| SUBROUTINE CHERF ( UPLO, N, ALPHA, X, INCX, A, LDA ) |
| * .. Scalar Arguments .. |
| REAL ALPHA |
| INTEGER INCX, LDA, N |
| CHARACTER*1 UPLO |
| * .. Array Arguments .. |
| COMPLEX A( LDA, * ), X( * ) |
| * .. |
| * |
| * Purpose |
| * ======= |
| * |
| * CHER performs the hermitian rank 1 operation |
| * |
| * A := alpha*x*conjg( x' ) + A, |
| * |
| * where alpha is a real scalar, x is an n element vector and A is an |
| * n by n hermitian matrix. |
| * |
| * Parameters |
| * ========== |
| * |
| * UPLO - CHARACTER*1. |
| * On entry, UPLO specifies whether the upper or lower |
| * triangular part of the array A is to be referenced as |
| * follows: |
| * |
| * UPLO = 'U' or 'u' Only the upper triangular part of A |
| * is to be referenced. |
| * |
| * UPLO = 'L' or 'l' Only the lower triangular part of A |
| * is to be referenced. |
| * |
| * Unchanged on exit. |
| * |
| * N - INTEGER. |
| * On entry, N specifies the order of the matrix A. |
| * N must be at least zero. |
| * Unchanged on exit. |
| * |
| * ALPHA - REAL . |
| * On entry, ALPHA specifies the scalar alpha. |
| * Unchanged on exit. |
| * |
| * X - COMPLEX array of dimension at least |
| * ( 1 + ( n - 1 )*abs( INCX ) ). |
| * Before entry, the incremented array X must contain the n |
| * element vector x. |
| * Unchanged on exit. |
| * |
| * INCX - INTEGER. |
| * On entry, INCX specifies the increment for the elements of |
| * X. INCX must not be zero. |
| * Unchanged on exit. |
| * |
| * A - COMPLEX array of DIMENSION ( LDA, n ). |
| * Before entry with UPLO = 'U' or 'u', the leading n by n |
| * upper triangular part of the array A must contain the upper |
| * triangular part of the hermitian matrix and the strictly |
| * lower triangular part of A is not referenced. On exit, the |
| * upper triangular part of the array A is overwritten by the |
| * upper triangular part of the updated matrix. |
| * Before entry with UPLO = 'L' or 'l', the leading n by n |
| * lower triangular part of the array A must contain the lower |
| * triangular part of the hermitian matrix and the strictly |
| * upper triangular part of A is not referenced. On exit, the |
| * lower triangular part of the array A is overwritten by the |
| * lower triangular part of the updated matrix. |
| * Note that the imaginary parts of the diagonal elements need |
| * not be set, they are assumed to be zero, and on exit they |
| * are set to zero. |
| * |
| * LDA - INTEGER. |
| * On entry, LDA specifies the first dimension of A as declared |
| * in the calling (sub) program. LDA must be at least |
| * max( 1, n ). |
| * Unchanged on exit. |
| * |
| * |
| * Level 2 Blas routine. |
| * |
| * -- Written on 22-October-1986. |
| * Jack Dongarra, Argonne National Lab. |
| * Jeremy Du Croz, Nag Central Office. |
| * Sven Hammarling, Nag Central Office. |
| * Richard Hanson, Sandia National Labs. |
| * |
| * |
| * .. Parameters .. |
| COMPLEX ZERO |
| PARAMETER ( ZERO = ( 0.0E+0, 0.0E+0 ) ) |
| * .. Local Scalars .. |
| COMPLEX TEMP |
| INTEGER I, INFO, IX, J, JX, KX |
| * .. External Functions .. |
| LOGICAL LSAME |
| EXTERNAL LSAME |
| * .. External Subroutines .. |
| EXTERNAL XERBLA |
| * .. Intrinsic Functions .. |
| INTRINSIC CONJG, MAX, REAL |
| * .. |
| * .. Executable Statements .. |
| * |
| * Test the input parameters. |
| * |
| INFO = 0 |
| IF ( .NOT.LSAME( UPLO, 'U' ).AND. |
| $ .NOT.LSAME( UPLO, 'L' ) )THEN |
| INFO = 1 |
| ELSE IF( N.LT.0 )THEN |
| INFO = 2 |
| ELSE IF( INCX.EQ.0 )THEN |
| INFO = 5 |
| ELSE IF( LDA.LT.MAX( 1, N ) )THEN |
| INFO = 7 |
| END IF |
| IF( INFO.NE.0 )THEN |
| CALL XERBLA( 'CHER ', INFO ) |
| RETURN |
| END IF |
| * |
| * Quick return if possible. |
| * |
| IF( ( N.EQ.0 ).OR.( ALPHA.EQ.REAL( ZERO ) ) ) |
| $ RETURN |
| * |
| * Set the start point in X if the increment is not unity. |
| * |
| IF( INCX.LE.0 )THEN |
| KX = 1 - ( N - 1 )*INCX |
| ELSE IF( INCX.NE.1 )THEN |
| KX = 1 |
| END IF |
| * |
| * Start the operations. In this version the elements of A are |
| * accessed sequentially with one pass through the triangular part |
| * of A. |
| * |
| IF( LSAME( UPLO, 'U' ) )THEN |
| * |
| * Form A when A is stored in upper triangle. |
| * |
| IF( INCX.EQ.1 )THEN |
| DO 20, J = 1, N |
| IF( X( J ).NE.ZERO )THEN |
| TEMP = ALPHA*CONJG( X( J ) ) |
| DO 10, I = 1, J - 1 |
| A( I, J ) = A( I, J ) + X( I )*TEMP |
| 10 CONTINUE |
| A( J, J ) = REAL( A( J, J ) ) + REAL( X( J )*TEMP ) |
| ELSE |
| A( J, J ) = REAL( A( J, J ) ) |
| END IF |
| 20 CONTINUE |
| ELSE |
| JX = KX |
| DO 40, J = 1, N |
| IF( X( JX ).NE.ZERO )THEN |
| TEMP = ALPHA*CONJG( X( JX ) ) |
| IX = KX |
| DO 30, I = 1, J - 1 |
| A( I, J ) = A( I, J ) + X( IX )*TEMP |
| IX = IX + INCX |
| 30 CONTINUE |
| A( J, J ) = REAL( A( J, J ) ) + REAL( X( JX )*TEMP ) |
| ELSE |
| A( J, J ) = REAL( A( J, J ) ) |
| END IF |
| JX = JX + INCX |
| 40 CONTINUE |
| END IF |
| ELSE |
| * |
| * Form A when A is stored in lower triangle. |
| * |
| IF( INCX.EQ.1 )THEN |
| DO 60, J = 1, N |
| IF( X( J ).NE.ZERO )THEN |
| TEMP = ALPHA*CONJG( X( J ) ) |
| A( J, J ) = REAL( A( J, J ) ) + REAL( TEMP*X( J ) ) |
| DO 50, I = J + 1, N |
| A( I, J ) = A( I, J ) + X( I )*TEMP |
| 50 CONTINUE |
| ELSE |
| A( J, J ) = REAL( A( J, J ) ) |
| END IF |
| 60 CONTINUE |
| ELSE |
| JX = KX |
| DO 80, J = 1, N |
| IF( X( JX ).NE.ZERO )THEN |
| TEMP = ALPHA*CONJG( X( JX ) ) |
| A( J, J ) = REAL( A( J, J ) ) + REAL( TEMP*X( JX ) ) |
| IX = JX |
| DO 70, I = J + 1, N |
| IX = IX + INCX |
| A( I, J ) = A( I, J ) + X( IX )*TEMP |
| 70 CONTINUE |
| ELSE |
| A( J, J ) = REAL( A( J, J ) ) |
| END IF |
| JX = JX + INCX |
| 80 CONTINUE |
| END IF |
| END IF |
| * |
| RETURN |
| * |
| * End of CHER . |
| * |
| END |
