Annotation of rpl/lapack/blas/zher.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE ZHER(UPLO,N,ALPHA,X,INCX,A,LDA)
! 2: * .. Scalar Arguments ..
! 3: DOUBLE PRECISION ALPHA
! 4: INTEGER INCX,LDA,N
! 5: CHARACTER UPLO
! 6: * ..
! 7: * .. Array Arguments ..
! 8: DOUBLE COMPLEX A(LDA,*),X(*)
! 9: * ..
! 10: *
! 11: * Purpose
! 12: * =======
! 13: *
! 14: * ZHER performs the hermitian rank 1 operation
! 15: *
! 16: * A := alpha*x*conjg( x' ) + A,
! 17: *
! 18: * where alpha is a real scalar, x is an n element vector and A is an
! 19: * n by n hermitian matrix.
! 20: *
! 21: * Arguments
! 22: * ==========
! 23: *
! 24: * UPLO - CHARACTER*1.
! 25: * On entry, UPLO specifies whether the upper or lower
! 26: * triangular part of the array A is to be referenced as
! 27: * follows:
! 28: *
! 29: * UPLO = 'U' or 'u' Only the upper triangular part of A
! 30: * is to be referenced.
! 31: *
! 32: * UPLO = 'L' or 'l' Only the lower triangular part of A
! 33: * is to be referenced.
! 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 - COMPLEX*16 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: * A - COMPLEX*16 array of DIMENSION ( LDA, n ).
! 58: * Before entry with UPLO = 'U' or 'u', the leading n by n
! 59: * upper triangular part of the array A must contain the upper
! 60: * triangular part of the hermitian matrix and the strictly
! 61: * lower triangular part of A is not referenced. On exit, the
! 62: * upper triangular part of the array A is overwritten by the
! 63: * upper triangular part of the updated matrix.
! 64: * Before entry with UPLO = 'L' or 'l', the leading n by n
! 65: * lower triangular part of the array A must contain the lower
! 66: * triangular part of the hermitian matrix and the strictly
! 67: * upper triangular part of A is not referenced. On exit, the
! 68: * lower triangular part of the array A is overwritten by the
! 69: * lower triangular part of the updated matrix.
! 70: * Note that the imaginary parts of the diagonal elements need
! 71: * not be set, they are assumed to be zero, and on exit they
! 72: * are set to zero.
! 73: *
! 74: * LDA - INTEGER.
! 75: * On entry, LDA specifies the first dimension of A as declared
! 76: * in the calling (sub) program. LDA must be at least
! 77: * max( 1, n ).
! 78: * Unchanged on exit.
! 79: *
! 80: * Further Details
! 81: * ===============
! 82: *
! 83: * Level 2 Blas routine.
! 84: *
! 85: * -- Written on 22-October-1986.
! 86: * Jack Dongarra, Argonne National Lab.
! 87: * Jeremy Du Croz, Nag Central Office.
! 88: * Sven Hammarling, Nag Central Office.
! 89: * Richard Hanson, Sandia National Labs.
! 90: *
! 91: * =====================================================================
! 92: *
! 93: * .. Parameters ..
! 94: DOUBLE COMPLEX ZERO
! 95: PARAMETER (ZERO= (0.0D+0,0.0D+0))
! 96: * ..
! 97: * .. Local Scalars ..
! 98: DOUBLE COMPLEX TEMP
! 99: INTEGER I,INFO,IX,J,JX,KX
! 100: * ..
! 101: * .. External Functions ..
! 102: LOGICAL LSAME
! 103: EXTERNAL LSAME
! 104: * ..
! 105: * .. External Subroutines ..
! 106: EXTERNAL XERBLA
! 107: * ..
! 108: * .. Intrinsic Functions ..
! 109: INTRINSIC DBLE,DCONJG,MAX
! 110: * ..
! 111: *
! 112: * Test the input parameters.
! 113: *
! 114: INFO = 0
! 115: IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN
! 116: INFO = 1
! 117: ELSE IF (N.LT.0) THEN
! 118: INFO = 2
! 119: ELSE IF (INCX.EQ.0) THEN
! 120: INFO = 5
! 121: ELSE IF (LDA.LT.MAX(1,N)) THEN
! 122: INFO = 7
! 123: END IF
! 124: IF (INFO.NE.0) THEN
! 125: CALL XERBLA('ZHER ',INFO)
! 126: RETURN
! 127: END IF
! 128: *
! 129: * Quick return if possible.
! 130: *
! 131: IF ((N.EQ.0) .OR. (ALPHA.EQ.DBLE(ZERO))) RETURN
! 132: *
! 133: * Set the start point in X if the increment is not unity.
! 134: *
! 135: IF (INCX.LE.0) THEN
! 136: KX = 1 - (N-1)*INCX
! 137: ELSE IF (INCX.NE.1) THEN
! 138: KX = 1
! 139: END IF
! 140: *
! 141: * Start the operations. In this version the elements of A are
! 142: * accessed sequentially with one pass through the triangular part
! 143: * of A.
! 144: *
! 145: IF (LSAME(UPLO,'U')) THEN
! 146: *
! 147: * Form A when A is stored in upper triangle.
! 148: *
! 149: IF (INCX.EQ.1) THEN
! 150: DO 20 J = 1,N
! 151: IF (X(J).NE.ZERO) THEN
! 152: TEMP = ALPHA*DCONJG(X(J))
! 153: DO 10 I = 1,J - 1
! 154: A(I,J) = A(I,J) + X(I)*TEMP
! 155: 10 CONTINUE
! 156: A(J,J) = DBLE(A(J,J)) + DBLE(X(J)*TEMP)
! 157: ELSE
! 158: A(J,J) = DBLE(A(J,J))
! 159: END IF
! 160: 20 CONTINUE
! 161: ELSE
! 162: JX = KX
! 163: DO 40 J = 1,N
! 164: IF (X(JX).NE.ZERO) THEN
! 165: TEMP = ALPHA*DCONJG(X(JX))
! 166: IX = KX
! 167: DO 30 I = 1,J - 1
! 168: A(I,J) = A(I,J) + X(IX)*TEMP
! 169: IX = IX + INCX
! 170: 30 CONTINUE
! 171: A(J,J) = DBLE(A(J,J)) + DBLE(X(JX)*TEMP)
! 172: ELSE
! 173: A(J,J) = DBLE(A(J,J))
! 174: END IF
! 175: JX = JX + INCX
! 176: 40 CONTINUE
! 177: END IF
! 178: ELSE
! 179: *
! 180: * Form A when A is stored in lower triangle.
! 181: *
! 182: IF (INCX.EQ.1) THEN
! 183: DO 60 J = 1,N
! 184: IF (X(J).NE.ZERO) THEN
! 185: TEMP = ALPHA*DCONJG(X(J))
! 186: A(J,J) = DBLE(A(J,J)) + DBLE(TEMP*X(J))
! 187: DO 50 I = J + 1,N
! 188: A(I,J) = A(I,J) + X(I)*TEMP
! 189: 50 CONTINUE
! 190: ELSE
! 191: A(J,J) = DBLE(A(J,J))
! 192: END IF
! 193: 60 CONTINUE
! 194: ELSE
! 195: JX = KX
! 196: DO 80 J = 1,N
! 197: IF (X(JX).NE.ZERO) THEN
! 198: TEMP = ALPHA*DCONJG(X(JX))
! 199: A(J,J) = DBLE(A(J,J)) + DBLE(TEMP*X(JX))
! 200: IX = JX
! 201: DO 70 I = J + 1,N
! 202: IX = IX + INCX
! 203: A(I,J) = A(I,J) + X(IX)*TEMP
! 204: 70 CONTINUE
! 205: ELSE
! 206: A(J,J) = DBLE(A(J,J))
! 207: END IF
! 208: JX = JX + INCX
! 209: 80 CONTINUE
! 210: END IF
! 211: END IF
! 212: *
! 213: RETURN
! 214: *
! 215: * End of ZHER .
! 216: *
! 217: END
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