source_symv.h

开放gsl矩阵运算

/* blas/source_symv.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;

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

  /* form  y := beta*y */
  if (beta == 0.0) {
    INDEX iy = OFFSET(N, incY);
    for (i = 0; i < N; i++) {
      Y[iy] = 0.0;
      iy += incY;
    }
  } else if (beta != 1.0) {
    INDEX iy = OFFSET(N, incY);
    for (i = 0; i < N; i++) {
      Y[iy] *= beta;
      iy += incY;
    }
  }

  if (alpha == 0.0)
    return;

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

  if ((order == CblasRowMajor && Uplo == CblasUpper)
      || (order == CblasColMajor && Uplo == CblasLower)) {
    INDEX ix = OFFSET(N, incX);
    INDEX iy = OFFSET(N, incY);
    for (i = 0; i < N; i++) {
      BASE temp1 = alpha * X[ix];
      BASE temp2 = 0.0;
      const INDEX j_min = i + 1;
      const INDEX j_max = N;
      INDEX jx = OFFSET(N, incX) + j_min * incX;
      INDEX jy = OFFSET(N, incY) + j_min * incY;
      Y[iy] += temp1 * A[lda * i + i];
      for (j = j_min; j < j_max; j++) {
	Y[jy] += temp1 * A[lda * i + j];
	temp2 += X[jx] * A[lda * i + j];
	jx += incX;
	jy += incY;
      }
      Y[iy] += alpha * temp2;
      ix += incX;
      iy += incY;
    }
  } else if ((order == CblasRowMajor && Uplo == CblasLower)
	     || (order == CblasColMajor && Uplo == CblasUpper)) {
    INDEX ix = OFFSET(N, incX) + (N - 1) * incX;
    INDEX iy = OFFSET(N, incY) + (N - 1) * incY;
    for (i = N; i > 0 && i--;) {
      BASE temp1 = alpha * X[ix];
      BASE temp2 = 0.0;
      const INDEX j_min = 0;
      const INDEX j_max = i;
      INDEX jx = OFFSET(N, incX) + j_min * incX;
      INDEX jy = OFFSET(N, incY) + j_min * incY;
      Y[iy] += temp1 * A[lda * i + i];
      for (j = j_min; j < j_max; j++) {
	Y[jy] += temp1 * A[lda * i + j];
	temp2 += X[jx] * A[lda * i + j];
	jx += incX;
	jy += incY;
      }
      Y[iy] += alpha * temp2;
      ix -= incX;
      iy -= incY;
    }
  } else {
    BLAS_ERROR("unrecognized operation");
  }
}