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