Exemplo n.º 1
0
/* Subroutine */ int PASTEF77(z,hbmv)(character *uplo, integer *n, integer *k, doublecomplex *alpha, doublecomplex *a, integer *lda, doublecomplex *x, integer * incx, doublecomplex *beta, doublecomplex *y, integer *incy)
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3, i__4, i__5;
    doublereal d__1;
    doublecomplex z__1, z__2, z__3, z__4;

    /* Builtin functions */
    void bla_d_cnjg(doublecomplex *, doublecomplex *);

    /* Local variables */
    integer info;
    doublecomplex temp1, temp2;
    integer i__, j, l;
    extern logical PASTEF770(lsame)(character *, character *, ftnlen, ftnlen);
    integer kplus1, ix, iy, jx, jy, kx, ky;
    extern /* Subroutine */ int PASTEF770(xerbla)(character *, integer *, ftnlen);

/*     .. Scalar Arguments .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  ZHBMV  performs the matrix-vector  operation */

/*     y := alpha*A*x + beta*y, */

/*  where alpha and beta are scalars, x and y are n element vectors and */
/*  A is an n by n hermitian band matrix, with k super-diagonals. */

/*  Parameters */
/*  ========== */

/*  UPLO   - CHARACTER*1. */
/*           On entry, UPLO specifies whether the upper or lower */
/*           triangular part of the band matrix A is being supplied as */
/*           follows: */

/*              UPLO = 'U' or 'u'   The upper triangular part of A is */
/*                                  being supplied. */

/*              UPLO = 'L' or 'l'   The lower triangular part of A is */
/*                                  being supplied. */

/*           Unchanged on exit. */

/*  N      - INTEGER. */
/*           On entry, N specifies the order of the matrix A. */
/*           N must be at least zero. */
/*           Unchanged on exit. */

/*  K      - INTEGER. */
/*           On entry, K specifies the number of super-diagonals of the */
/*           matrix A. K must satisfy  0 .le. K. */
/*           Unchanged on exit. */

/*  ALPHA  - COMPLEX*16      . */
/*           On entry, ALPHA specifies the scalar alpha. */
/*           Unchanged on exit. */

/*  A      - COMPLEX*16       array of DIMENSION ( LDA, n ). */
/*           Before entry with UPLO = 'U' or 'u', the leading ( k + 1 ) */
/*           by n part of the array A must contain the upper triangular */
/*           band part of the hermitian matrix, supplied column by */
/*           column, with the leading diagonal of the matrix in row */
/*           ( k + 1 ) of the array, the first super-diagonal starting at */
/*           position 2 in row k, and so on. The top left k by k triangle */
/*           of the array A is not referenced. */
/*           The following program segment will transfer the upper */
/*           triangular part of a hermitian band matrix from conventional */
/*           full matrix storage to band storage: */

/*                 DO 20, J = 1, N */
/*                    M = K + 1 - J */
/*                    DO 10, I = MAX( 1, J - K ), J */
/*                       A( M + I, J ) = matrix( I, J ) */
/*              10    CONTINUE */
/*              20 CONTINUE */

/*           Before entry with UPLO = 'L' or 'l', the leading ( k + 1 ) */
/*           by n part of the array A must contain the lower triangular */
/*           band part of the hermitian matrix, supplied column by */
/*           column, with the leading diagonal of the matrix in row 1 of */
/*           the array, the first sub-diagonal starting at position 1 in */
/*           row 2, and so on. The bottom right k by k triangle of the */
/*           array A is not referenced. */
/*           The following program segment will transfer the lower */
/*           triangular part of a hermitian band matrix from conventional */
/*           full matrix storage to band storage: */

/*                 DO 20, J = 1, N */
/*                    M = 1 - J */
/*                    DO 10, I = J, MIN( N, J + K ) */
/*                       A( M + I, J ) = matrix( I, J ) */
/*              10    CONTINUE */
/*              20 CONTINUE */

/*           Note that the imaginary parts of the diagonal elements need */
/*           not be set and are assumed to be zero. */
/*           Unchanged on exit. */

/*  LDA    - INTEGER. */
/*           On entry, LDA specifies the first dimension of A as declared */
/*           in the calling (sub) program. LDA must be at least */
/*           ( k + 1 ). */
/*           Unchanged on exit. */

/*  X      - COMPLEX*16       array of DIMENSION at least */
/*           ( 1 + ( n - 1 )*abs( INCX ) ). */
/*           Before entry, the incremented array X must contain the */
/*           vector x. */
/*           Unchanged on exit. */

/*  INCX   - INTEGER. */
/*           On entry, INCX specifies the increment for the elements of */
/*           X. INCX must not be zero. */
/*           Unchanged on exit. */

/*  BETA   - COMPLEX*16      . */
/*           On entry, BETA specifies the scalar beta. */
/*           Unchanged on exit. */

/*  Y      - COMPLEX*16       array of DIMENSION at least */
/*           ( 1 + ( n - 1 )*abs( INCY ) ). */
/*           Before entry, the incremented array Y must contain the */
/*           vector y. On exit, Y is overwritten by the updated vector y. */

/*  INCY   - INTEGER. */
/*           On entry, INCY specifies the increment for the elements of */
/*           Y. INCY must not be zero. */
/*           Unchanged on exit. */


/*  Level 2 Blas routine. */

/*  -- Written on 22-October-1986. */
/*     Jack Dongarra, Argonne National Lab. */
/*     Jeremy Du Croz, Nag Central Office. */
/*     Sven Hammarling, Nag Central Office. */
/*     Richard Hanson, Sandia National Labs. */


/*     .. Parameters .. */
/*     .. Local Scalars .. */
/*     .. External Functions .. */
/*     .. External Subroutines .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    --x;
    --y;

    /* Function Body */
    info = 0;
    if (! PASTEF770(lsame)(uplo, "U", (ftnlen)1, (ftnlen)1) && ! PASTEF770(lsame)(uplo, "L", (
	    ftnlen)1, (ftnlen)1)) {
	info = 1;
    } else if (*n < 0) {
	info = 2;
    } else if (*k < 0) {
	info = 3;
    } else if (*lda < *k + 1) {
	info = 6;
    } else if (*incx == 0) {
	info = 8;
    } else if (*incy == 0) {
	info = 11;
    }
    if (info != 0) {
	PASTEF770(xerbla)("ZHBMV ", &info, (ftnlen)6);
	return 0;
    }

/*     Quick return if possible. */

    if (*n == 0 || (alpha->real == 0. && alpha->imag == 0. && (beta->real == 1. && 
	    beta->imag == 0.))) {
	return 0;
    }

/*     Set up the start points in  X  and  Y. */

    if (*incx > 0) {
	kx = 1;
    } else {
	kx = 1 - (*n - 1) * *incx;
    }
    if (*incy > 0) {
	ky = 1;
    } else {
	ky = 1 - (*n - 1) * *incy;
    }

/*     Start the operations. In this version the elements of the array A */
/*     are accessed sequentially with one pass through A. */

/*     First form  y := beta*y. */

    if (beta->real != 1. || beta->imag != 0.) {
	if (*incy == 1) {
	    if (beta->real == 0. && beta->imag == 0.) {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    i__2 = i__;
		    y[i__2].real = 0., y[i__2].imag = 0.;
/* L10: */
		}
	    } else {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    i__2 = i__;
		    i__3 = i__;
		    z__1.real = beta->real * y[i__3].real - beta->imag * y[i__3].imag, 
			    z__1.imag = beta->real * y[i__3].imag + beta->imag * y[i__3]
			    .real;
		    y[i__2].real = z__1.real, y[i__2].imag = z__1.imag;
/* L20: */
		}
	    }
	} else {
	    iy = ky;
	    if (beta->real == 0. && beta->imag == 0.) {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    i__2 = iy;
		    y[i__2].real = 0., y[i__2].imag = 0.;
		    iy += *incy;
/* L30: */
		}
	    } else {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    i__2 = iy;
		    i__3 = iy;
		    z__1.real = beta->real * y[i__3].real - beta->imag * y[i__3].imag, 
			    z__1.imag = beta->real * y[i__3].imag + beta->imag * y[i__3]
			    .real;
		    y[i__2].real = z__1.real, y[i__2].imag = z__1.imag;
		    iy += *incy;
/* L40: */
		}
	    }
	}
    }
    if (alpha->real == 0. && alpha->imag == 0.) {
	return 0;
    }
    if (PASTEF770(lsame)(uplo, "U", (ftnlen)1, (ftnlen)1)) {

/*        Form  y  when upper triangle of A is stored. */

	kplus1 = *k + 1;
	if (*incx == 1 && *incy == 1) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__2 = j;
		z__1.real = alpha->real * x[i__2].real - alpha->imag * x[i__2].imag, z__1.imag =
			 alpha->real * x[i__2].imag + alpha->imag * x[i__2].real;
		temp1.real = z__1.real, temp1.imag = z__1.imag;
		temp2.real = 0., temp2.imag = 0.;
		l = kplus1 - j;
/* Computing MAX */
		i__2 = 1, i__3 = j - *k;
		i__4 = j - 1;
		for (i__ = f2c_max(i__2,i__3); i__ <= i__4; ++i__) {
		    i__2 = i__;
		    i__3 = i__;
		    i__5 = l + i__ + j * a_dim1;
		    z__2.real = temp1.real * a[i__5].real - temp1.imag * a[i__5].imag, 
			    z__2.imag = temp1.real * a[i__5].imag + temp1.imag * a[i__5]
			    .real;
		    z__1.real = y[i__3].real + z__2.real, z__1.imag = y[i__3].imag + z__2.imag;
		    y[i__2].real = z__1.real, y[i__2].imag = z__1.imag;
		    bla_d_cnjg(&z__3, &a[l + i__ + j * a_dim1]);
		    i__2 = i__;
		    z__2.real = z__3.real * x[i__2].real - z__3.imag * x[i__2].imag, z__2.imag =
			     z__3.real * x[i__2].imag + z__3.imag * x[i__2].real;
		    z__1.real = temp2.real + z__2.real, z__1.imag = temp2.imag + z__2.imag;
		    temp2.real = z__1.real, temp2.imag = z__1.imag;
/* L50: */
		}
		i__4 = j;
		i__2 = j;
		i__3 = kplus1 + j * a_dim1;
		d__1 = a[i__3].real;
		z__3.real = d__1 * temp1.real, z__3.imag = d__1 * temp1.imag;
		z__2.real = y[i__2].real + z__3.real, z__2.imag = y[i__2].imag + z__3.imag;
		z__4.real = alpha->real * temp2.real - alpha->imag * temp2.imag, z__4.imag = 
			alpha->real * temp2.imag + alpha->imag * temp2.real;
		z__1.real = z__2.real + z__4.real, z__1.imag = z__2.imag + z__4.imag;
		y[i__4].real = z__1.real, y[i__4].imag = z__1.imag;
/* L60: */
	    }
	} else {
	    jx = kx;
	    jy = ky;
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__4 = jx;
		z__1.real = alpha->real * x[i__4].real - alpha->imag * x[i__4].imag, z__1.imag =
			 alpha->real * x[i__4].imag + alpha->imag * x[i__4].real;
		temp1.real = z__1.real, temp1.imag = z__1.imag;
		temp2.real = 0., temp2.imag = 0.;
		ix = kx;
		iy = ky;
		l = kplus1 - j;
/* Computing MAX */
		i__4 = 1, i__2 = j - *k;
		i__3 = j - 1;
		for (i__ = f2c_max(i__4,i__2); i__ <= i__3; ++i__) {
		    i__4 = iy;
		    i__2 = iy;
		    i__5 = l + i__ + j * a_dim1;
		    z__2.real = temp1.real * a[i__5].real - temp1.imag * a[i__5].imag, 
			    z__2.imag = temp1.real * a[i__5].imag + temp1.imag * a[i__5]
			    .real;
		    z__1.real = y[i__2].real + z__2.real, z__1.imag = y[i__2].imag + z__2.imag;
		    y[i__4].real = z__1.real, y[i__4].imag = z__1.imag;
		    bla_d_cnjg(&z__3, &a[l + i__ + j * a_dim1]);
		    i__4 = ix;
		    z__2.real = z__3.real * x[i__4].real - z__3.imag * x[i__4].imag, z__2.imag =
			     z__3.real * x[i__4].imag + z__3.imag * x[i__4].real;
		    z__1.real = temp2.real + z__2.real, z__1.imag = temp2.imag + z__2.imag;
		    temp2.real = z__1.real, temp2.imag = z__1.imag;
		    ix += *incx;
		    iy += *incy;
/* L70: */
		}
		i__3 = jy;
		i__4 = jy;
		i__2 = kplus1 + j * a_dim1;
		d__1 = a[i__2].real;
		z__3.real = d__1 * temp1.real, z__3.imag = d__1 * temp1.imag;
		z__2.real = y[i__4].real + z__3.real, z__2.imag = y[i__4].imag + z__3.imag;
		z__4.real = alpha->real * temp2.real - alpha->imag * temp2.imag, z__4.imag = 
			alpha->real * temp2.imag + alpha->imag * temp2.real;
		z__1.real = z__2.real + z__4.real, z__1.imag = z__2.imag + z__4.imag;
		y[i__3].real = z__1.real, y[i__3].imag = z__1.imag;
		jx += *incx;
		jy += *incy;
		if (j > *k) {
		    kx += *incx;
		    ky += *incy;
		}
/* L80: */
	    }
	}
    } else {

/*        Form  y  when lower triangle of A is stored. */

	if (*incx == 1 && *incy == 1) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__3 = j;
		z__1.real = alpha->real * x[i__3].real - alpha->imag * x[i__3].imag, z__1.imag =
			 alpha->real * x[i__3].imag + alpha->imag * x[i__3].real;
		temp1.real = z__1.real, temp1.imag = z__1.imag;
		temp2.real = 0., temp2.imag = 0.;
		i__3 = j;
		i__4 = j;
		i__2 = j * a_dim1 + 1;
		d__1 = a[i__2].real;
		z__2.real = d__1 * temp1.real, z__2.imag = d__1 * temp1.imag;
		z__1.real = y[i__4].real + z__2.real, z__1.imag = y[i__4].imag + z__2.imag;
		y[i__3].real = z__1.real, y[i__3].imag = z__1.imag;
		l = 1 - j;
/* Computing MIN */
		i__4 = *n, i__2 = j + *k;
		i__3 = f2c_min(i__4,i__2);
		for (i__ = j + 1; i__ <= i__3; ++i__) {
		    i__4 = i__;
		    i__2 = i__;
		    i__5 = l + i__ + j * a_dim1;
		    z__2.real = temp1.real * a[i__5].real - temp1.imag * a[i__5].imag, 
			    z__2.imag = temp1.real * a[i__5].imag + temp1.imag * a[i__5]
			    .real;
		    z__1.real = y[i__2].real + z__2.real, z__1.imag = y[i__2].imag + z__2.imag;
		    y[i__4].real = z__1.real, y[i__4].imag = z__1.imag;
		    bla_d_cnjg(&z__3, &a[l + i__ + j * a_dim1]);
		    i__4 = i__;
		    z__2.real = z__3.real * x[i__4].real - z__3.imag * x[i__4].imag, z__2.imag =
			     z__3.real * x[i__4].imag + z__3.imag * x[i__4].real;
		    z__1.real = temp2.real + z__2.real, z__1.imag = temp2.imag + z__2.imag;
		    temp2.real = z__1.real, temp2.imag = z__1.imag;
/* L90: */
		}
		i__3 = j;
		i__4 = j;
		z__2.real = alpha->real * temp2.real - alpha->imag * temp2.imag, z__2.imag = 
			alpha->real * temp2.imag + alpha->imag * temp2.real;
		z__1.real = y[i__4].real + z__2.real, z__1.imag = y[i__4].imag + z__2.imag;
		y[i__3].real = z__1.real, y[i__3].imag = z__1.imag;
/* L100: */
	    }
	} else {
	    jx = kx;
	    jy = ky;
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		i__3 = jx;
		z__1.real = alpha->real * x[i__3].real - alpha->imag * x[i__3].imag, z__1.imag =
			 alpha->real * x[i__3].imag + alpha->imag * x[i__3].real;
		temp1.real = z__1.real, temp1.imag = z__1.imag;
		temp2.real = 0., temp2.imag = 0.;
		i__3 = jy;
		i__4 = jy;
		i__2 = j * a_dim1 + 1;
		d__1 = a[i__2].real;
		z__2.real = d__1 * temp1.real, z__2.imag = d__1 * temp1.imag;
		z__1.real = y[i__4].real + z__2.real, z__1.imag = y[i__4].imag + z__2.imag;
		y[i__3].real = z__1.real, y[i__3].imag = z__1.imag;
		l = 1 - j;
		ix = jx;
		iy = jy;
/* Computing MIN */
		i__4 = *n, i__2 = j + *k;
		i__3 = f2c_min(i__4,i__2);
		for (i__ = j + 1; i__ <= i__3; ++i__) {
		    ix += *incx;
		    iy += *incy;
		    i__4 = iy;
		    i__2 = iy;
		    i__5 = l + i__ + j * a_dim1;
		    z__2.real = temp1.real * a[i__5].real - temp1.imag * a[i__5].imag, 
			    z__2.imag = temp1.real * a[i__5].imag + temp1.imag * a[i__5]
			    .real;
		    z__1.real = y[i__2].real + z__2.real, z__1.imag = y[i__2].imag + z__2.imag;
		    y[i__4].real = z__1.real, y[i__4].imag = z__1.imag;
		    bla_d_cnjg(&z__3, &a[l + i__ + j * a_dim1]);
		    i__4 = ix;
		    z__2.real = z__3.real * x[i__4].real - z__3.imag * x[i__4].imag, z__2.imag =
			     z__3.real * x[i__4].imag + z__3.imag * x[i__4].real;
		    z__1.real = temp2.real + z__2.real, z__1.imag = temp2.imag + z__2.imag;
		    temp2.real = z__1.real, temp2.imag = z__1.imag;
/* L110: */
		}
		i__3 = jy;
		i__4 = jy;
		z__2.real = alpha->real * temp2.real - alpha->imag * temp2.imag, z__2.imag = 
			alpha->real * temp2.imag + alpha->imag * temp2.real;
		z__1.real = y[i__4].real + z__2.real, z__1.imag = y[i__4].imag + z__2.imag;
		y[i__3].real = z__1.real, y[i__3].imag = z__1.imag;
		jx += *incx;
		jy += *incy;
/* L120: */
	    }
	}
    }

    return 0;

/*     End of ZHBMV . */

} /* zhbmv_ */
Exemplo n.º 2
0
/* Subroutine */ int PASTEF77(d,sbmv)(const bla_character *uplo, const bla_integer *n, const bla_integer *k, const bla_double *alpha, const bla_double *a, const bla_integer *lda, const bla_double *x, const bla_integer *incx, const bla_double *beta, bla_double *y, const bla_integer *incy)
{
    /* System generated locals */
    bla_integer a_dim1, a_offset, i__1, i__2, i__3, i__4;

    /* Local variables */
    bla_integer info;
    bla_double temp1, temp2;
    bla_integer i__, j, l;
    //extern bla_logical PASTEF770(lsame)(bla_character *, bla_character *, ftnlen, ftnlen);
    bla_integer kplus1, ix, iy, jx, jy, kx, ky;
    //extern /* Subroutine */ int PASTEF770(xerbla)(bla_character *, bla_integer *, ftnlen);

/*     .. Scalar Arguments .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  DSBMV  performs the matrix-vector  operation */

/*     y := alpha*A*x + beta*y, */

/*  where alpha and beta are scalars, x and y are n element vectors and */
/*  A is an n by n symmetric band matrix, with k super-diagonals. */

/*  Parameters */
/*  ========== */

/*  UPLO   - CHARACTER*1. */
/*           On entry, UPLO specifies whether the upper or lower */
/*           triangular part of the band matrix A is being supplied as */
/*           follows: */

/*              UPLO = 'U' or 'u'   The upper triangular part of A is */
/*                                  being supplied. */

/*              UPLO = 'L' or 'l'   The lower triangular part of A is */
/*                                  being supplied. */

/*           Unchanged on exit. */

/*  N      - INTEGER. */
/*           On entry, N specifies the order of the matrix A. */
/*           N must be at least zero. */
/*           Unchanged on exit. */

/*  K      - INTEGER. */
/*           On entry, K specifies the number of super-diagonals of the */
/*           matrix A. K must satisfy  0 .le. K. */
/*           Unchanged on exit. */

/*  ALPHA  - DOUBLE PRECISION. */
/*           On entry, ALPHA specifies the scalar alpha. */
/*           Unchanged on exit. */

/*  A      - DOUBLE PRECISION array of DIMENSION ( LDA, n ). */
/*           Before entry with UPLO = 'U' or 'u', the leading ( k + 1 ) */
/*           by n part of the array A must contain the upper triangular */
/*           band part of the symmetric matrix, supplied column by */
/*           column, with the leading diagonal of the matrix in row */
/*           ( k + 1 ) of the array, the first super-diagonal starting at */
/*           position 2 in row k, and so on. The top left k by k triangle */
/*           of the array A is not referenced. */
/*           The following program segment will transfer the upper */
/*           triangular part of a symmetric band matrix from conventional */
/*           full matrix storage to band storage: */

/*                 DO 20, J = 1, N */
/*                    M = K + 1 - J */
/*                    DO 10, I = MAX( 1, J - K ), J */
/*                       A( M + I, J ) = matrix( I, J ) */
/*              10    CONTINUE */
/*              20 CONTINUE */

/*           Before entry with UPLO = 'L' or 'l', the leading ( k + 1 ) */
/*           by n part of the array A must contain the lower triangular */
/*           band part of the symmetric matrix, supplied column by */
/*           column, with the leading diagonal of the matrix in row 1 of */
/*           the array, the first sub-diagonal starting at position 1 in */
/*           row 2, and so on. The bottom right k by k triangle of the */
/*           array A is not referenced. */
/*           The following program segment will transfer the lower */
/*           triangular part of a symmetric band matrix from conventional */
/*           full matrix storage to band storage: */

/*                 DO 20, J = 1, N */
/*                    M = 1 - J */
/*                    DO 10, I = J, MIN( N, J + K ) */
/*                       A( M + I, J ) = matrix( I, J ) */
/*              10    CONTINUE */
/*              20 CONTINUE */

/*           Unchanged on exit. */

/*  LDA    - INTEGER. */
/*           On entry, LDA specifies the first dimension of A as declared */
/*           in the calling (sub) program. LDA must be at least */
/*           ( k + 1 ). */
/*           Unchanged on exit. */

/*  X      - DOUBLE PRECISION array of DIMENSION at least */
/*           ( 1 + ( n - 1 )*abs( INCX ) ). */
/*           Before entry, the incremented array X must contain the */
/*           vector x. */
/*           Unchanged on exit. */

/*  INCX   - INTEGER. */
/*           On entry, INCX specifies the increment for the elements of */
/*           X. INCX must not be zero. */
/*           Unchanged on exit. */

/*  BETA   - DOUBLE PRECISION. */
/*           On entry, BETA specifies the scalar beta. */
/*           Unchanged on exit. */

/*  Y      - DOUBLE PRECISION array of DIMENSION at least */
/*           ( 1 + ( n - 1 )*abs( INCY ) ). */
/*           Before entry, the incremented array Y must contain the */
/*           vector y. On exit, Y is overwritten by the updated vector y. */

/*  INCY   - INTEGER. */
/*           On entry, INCY specifies the increment for the elements of */
/*           Y. INCY must not be zero. */
/*           Unchanged on exit. */


/*  Level 2 Blas routine. */

/*  -- Written on 22-October-1986. */
/*     Jack Dongarra, Argonne National Lab. */
/*     Jeremy Du Croz, Nag Central Office. */
/*     Sven Hammarling, Nag Central Office. */
/*     Richard Hanson, Sandia National Labs. */


/*     .. Parameters .. */
/*     .. Local Scalars .. */
/*     .. External Functions .. */
/*     .. External Subroutines .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    --x;
    --y;

    /* Function Body */
    info = 0;
    if (! PASTEF770(lsame)(uplo, "U", (ftnlen)1, (ftnlen)1) && ! PASTEF770(lsame)(uplo, "L", (
	    ftnlen)1, (ftnlen)1)) {
	info = 1;
    } else if (*n < 0) {
	info = 2;
    } else if (*k < 0) {
	info = 3;
    } else if (*lda < *k + 1) {
	info = 6;
    } else if (*incx == 0) {
	info = 8;
    } else if (*incy == 0) {
	info = 11;
    }
    if (info != 0) {
	PASTEF770(xerbla)("DSBMV ", &info, (ftnlen)6);
	return 0;
    }

/*     Quick return if possible. */

    if (*n == 0 || (*alpha == 0. && *beta == 1.)) {
	return 0;
    }

/*     Set up the start points in  X  and  Y. */

    if (*incx > 0) {
	kx = 1;
    } else {
	kx = 1 - (*n - 1) * *incx;
    }
    if (*incy > 0) {
	ky = 1;
    } else {
	ky = 1 - (*n - 1) * *incy;
    }

/*     Start the operations. In this version the elements of the array A */
/*     are accessed sequentially with one pass through A. */

/*     First form  y := beta*y. */

    if (*beta != 1.) {
	if (*incy == 1) {
	    if (*beta == 0.) {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    y[i__] = 0.;
/* L10: */
		}
	    } else {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    y[i__] = *beta * y[i__];
/* L20: */
		}
	    }
	} else {
	    iy = ky;
	    if (*beta == 0.) {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    y[iy] = 0.;
		    iy += *incy;
/* L30: */
		}
	    } else {
		i__1 = *n;
		for (i__ = 1; i__ <= i__1; ++i__) {
		    y[iy] = *beta * y[iy];
		    iy += *incy;
/* L40: */
		}
	    }
	}
    }
    if (*alpha == 0.) {
	return 0;
    }
    if (PASTEF770(lsame)(uplo, "U", (ftnlen)1, (ftnlen)1)) {

/*        Form  y  when upper triangle of A is stored. */

	kplus1 = *k + 1;
	if (*incx == 1 && *incy == 1) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		temp1 = *alpha * x[j];
		temp2 = 0.;
		l = kplus1 - j;
/* Computing MAX */
		i__2 = 1, i__3 = j - *k;
		i__4 = j - 1;
		for (i__ = f2c_max(i__2,i__3); i__ <= i__4; ++i__) {
		    y[i__] += temp1 * a[l + i__ + j * a_dim1];
		    temp2 += a[l + i__ + j * a_dim1] * x[i__];
/* L50: */
		}
		y[j] = y[j] + temp1 * a[kplus1 + j * a_dim1] + *alpha * temp2;
/* L60: */
	    }
	} else {
	    jx = kx;
	    jy = ky;
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		temp1 = *alpha * x[jx];
		temp2 = 0.;
		ix = kx;
		iy = ky;
		l = kplus1 - j;
/* Computing MAX */
		i__4 = 1, i__2 = j - *k;
		i__3 = j - 1;
		for (i__ = f2c_max(i__4,i__2); i__ <= i__3; ++i__) {
		    y[iy] += temp1 * a[l + i__ + j * a_dim1];
		    temp2 += a[l + i__ + j * a_dim1] * x[ix];
		    ix += *incx;
		    iy += *incy;
/* L70: */
		}
		y[jy] = y[jy] + temp1 * a[kplus1 + j * a_dim1] + *alpha * 
			temp2;
		jx += *incx;
		jy += *incy;
		if (j > *k) {
		    kx += *incx;
		    ky += *incy;
		}
/* L80: */
	    }
	}
    } else {

/*        Form  y  when lower triangle of A is stored. */

	if (*incx == 1 && *incy == 1) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		temp1 = *alpha * x[j];
		temp2 = 0.;
		y[j] += temp1 * a[j * a_dim1 + 1];
		l = 1 - j;
/* Computing MIN */
		i__4 = *n, i__2 = j + *k;
		i__3 = f2c_min(i__4,i__2);
		for (i__ = j + 1; i__ <= i__3; ++i__) {
		    y[i__] += temp1 * a[l + i__ + j * a_dim1];
		    temp2 += a[l + i__ + j * a_dim1] * x[i__];
/* L90: */
		}
		y[j] += *alpha * temp2;
/* L100: */
	    }
	} else {
	    jx = kx;
	    jy = ky;
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
		temp1 = *alpha * x[jx];
		temp2 = 0.;
		y[jy] += temp1 * a[j * a_dim1 + 1];
		l = 1 - j;
		ix = jx;
		iy = jy;
/* Computing MIN */
		i__4 = *n, i__2 = j + *k;
		i__3 = f2c_min(i__4,i__2);
		for (i__ = j + 1; i__ <= i__3; ++i__) {
		    ix += *incx;
		    iy += *incy;
		    y[iy] += temp1 * a[l + i__ + j * a_dim1];
		    temp2 += a[l + i__ + j * a_dim1] * x[ix];
/* L110: */
		}
		y[jy] += *alpha * temp2;
		jx += *incx;
		jy += *incy;
/* L120: */
	    }
	}
    }

    return 0;

/*     End of DSBMV . */

} /* dsbmv_ */