/* spdgemv.c

 * 

 * Copyright (C) 2012-2014 Patrick Alken

 * 

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 3 of the License, or (at

 * your option) any later version.

 * 

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

#include <config.h>

#include <stdlib.h>

#include <math.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_vector.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_spmatrix.h>

#include <gsl/gsl_spblas.h>

#include <gsl/gsl_blas.h>

/*

gsl_spblas_dgemv()

  Multiply a sparse matrix and a vector

Inputs: alpha - scalar factor

        A     - sparse matrix

        x     - dense vector

        beta  - scalar factor

        y     - (input/output) dense vector

Return: y = alpha*op(A)*x + beta*y

*/

int

gsl_spblas_dgemv(const CBLAS_TRANSPOSE_t TransA, const double alpha,

                 const gsl_spmatrix *A, const gsl_vector *x,

                 const double beta, gsl_vector *y)

{

  const size_t M = A->size1;

  const size_t N = A->size2;

  if ((TransA == CblasNoTrans && N != x->size) ||

      (TransA == CblasTrans && M != x->size))

    {

      GSL_ERROR("invalid length of x vector", GSL_EBADLEN);

    }

  else if ((TransA == CblasNoTrans && M != y->size) ||

           (TransA == CblasTrans && N != y->size))

    {

      GSL_ERROR("invalid length of y vector", GSL_EBADLEN);

    }

  else

    {

      size_t j, p;

      size_t incX, incY;

      size_t lenX, lenY;

      double *X, *Y;

      double *Ad;

      size_t *Ap, *Ai, *Aj;

      if (TransA == CblasNoTrans)

        {

          lenX = N;

          lenY = M;

        }

      else

        {

          lenX = M;

          lenY = N;

        }

      /* form y := beta*y */

      Y = y->data;

      incY = y->stride;

      if (beta == 0.0)

        {

          size_t jy = 0;

          for (j = 0; j < lenY; ++j)

            {

              Y[jy] = 0.0;

              jy += incY;

            }

        }

      else if (beta != 1.0)

        {

          size_t jy = 0;

          for (j = 0; j < lenY; ++j)

            {

              Y[jy] *= beta;

              jy += incY;

            }

        }

      if (alpha == 0.0)

        return GSL_SUCCESS;

      /* form y := alpha*op(A)*x + y */

      Ap = A->p;

      Ad = A->data;

      X = x->data;

      incX = x->stride;

      if ((GSL_SPMATRIX_ISCCS(A) && (TransA == CblasNoTrans)) ||

          (GSL_SPMATRIX_ISCRS(A) && (TransA == CblasTrans)))

        {

          Ai = A->i;

          for (j = 0; j < lenX; ++j)

            {

              for (p = Ap[j]; p < Ap[j + 1]; ++p)

                {

                  Y[Ai[p] * incY] += alpha * Ad[p] * X[j * incX];

                }

            }

        }

      else if ((GSL_SPMATRIX_ISCCS(A) && (TransA == CblasTrans)) ||

               (GSL_SPMATRIX_ISCRS(A) && (TransA == CblasNoTrans)))

        {

          Ai = A->i;

          for (j = 0; j < lenY; ++j)

            {

              for (p = Ap[j]; p < Ap[j + 1]; ++p)

                {

                  Y[j * incY] += alpha * Ad[p] * X[Ai[p] * incX];

                }

            }

        }

      else if (GSL_SPMATRIX_ISTRIPLET(A))

        {

          if (TransA == CblasNoTrans)

            {

              Ai = A->i;

              Aj = A->p;

            }

          else

            {

              Ai = A->p;

              Aj = A->i;

            }

          for (p = 0; p < A->nz; ++p)

            {

              Y[Ai[p] * incY] += alpha * Ad[p] * X[Aj[p] * incX];

            }

        }

      else

        {

          GSL_ERROR("unsupported matrix type", GSL_EINVAL);

        }

      return GSL_SUCCESS;

    }

} /* gsl_spblas_dgemv() */