Annotation of rpl/lapack/blas/zher2.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE ZHER2(UPLO,N,ALPHA,X,INCX,Y,INCY,A,LDA)
! 2: * .. Scalar Arguments ..
! 3: DOUBLE COMPLEX ALPHA
! 4: INTEGER INCX,INCY,LDA,N
! 5: CHARACTER UPLO
! 6: * ..
! 7: * .. Array Arguments ..
! 8: DOUBLE COMPLEX A(LDA,*),X(*),Y(*)
! 9: * ..
! 10: *
! 11: * Purpose
! 12: * =======
! 13: *
! 14: * ZHER2 performs the hermitian rank 2 operation
! 15: *
! 16: * A := alpha*x*conjg( y' ) + conjg( alpha )*y*conjg( x' ) + A,
! 17: *
! 18: * where alpha is a scalar, x and y are n element vectors and A is an n
! 19: * 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 - COMPLEX*16 .
! 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: * Y - COMPLEX*16 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: * A - COMPLEX*16 array of DIMENSION ( LDA, n ).
! 69: * Before entry with UPLO = 'U' or 'u', the leading n by n
! 70: * upper triangular part of the array A must contain the upper
! 71: * triangular part of the hermitian matrix and the strictly
! 72: * lower triangular part of A is not referenced. On exit, the
! 73: * upper triangular part of the array A is overwritten by the
! 74: * upper triangular part of the updated matrix.
! 75: * Before entry with UPLO = 'L' or 'l', the leading n by n
! 76: * lower triangular part of the array A must contain the lower
! 77: * triangular part of the hermitian matrix and the strictly
! 78: * upper triangular part of A is not referenced. On exit, the
! 79: * lower triangular part of the array A is overwritten by the
! 80: * lower triangular part of the updated matrix.
! 81: * Note that the imaginary parts of the diagonal elements need
! 82: * not be set, they are assumed to be zero, and on exit they
! 83: * are set to zero.
! 84: *
! 85: * LDA - INTEGER.
! 86: * On entry, LDA specifies the first dimension of A as declared
! 87: * in the calling (sub) program. LDA must be at least
! 88: * max( 1, n ).
! 89: * Unchanged on exit.
! 90: *
! 91: * Further Details
! 92: * ===============
! 93: *
! 94: * Level 2 Blas routine.
! 95: *
! 96: * -- Written on 22-October-1986.
! 97: * Jack Dongarra, Argonne National Lab.
! 98: * Jeremy Du Croz, Nag Central Office.
! 99: * Sven Hammarling, Nag Central Office.
! 100: * Richard Hanson, Sandia National Labs.
! 101: *
! 102: * =====================================================================
! 103: *
! 104: * .. Parameters ..
! 105: DOUBLE COMPLEX ZERO
! 106: PARAMETER (ZERO= (0.0D+0,0.0D+0))
! 107: * ..
! 108: * .. Local Scalars ..
! 109: DOUBLE COMPLEX TEMP1,TEMP2
! 110: INTEGER I,INFO,IX,IY,J,JX,JY,KX,KY
! 111: * ..
! 112: * .. External Functions ..
! 113: LOGICAL LSAME
! 114: EXTERNAL LSAME
! 115: * ..
! 116: * .. External Subroutines ..
! 117: EXTERNAL XERBLA
! 118: * ..
! 119: * .. Intrinsic Functions ..
! 120: INTRINSIC DBLE,DCONJG,MAX
! 121: * ..
! 122: *
! 123: * Test the input parameters.
! 124: *
! 125: INFO = 0
! 126: IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN
! 127: INFO = 1
! 128: ELSE IF (N.LT.0) THEN
! 129: INFO = 2
! 130: ELSE IF (INCX.EQ.0) THEN
! 131: INFO = 5
! 132: ELSE IF (INCY.EQ.0) THEN
! 133: INFO = 7
! 134: ELSE IF (LDA.LT.MAX(1,N)) THEN
! 135: INFO = 9
! 136: END IF
! 137: IF (INFO.NE.0) THEN
! 138: CALL XERBLA('ZHER2 ',INFO)
! 139: RETURN
! 140: END IF
! 141: *
! 142: * Quick return if possible.
! 143: *
! 144: IF ((N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN
! 145: *
! 146: * Set up the start points in X and Y if the increments are not both
! 147: * unity.
! 148: *
! 149: IF ((INCX.NE.1) .OR. (INCY.NE.1)) THEN
! 150: IF (INCX.GT.0) THEN
! 151: KX = 1
! 152: ELSE
! 153: KX = 1 - (N-1)*INCX
! 154: END IF
! 155: IF (INCY.GT.0) THEN
! 156: KY = 1
! 157: ELSE
! 158: KY = 1 - (N-1)*INCY
! 159: END IF
! 160: JX = KX
! 161: JY = KY
! 162: END IF
! 163: *
! 164: * Start the operations. In this version the elements of A are
! 165: * accessed sequentially with one pass through the triangular part
! 166: * of A.
! 167: *
! 168: IF (LSAME(UPLO,'U')) THEN
! 169: *
! 170: * Form A when A is stored in the upper triangle.
! 171: *
! 172: IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
! 173: DO 20 J = 1,N
! 174: IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN
! 175: TEMP1 = ALPHA*DCONJG(Y(J))
! 176: TEMP2 = DCONJG(ALPHA*X(J))
! 177: DO 10 I = 1,J - 1
! 178: A(I,J) = A(I,J) + X(I)*TEMP1 + Y(I)*TEMP2
! 179: 10 CONTINUE
! 180: A(J,J) = DBLE(A(J,J)) +
! 181: + DBLE(X(J)*TEMP1+Y(J)*TEMP2)
! 182: ELSE
! 183: A(J,J) = DBLE(A(J,J))
! 184: END IF
! 185: 20 CONTINUE
! 186: ELSE
! 187: DO 40 J = 1,N
! 188: IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN
! 189: TEMP1 = ALPHA*DCONJG(Y(JY))
! 190: TEMP2 = DCONJG(ALPHA*X(JX))
! 191: IX = KX
! 192: IY = KY
! 193: DO 30 I = 1,J - 1
! 194: A(I,J) = A(I,J) + X(IX)*TEMP1 + Y(IY)*TEMP2
! 195: IX = IX + INCX
! 196: IY = IY + INCY
! 197: 30 CONTINUE
! 198: A(J,J) = DBLE(A(J,J)) +
! 199: + DBLE(X(JX)*TEMP1+Y(JY)*TEMP2)
! 200: ELSE
! 201: A(J,J) = DBLE(A(J,J))
! 202: END IF
! 203: JX = JX + INCX
! 204: JY = JY + INCY
! 205: 40 CONTINUE
! 206: END IF
! 207: ELSE
! 208: *
! 209: * Form A when A is stored in the lower triangle.
! 210: *
! 211: IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN
! 212: DO 60 J = 1,N
! 213: IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN
! 214: TEMP1 = ALPHA*DCONJG(Y(J))
! 215: TEMP2 = DCONJG(ALPHA*X(J))
! 216: A(J,J) = DBLE(A(J,J)) +
! 217: + DBLE(X(J)*TEMP1+Y(J)*TEMP2)
! 218: DO 50 I = J + 1,N
! 219: A(I,J) = A(I,J) + X(I)*TEMP1 + Y(I)*TEMP2
! 220: 50 CONTINUE
! 221: ELSE
! 222: A(J,J) = DBLE(A(J,J))
! 223: END IF
! 224: 60 CONTINUE
! 225: ELSE
! 226: DO 80 J = 1,N
! 227: IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN
! 228: TEMP1 = ALPHA*DCONJG(Y(JY))
! 229: TEMP2 = DCONJG(ALPHA*X(JX))
! 230: A(J,J) = DBLE(A(J,J)) +
! 231: + DBLE(X(JX)*TEMP1+Y(JY)*TEMP2)
! 232: IX = JX
! 233: IY = JY
! 234: DO 70 I = J + 1,N
! 235: IX = IX + INCX
! 236: IY = IY + INCY
! 237: A(I,J) = A(I,J) + X(IX)*TEMP1 + Y(IY)*TEMP2
! 238: 70 CONTINUE
! 239: ELSE
! 240: A(J,J) = DBLE(A(J,J))
! 241: END IF
! 242: JX = JX + INCX
! 243: JY = JY + INCY
! 244: 80 CONTINUE
! 245: END IF
! 246: END IF
! 247: *
! 248: RETURN
! 249: *
! 250: * End of ZHER2 .
! 251: *
! 252: END
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