| SUBROUTINE DGERF ( M, N, ALPHA, X, INCX, Y, INCY, A, LDA ) |
| |
| * .. Scalar Arguments .. |
| DOUBLE PRECISION ALPHA |
| INTEGER INCX, INCY, LDA, M, N |
| * .. Array Arguments .. |
| DOUBLE PRECISION A( LDA, * ), X( * ), Y( * ) |
| * .. |
| * |
| * Purpose |
| * ======= |
| * |
| * DGER performs the rank 1 operation |
| * |
| * A := alpha*x*y' + A, |
| * |
| * where alpha is a scalar, x is an m element vector, y is an n element |
| * vector and A is an m by n matrix. |
| * |
| * Parameters |
| * ========== |
| * |
| * M - INTEGER. |
| * On entry, M specifies the number of rows of the matrix A. |
| * M must be at least zero. |
| * Unchanged on exit. |
| * |
| * N - INTEGER. |
| * On entry, N specifies the number of columns of the matrix A. |
| * N must be at least zero. |
| * Unchanged on exit. |
| * |
| * ALPHA - DOUBLE PRECISION. |
| * On entry, ALPHA specifies the scalar alpha. |
| * Unchanged on exit. |
| * |
| * X - DOUBLE PRECISION array of dimension at least |
| * ( 1 + ( m - 1 )*abs( INCX ) ). |
| * Before entry, the incremented array X must contain the m |
| * 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. |
| * |
| * Y - DOUBLE PRECISION array of dimension at least |
| * ( 1 + ( n - 1 )*abs( INCY ) ). |
| * Before entry, the incremented array Y must contain the n |
| * element vector y. |
| * Unchanged on exit. |
| * |
| * INCY - INTEGER. |
| * On entry, INCY specifies the increment for the elements of |
| * Y. INCY must not be zero. |
| * Unchanged on exit. |
| * |
| * A - DOUBLE PRECISION array of DIMENSION ( LDA, n ). |
| * Before entry, the leading m by n part of the array A must |
| * contain the matrix of coefficients. On exit, A is |
| * overwritten by the updated matrix. |
| * |
| * 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, m ). |
| * 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 .. |
| DOUBLE PRECISION ZERO |
| PARAMETER ( ZERO = 0.0D+0 ) |
| * .. Local Scalars .. |
| DOUBLE PRECISION TEMP |
| INTEGER I, INFO, IX, J, JY, KX |
| * .. External Subroutines .. |
| EXTERNAL XERBLA |
| * .. Intrinsic Functions .. |
| INTRINSIC MAX |
| * .. |
| * .. Executable Statements .. |
| * |
| * Test the input parameters. |
| * |
| INFO = 0 |
| IF ( M.LT.0 )THEN |
| INFO = 1 |
| ELSE IF( N.LT.0 )THEN |
| INFO = 2 |
| ELSE IF( INCX.EQ.0 )THEN |
| INFO = 5 |
| ELSE IF( INCY.EQ.0 )THEN |
| INFO = 7 |
| ELSE IF( LDA.LT.MAX( 1, M ) )THEN |
| INFO = 9 |
| END IF |
| IF( INFO.NE.0 )THEN |
| CALL XERBLA( 'DGER ', INFO ) |
| RETURN |
| END IF |
| * |
| * Quick return if possible. |
| * |
| IF( ( M.EQ.0 ).OR.( N.EQ.0 ).OR.( ALPHA.EQ.ZERO ) ) |
| $ RETURN |
| * |
| * Start the operations. In this version the elements of A are |
| * accessed sequentially with one pass through A. |
| * |
| IF( INCY.GT.0 )THEN |
| JY = 1 |
| ELSE |
| JY = 1 - ( N - 1 )*INCY |
| END IF |
| IF( INCX.EQ.1 )THEN |
| DO 20, J = 1, N |
| IF( Y( JY ).NE.ZERO )THEN |
| TEMP = ALPHA*Y( JY ) |
| DO 10, I = 1, M |
| A( I, J ) = A( I, J ) + X( I )*TEMP |
| 10 CONTINUE |
| END IF |
| JY = JY + INCY |
| 20 CONTINUE |
| ELSE |
| IF( INCX.GT.0 )THEN |
| KX = 1 |
| ELSE |
| KX = 1 - ( M - 1 )*INCX |
| END IF |
| DO 40, J = 1, N |
| IF( Y( JY ).NE.ZERO )THEN |
| TEMP = ALPHA*Y( JY ) |
| IX = KX |
| DO 30, I = 1, M |
| A( I, J ) = A( I, J ) + X( IX )*TEMP |
| IX = IX + INCX |
| 30 CONTINUE |
| END IF |
| JY = JY + INCY |
| 40 CONTINUE |
| END IF |
| * |
| RETURN |
| * |
| * End of DGER . |
| * |
| END |
