Annotation of rpl/lapack/blas/dspmv.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DSPMV(UPLO,N,ALPHA,AP,X,INCX,BETA,Y,INCY)
! 2: * .. Scalar Arguments ..
! 3: DOUBLE PRECISION ALPHA,BETA
! 4: INTEGER INCX,INCY,N
! 5: CHARACTER UPLO
! 6: * ..
! 7: * .. Array Arguments ..
! 8: DOUBLE PRECISION AP(*),X(*),Y(*)
! 9: * ..
! 10: *
! 11: * Purpose
! 12: * =======
! 13: *
! 14: * DSPMV performs the matrix-vector operation
! 15: *
! 16: * y := alpha*A*x + beta*y,
! 17: *
! 18: * where alpha and beta are scalars, x and y are n element vectors and
! 19: * A is an n by n symmetric matrix, supplied in packed form.
! 20: *
! 21: * Arguments
! 22: * ==========
! 23: *
! 24: * UPLO - CHARACTER*1.
! 25: * On entry, UPLO specifies whether the upper or lower
! 26: * triangular part of the matrix A is supplied in the packed
! 27: * array AP as follows:
! 28: *
! 29: * UPLO = 'U' or 'u' The upper triangular part of A is
! 30: * supplied in AP.
! 31: *
! 32: * UPLO = 'L' or 'l' The lower triangular part of A is
! 33: * supplied in AP.
! 34: *
! 35: * Unchanged on exit.
! 36: *
! 37: * N - INTEGER.
! 38: * On entry, N specifies the order of the matrix A.
! 39: * N must be at least zero.
! 40: * Unchanged on exit.
! 41: *
! 42: * ALPHA - DOUBLE PRECISION.
! 43: * On entry, ALPHA specifies the scalar alpha.
! 44: * Unchanged on exit.
! 45: *
! 46: * AP - DOUBLE PRECISION array of DIMENSION at least
! 47: * ( ( n*( n + 1 ) )/2 ).
! 48: * Before entry with UPLO = 'U' or 'u', the array AP must
! 49: * contain the upper triangular part of the symmetric matrix
! 50: * packed sequentially, column by column, so that AP( 1 )
! 51: * contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )
! 52: * and a( 2, 2 ) respectively, and so on.
! 53: * Before entry with UPLO = 'L' or 'l', the array AP must
! 54: * contain the lower triangular part of the symmetric matrix
! 55: * packed sequentially, column by column, so that AP( 1 )
! 56: * contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )
! 57: * and a( 3, 1 ) respectively, and so on.
! 58: * Unchanged on exit.
! 59: *
! 60: * X - DOUBLE PRECISION array of dimension at least
! 61: * ( 1 + ( n - 1 )*abs( INCX ) ).
! 62: * Before entry, the incremented array X must contain the n
! 63: * element vector x.
! 64: * Unchanged on exit.
! 65: *
! 66: * INCX - INTEGER.
! 67: * On entry, INCX specifies the increment for the elements of
! 68: * X. INCX must not be zero.
! 69: * Unchanged on exit.
! 70: *
! 71: * BETA - DOUBLE PRECISION.
! 72: * On entry, BETA specifies the scalar beta. When BETA is
! 73: * supplied as zero then Y need not be set on input.
! 74: * Unchanged on exit.
! 75: *
! 76: * Y - DOUBLE PRECISION array of dimension at least
! 77: * ( 1 + ( n - 1 )*abs( INCY ) ).
! 78: * Before entry, the incremented array Y must contain the n
! 79: * element vector y. On exit, Y is overwritten by the updated
! 80: * vector y.
! 81: *
! 82: * INCY - INTEGER.
! 83: * On entry, INCY specifies the increment for the elements of
! 84: * Y. INCY must not be zero.
! 85: * Unchanged on exit.
! 86: *
! 87: * Further Details
! 88: * ===============
! 89: *
! 90: * Level 2 Blas routine.
! 91: *
! 92: * -- Written on 22-October-1986.
! 93: * Jack Dongarra, Argonne National Lab.
! 94: * Jeremy Du Croz, Nag Central Office.
! 95: * Sven Hammarling, Nag Central Office.
! 96: * Richard Hanson, Sandia National Labs.
! 97: *
! 98: * =====================================================================
! 99: *
! 100: * .. Parameters ..
! 101: DOUBLE PRECISION ONE,ZERO
! 102: PARAMETER (ONE=1.0D+0,ZERO=0.0D+0)
! 103: * ..
! 104: * .. Local Scalars ..
! 105: DOUBLE PRECISION TEMP1,TEMP2
! 106: INTEGER I,INFO,IX,IY,J,JX,JY,K,KK,KX,KY
! 107: * ..
! 108: * .. External Functions ..
! 109: LOGICAL LSAME
! 110: EXTERNAL LSAME
! 111: * ..
! 112: * .. External Subroutines ..
! 113: EXTERNAL XERBLA
! 114: * ..
! 115: *
! 116: * Test the input parameters.
! 117: *
! 118: INFO = 0
! 119: IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN
! 120: INFO = 1
! 121: ELSE IF (N.LT.0) THEN
! 122: INFO = 2
! 123: ELSE IF (INCX.EQ.0) THEN
! 124: INFO = 6
! 125: ELSE IF (INCY.EQ.0) THEN
! 126: INFO = 9
! 127: END IF
! 128: IF (INFO.NE.0) THEN
! 129: CALL XERBLA('DSPMV ',INFO)
! 130: RETURN
! 131: END IF
! 132: *
! 133: * Quick return if possible.
! 134: *
! 135: IF ((N.EQ.0) .OR. ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN
! 136: *
! 137: * Set up the start points in X and Y.
! 138: *
! 139: IF (INCX.GT.0) THEN
! 140: KX = 1
! 141: ELSE
! 142: KX = 1 - (N-1)*INCX
! 143: END IF
! 144: IF (INCY.GT.0) THEN
! 145: KY = 1
! 146: ELSE
! 147: KY = 1 - (N-1)*INCY
! 148: END IF
! 149: *
! 150: * Start the operations. In this version the elements of the array AP
! 151: * are accessed sequentially with one pass through AP.
! 152: *
! 153: * First form y := beta*y.
! 154: *
! 155: IF (BETA.NE.ONE) THEN
! 156: IF (INCY.EQ.1) THEN
! 157: IF (BETA.EQ.ZERO) THEN
! 158: DO 10 I = 1,N
! 159: Y(I) = ZERO
! 160: 10 CONTINUE
! 161: ELSE
! 162: DO 20 I = 1,N
! 163: Y(I) = BETA*Y(I)
! 164: 20 CONTINUE
! 165: END IF
! 166: ELSE
! 167: IY = KY
! 168: IF (BETA.EQ.ZERO) THEN
! 169: DO 30 I = 1,N
! 170: Y(IY) = ZERO
! 171: IY = IY + INCY
! 172: 30 CONTINUE
! 173: ELSE
! 174: DO 40 I = 1,N
! 175: Y(IY) = BETA*Y(IY)
! 176: IY = IY + INCY
! 177: 40 CONTINUE
! 178: END IF
! 179: END IF
! 180: END IF
! 181: IF (ALPHA.EQ.ZERO) RETURN
! 182: KK = 1
! 183: IF (LSAME(UPLO,'U')) THEN
! 184: *
! 185: * Form y when AP contains the upper triangle.
! 186: *
! 187: IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
! 188: DO 60 J = 1,N
! 189: TEMP1 = ALPHA*X(J)
! 190: TEMP2 = ZERO
! 191: K = KK
! 192: DO 50 I = 1,J - 1
! 193: Y(I) = Y(I) + TEMP1*AP(K)
! 194: TEMP2 = TEMP2 + AP(K)*X(I)
! 195: K = K + 1
! 196: 50 CONTINUE
! 197: Y(J) = Y(J) + TEMP1*AP(KK+J-1) + ALPHA*TEMP2
! 198: KK = KK + J
! 199: 60 CONTINUE
! 200: ELSE
! 201: JX = KX
! 202: JY = KY
! 203: DO 80 J = 1,N
! 204: TEMP1 = ALPHA*X(JX)
! 205: TEMP2 = ZERO
! 206: IX = KX
! 207: IY = KY
! 208: DO 70 K = KK,KK + J - 2
! 209: Y(IY) = Y(IY) + TEMP1*AP(K)
! 210: TEMP2 = TEMP2 + AP(K)*X(IX)
! 211: IX = IX + INCX
! 212: IY = IY + INCY
! 213: 70 CONTINUE
! 214: Y(JY) = Y(JY) + TEMP1*AP(KK+J-1) + ALPHA*TEMP2
! 215: JX = JX + INCX
! 216: JY = JY + INCY
! 217: KK = KK + J
! 218: 80 CONTINUE
! 219: END IF
! 220: ELSE
! 221: *
! 222: * Form y when AP contains the lower triangle.
! 223: *
! 224: IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
! 225: DO 100 J = 1,N
! 226: TEMP1 = ALPHA*X(J)
! 227: TEMP2 = ZERO
! 228: Y(J) = Y(J) + TEMP1*AP(KK)
! 229: K = KK + 1
! 230: DO 90 I = J + 1,N
! 231: Y(I) = Y(I) + TEMP1*AP(K)
! 232: TEMP2 = TEMP2 + AP(K)*X(I)
! 233: K = K + 1
! 234: 90 CONTINUE
! 235: Y(J) = Y(J) + ALPHA*TEMP2
! 236: KK = KK + (N-J+1)
! 237: 100 CONTINUE
! 238: ELSE
! 239: JX = KX
! 240: JY = KY
! 241: DO 120 J = 1,N
! 242: TEMP1 = ALPHA*X(JX)
! 243: TEMP2 = ZERO
! 244: Y(JY) = Y(JY) + TEMP1*AP(KK)
! 245: IX = JX
! 246: IY = JY
! 247: DO 110 K = KK + 1,KK + N - J
! 248: IX = IX + INCX
! 249: IY = IY + INCY
! 250: Y(IY) = Y(IY) + TEMP1*AP(K)
! 251: TEMP2 = TEMP2 + AP(K)*X(IX)
! 252: 110 CONTINUE
! 253: Y(JY) = Y(JY) + ALPHA*TEMP2
! 254: JX = JX + INCX
! 255: JY = JY + INCY
! 256: KK = KK + (N-J+1)
! 257: 120 CONTINUE
! 258: END IF
! 259: END IF
! 260: *
! 261: RETURN
! 262: *
! 263: * End of DSPMV .
! 264: *
! 265: END
CVSweb interface <joel.bertrand@systella.fr>
![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to dspmv.f CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [local] / rpl / lapack / blas