/* blas/source_gbmv_r.h

 *

 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman

 *

 * 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.

 */

{

  INDEX i, j;

  INDEX lenX, lenY, L, U;

  const int Trans = (TransA != CblasConjTrans) ? TransA : CblasTrans;

  CHECK_ARGS14(GBMV,order,TransA,M,N,KL,KU,alpha,A,lda,X,incX,beta,Y,incY);

  if (M == 0 || N == 0)

    return;

  if (alpha == 0.0 && beta == 1.0)

    return;

  if (Trans == CblasNoTrans) {

    lenX = N;

    lenY = M;

    L = KL;

    U = KU;

  } else {

    lenX = M;

    lenY = N;

    L = KU;

    U = KL;

  }

  /* form  y := beta*y */

  if (beta == 0.0) {

    INDEX iy = OFFSET(lenY, incY);

    for (i = 0; i < lenY; i++) {

      Y[iy] = 0;

      iy += incY;

    }

  } else if (beta != 1.0) {

    INDEX iy = OFFSET(lenY, incY);

    for (i = 0; i < lenY; i++) {

      Y[iy] *= beta;

      iy += incY;

    }

  }

  if (alpha == 0.0)

    return;

  if ((order == CblasRowMajor && Trans == CblasNoTrans)

      || (order == CblasColMajor && Trans == CblasTrans)) {

    /* form  y := alpha*A*x + y */

    INDEX iy = OFFSET(lenY, incY);

    for (i = 0; i < lenY; i++) {

      BASE temp = 0.0;

      const INDEX j_min = (i > L ? i - L : 0);

      const INDEX j_max = GSL_MIN(lenX, i + U + 1);

      INDEX jx = OFFSET(lenX, incX) + j_min * incX;

      for (j = j_min; j < j_max; j++) {

        temp += X[jx] * A[(L - i + j) + i * lda];

        jx += incX;

      }

      Y[iy] += alpha * temp;

      iy += incY;

    }

  } else if ((order == CblasRowMajor && Trans == CblasTrans)

             || (order == CblasColMajor && Trans == CblasNoTrans)) {

    /* form  y := alpha*A'*x + y */

    INDEX jx = OFFSET(lenX, incX);

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

      const BASE temp = alpha * X[jx];

      if (temp != 0.0) {

        const INDEX i_min = (j > U ? j - U : 0);

        const INDEX i_max = GSL_MIN(lenY, j + L + 1);

        INDEX iy = OFFSET(lenY, incY) + i_min * incY;

        for (i = i_min; i < i_max; i++) {

          Y[iy] += temp * A[lda * j + (U + i - j)];

          iy += incY;

        }

      }

      jx += incX;

    }

  } else {

    BLAS_ERROR("unrecognized operation");

  }

}