text: /* 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 2 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., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  {
    INDEX i, j;
    INDEX lenX, lenY, L, U;
  
    const int Trans = (TransA != CblasConjTrans) ? TransA : CblasTrans;
  
    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");
    }
  }
  