ublas::vector<ScalarType>       VectorType;
  typedef viennacl::vector<ScalarType>                    VCLVectorType;

  std::size_t dim_large = 7;
  std::size_t dim_small = 3;

Setup ublas objects and fill with data:

VectorType ublas_v1(dim_large);
VectorType ublas_v2(dim_small);

for (std::size_t i=0; i<ublas_v1.size(); ++i)
  ublas_v1(i) = ScalarType(i+1);

for (std::size_t i=0; i<ublas_v2.size(); ++i)
  ublas_v2(i) = ScalarType(dim_large + i);

Extract submatrices using the ranges in ublas

boost::numeric::ublas::range ublas_r1(0, dim_small); //the first 'dim_small' entries
boost::numeric::ublas::range ublas_r2(dim_small - 1, 2*dim_small - 1); // 'dim_small' entries somewhere from the middle
boost::numeric::ublas::range ublas_r3(dim_large - dim_small, dim_large); // the last 'dim_small' entries
boost::numeric::ublas::vector_range<VectorType> ublas_v1_sub1(ublas_v1, ublas_r1); // front part of vector v_1
boost::numeric::ublas::vector_range<VectorType> ublas_v1_sub2(ublas_v1, ublas_r2); // center part of vector v_1
boost::numeric::ublas::vector_range<VectorType> ublas_v1_sub3(ublas_v1, ublas_r3); // tail of vector v_1

Create ViennaCL objects and copy data over from uBLAS objects.

VCLVectorType vcl_v1(dim_large);
VCLVectorType vcl_v2(dim_small);

viennacl::copy(ublas_v1, vcl_v1);
viennacl::copy(ublas_v2, vcl_v2);

Extract submatrices using the range-functionality in ViennaCL. This works exactly the same way as for uBLAS.

viennacl::range vcl_r1(0, dim_small); //the first 'dim_small' entries
viennacl::range vcl_r2(dim_small - 1, 2*dim_small - 1);  // 'dim_small' entries somewhere from the middle
viennacl::range vcl_r3(dim_large - dim_small, dim_large);  // the last 'dim_small' entries
viennacl::vector_range<VCLVectorType>   vcl_v1_sub1(vcl_v1, vcl_r1); // front part of vector v_1
viennacl::vector_range<VCLVectorType>   vcl_v1_sub2(vcl_v1, vcl_r2); // center part of vector v_1
viennacl::vector_range<VCLVectorType>   vcl_v1_sub3(vcl_v1, vcl_r3); // tail of vector v_1

Copy from ublas to submatrices and back:

ublas_v1_sub1 = ublas_v2;
viennacl::copy(ublas_v2, vcl_v1_sub1);
viennacl::copy(vcl_v1_sub1, ublas_v2);

Addition of subvectors:

ublas_v1_sub1 += ublas_v1_sub1;
vcl_v1_sub1 += vcl_v1_sub1;

ublas_v1_sub2 += ublas_v1_sub2;
vcl_v1_sub2 += vcl_v1_sub2;

ublas_v1_sub3 += ublas_v1_sub3;
vcl_v1_sub3 += vcl_v1_sub3;

Print full vectors. Notice that the various entries have changed according to the subvector manipulations above.

std::cout << "ublas:    " << ublas_v1 << std::endl;
std::cout << "ViennaCL: " << vcl_v1 << std::endl;

That's it. Print 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
============================================================================= */

// Activate ublas support in ViennaCL
#define VIENNACL_WITH_UBLAS

// System headers
#include <iostream>
#include <string>

// ViennaCL headers
#include "viennacl/scalar.hpp"
#include "viennacl/matrix.hpp"
#include "viennacl/linalg/prod.hpp"
#include "viennacl/vector_proxy.hpp"

// Boost headers
#include "boost/numeric/ublas/vector.hpp"
#include "boost/numeric/ublas/vector_proxy.hpp"
#include "boost/numeric/ublas/io.hpp"

int main (int, const char **)
{
  //feel free to change the floating point type to 'double' if supported by your hardware
  typedef float                                           ScalarType;

  typedef boost::numeric::ublas::vector<ScalarType>       VectorType;
  typedef viennacl::vector<ScalarType>                    VCLVectorType;

  std::size_t dim_large = 7;
  std::size_t dim_small = 3;

  VectorType ublas_v1(dim_large);
  VectorType ublas_v2(dim_small);

  for (std::size_t i=0; i<ublas_v1.size(); ++i)
    ublas_v1(i) = ScalarType(i+1);

  for (std::size_t i=0; i<ublas_v2.size(); ++i)
    ublas_v2(i) = ScalarType(dim_large + i);


  boost::numeric::ublas::range ublas_r1(0, dim_small); //the first 'dim_small' entries
  boost::numeric::ublas::range ublas_r2(dim_small - 1, 2*dim_small - 1); // 'dim_small' entries somewhere from the middle
  boost::numeric::ublas::range ublas_r3(dim_large - dim_small, dim_large); // the last 'dim_small' entries
  boost::numeric::ublas::vector_range<VectorType> ublas_v1_sub1(ublas_v1, ublas_r1); // front part of vector v_1
  boost::numeric::ublas::vector_range<VectorType> ublas_v1_sub2(ublas_v1, ublas_r2); // center part of vector v_1
  boost::numeric::ublas::vector_range<VectorType> ublas_v1_sub3(ublas_v1, ublas_r3); // tail of vector v_1


  VCLVectorType vcl_v1(dim_large);
  VCLVectorType vcl_v2(dim_small);

  viennacl::copy(ublas_v1, vcl_v1);
  viennacl::copy(ublas_v2, vcl_v2);


  viennacl::range vcl_r1(0, dim_small); //the first 'dim_small' entries
  viennacl::range vcl_r2(dim_small - 1, 2*dim_small - 1);  // 'dim_small' entries somewhere from the middle
  viennacl::range vcl_r3(dim_large - dim_small, dim_large);  // the last 'dim_small' entries
  viennacl::vector_range<VCLVectorType>   vcl_v1_sub1(vcl_v1, vcl_r1); // front part of vector v_1
  viennacl::vector_range<VCLVectorType>   vcl_v1_sub2(vcl_v1, vcl_r2); // center part of vector v_1
  viennacl::vector_range<VCLVectorType>   vcl_v1_sub3(vcl_v1, vcl_r3); // tail of vector v_1


  ublas_v1_sub1 = ublas_v2;
  viennacl::copy(ublas_v2, vcl_v1_sub1);
  viennacl::copy(vcl_v1_sub1, ublas_v2);

  ublas_v1_sub1 += ublas_v1_sub1;
  vcl_v1_sub1 += vcl_v1_sub1;

  ublas_v1_sub2 += ublas_v1_sub2;
  vcl_v1_sub2 += vcl_v1_sub2;

  ublas_v1_sub3 += ublas_v1_sub3;
  vcl_v1_sub3 += vcl_v1_sub3;

  std::cout << "ublas:    " << ublas_v1 << std::endl;
  std::cout << "ViennaCL: " << vcl_v1 << std::endl;

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

  return EXIT_SUCCESS;
}