Annotation of rpl/lapack/blas/dspr2.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DSPR2(UPLO,N,ALPHA,X,INCX,Y,INCY,AP)
! 2: * .. Scalar Arguments ..
! 3: DOUBLE PRECISION ALPHA
! 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: * DSPR2 performs the symmetric rank 2 operation
! 15: *
! 16: * A := alpha*x*y' + alpha*y*x' + A,
! 17: *
! 18: * where alpha is a scalar, x and y are n element vectors and A is an
! 19: * 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: * X - DOUBLE PRECISION array of dimension at least
! 47: * ( 1 + ( n - 1 )*abs( INCX ) ).
! 48: * Before entry, the incremented array X must contain the n
! 49: * element vector x.
! 50: * Unchanged on exit.
! 51: *
! 52: * INCX - INTEGER.
! 53: * On entry, INCX specifies the increment for the elements of
! 54: * X. INCX must not be zero.
! 55: * Unchanged on exit.
! 56: *
! 57: * Y - DOUBLE PRECISION array of dimension at least
! 58: * ( 1 + ( n - 1 )*abs( INCY ) ).
! 59: * Before entry, the incremented array Y must contain the n
! 60: * element vector y.
! 61: * Unchanged on exit.
! 62: *
! 63: * INCY - INTEGER.
! 64: * On entry, INCY specifies the increment for the elements of
! 65: * Y. INCY must not be zero.
! 66: * Unchanged on exit.
! 67: *
! 68: * AP - DOUBLE PRECISION array of DIMENSION at least
! 69: * ( ( n*( n + 1 ) )/2 ).
! 70: * Before entry with UPLO = 'U' or 'u', the array AP must
! 71: * contain the upper triangular part of the symmetric matrix
! 72: * packed sequentially, column by column, so that AP( 1 )
! 73: * contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )
! 74: * and a( 2, 2 ) respectively, and so on. On exit, the array
! 75: * AP is overwritten by the upper triangular part of the
! 76: * updated matrix.
! 77: * Before entry with UPLO = 'L' or 'l', the array AP must
! 78: * contain the lower triangular part of the symmetric matrix
! 79: * packed sequentially, column by column, so that AP( 1 )
! 80: * contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )
! 81: * and a( 3, 1 ) respectively, and so on. On exit, the array
! 82: * AP is overwritten by the lower triangular part of the
! 83: * updated matrix.
! 84: *
! 85: * Further Details
! 86: * ===============
! 87: *
! 88: * Level 2 Blas routine.
! 89: *
! 90: * -- Written on 22-October-1986.
! 91: * Jack Dongarra, Argonne National Lab.
! 92: * Jeremy Du Croz, Nag Central Office.
! 93: * Sven Hammarling, Nag Central Office.
! 94: * Richard Hanson, Sandia National Labs.
! 95: *
! 96: * =====================================================================
! 97: *
! 98: * .. Parameters ..
! 99: DOUBLE PRECISION ZERO
! 100: PARAMETER (ZERO=0.0D+0)
! 101: * ..
! 102: * .. Local Scalars ..
! 103: DOUBLE PRECISION TEMP1,TEMP2
! 104: INTEGER I,INFO,IX,IY,J,JX,JY,K,KK,KX,KY
! 105: * ..
! 106: * .. External Functions ..
! 107: LOGICAL LSAME
! 108: EXTERNAL LSAME
! 109: * ..
! 110: * .. External Subroutines ..
! 111: EXTERNAL XERBLA
! 112: * ..
! 113: *
! 114: * Test the input parameters.
! 115: *
! 116: INFO = 0
! 117: IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN
! 118: INFO = 1
! 119: ELSE IF (N.LT.0) THEN
! 120: INFO = 2
! 121: ELSE IF (INCX.EQ.0) THEN
! 122: INFO = 5
! 123: ELSE IF (INCY.EQ.0) THEN
! 124: INFO = 7
! 125: END IF
! 126: IF (INFO.NE.0) THEN
! 127: CALL XERBLA('DSPR2 ',INFO)
! 128: RETURN
! 129: END IF
! 130: *
! 131: * Quick return if possible.
! 132: *
! 133: IF ((N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN
! 134: *
! 135: * Set up the start points in X and Y if the increments are not both
! 136: * unity.
! 137: *
! 138: IF ((INCX.NE.1) .OR. (INCY.NE.1)) THEN
! 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: JX = KX
! 150: JY = KY
! 151: END IF
! 152: *
! 153: * Start the operations. In this version the elements of the array AP
! 154: * are accessed sequentially with one pass through AP.
! 155: *
! 156: KK = 1
! 157: IF (LSAME(UPLO,'U')) THEN
! 158: *
! 159: * Form A when upper triangle is stored in AP.
! 160: *
! 161: IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
! 162: DO 20 J = 1,N
! 163: IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN
! 164: TEMP1 = ALPHA*Y(J)
! 165: TEMP2 = ALPHA*X(J)
! 166: K = KK
! 167: DO 10 I = 1,J
! 168: AP(K) = AP(K) + X(I)*TEMP1 + Y(I)*TEMP2
! 169: K = K + 1
! 170: 10 CONTINUE
! 171: END IF
! 172: KK = KK + J
! 173: 20 CONTINUE
! 174: ELSE
! 175: DO 40 J = 1,N
! 176: IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN
! 177: TEMP1 = ALPHA*Y(JY)
! 178: TEMP2 = ALPHA*X(JX)
! 179: IX = KX
! 180: IY = KY
! 181: DO 30 K = KK,KK + J - 1
! 182: AP(K) = AP(K) + X(IX)*TEMP1 + Y(IY)*TEMP2
! 183: IX = IX + INCX
! 184: IY = IY + INCY
! 185: 30 CONTINUE
! 186: END IF
! 187: JX = JX + INCX
! 188: JY = JY + INCY
! 189: KK = KK + J
! 190: 40 CONTINUE
! 191: END IF
! 192: ELSE
! 193: *
! 194: * Form A when lower triangle is stored in AP.
! 195: *
! 196: IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
! 197: DO 60 J = 1,N
! 198: IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN
! 199: TEMP1 = ALPHA*Y(J)
! 200: TEMP2 = ALPHA*X(J)
! 201: K = KK
! 202: DO 50 I = J,N
! 203: AP(K) = AP(K) + X(I)*TEMP1 + Y(I)*TEMP2
! 204: K = K + 1
! 205: 50 CONTINUE
! 206: END IF
! 207: KK = KK + N - J + 1
! 208: 60 CONTINUE
! 209: ELSE
! 210: DO 80 J = 1,N
! 211: IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN
! 212: TEMP1 = ALPHA*Y(JY)
! 213: TEMP2 = ALPHA*X(JX)
! 214: IX = JX
! 215: IY = JY
! 216: DO 70 K = KK,KK + N - J
! 217: AP(K) = AP(K) + X(IX)*TEMP1 + Y(IY)*TEMP2
! 218: IX = IX + INCX
! 219: IY = IY + INCY
! 220: 70 CONTINUE
! 221: END IF
! 222: JX = JX + INCX
! 223: JY = JY + INCY
! 224: KK = KK + N - J + 1
! 225: 80 CONTINUE
! 226: END IF
! 227: END IF
! 228: *
! 229: RETURN
! 230: *
! 231: * End of DSPR2 .
! 232: *
! 233: END
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