Description of __mult

__mult_dim		Programmers Guide
		Contents \| Index \| Search

Category:algorithms

Component type:function

Prototype

template <class Matrix, class VecX, class VecY> void __mult_dim(const Matrix& A, const VecX& x, VecY y, oned_tag) ;

Description

Multiplies matrix A times vector x and stores the result in vector y.

Note: ignore the oned_tag parameter and the underscores in the name of this function.

Definition

mtl.h

Requirements on types

Matrix::value_type, VecX::value_type, and VecY::value_type must be the same type
the multiplication operator must be defined for Matrix::value_type
the addition operator must be defined for Matrix::value_type

Preconditions

A.nrows() <= y.size()
A.ncols() <= x.size()
x and y not same vector

Complexity

Example

In general_matvec_mult.cc:

  typedef matrix< double, 
                  rectangle<2,2>, 
                  dense<external>, 
                  column_major>::type Matrix; 
  typedef dense1D<double> Vector;
  double pi, theta;
  double dA[4];
  Matrix rot(dA);
  Vector vec1(Matrix::N),vec2(Matrix::N);

  pi = 4.0 * atan (1.0);
  theta = pi / 2.0;

  rot(0,0) = cos(theta);
  rot(1,0) = sin(theta);
  rot(0,1) = -sin(theta);
  rot(1,1) = cos(theta);

  vec1[0] = 3.0;
  vec1[1] = 4.0;
  mult(rot, scaled(vec1, 0.5), vec2);

More examples can be found in banded_matvec_mult.cc, symm_matvec_mult.ccsymm_matvec_mult.cc

Notes

See also