SUBROUTINE ZGET03( N, A, LDA, AINV, LDAINV, WORK, LDWORK, RWORK, \$ RCOND, RESID ) * * -- LAPACK test routine (version 3.1) -- * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. * November 2006 * * .. Scalar Arguments .. INTEGER LDA, LDAINV, LDWORK, N DOUBLE PRECISION RCOND, RESID * .. * .. Array Arguments .. DOUBLE PRECISION RWORK( * ) COMPLEX*16 A( LDA, * ), AINV( LDAINV, * ), \$ WORK( LDWORK, * ) * .. * * Purpose * ======= * * ZGET03 computes the residual for a general matrix times its inverse: * norm( I - AINV*A ) / ( N * norm(A) * norm(AINV) * EPS ), * where EPS is the machine epsilon. * * Arguments * ========== * * N (input) INTEGER * The number of rows and columns of the matrix A. N >= 0. * * A (input) COMPLEX*16 array, dimension (LDA,N) * The original N x N matrix A. * * LDA (input) INTEGER * The leading dimension of the array A. LDA >= max(1,N). * * AINV (input) COMPLEX*16 array, dimension (LDAINV,N) * The inverse of the matrix A. * * LDAINV (input) INTEGER * The leading dimension of the array AINV. LDAINV >= max(1,N). * * WORK (workspace) COMPLEX*16 array, dimension (LDWORK,N) * * LDWORK (input) INTEGER * The leading dimension of the array WORK. LDWORK >= max(1,N). * * RWORK (workspace) DOUBLE PRECISION array, dimension (N) * * RCOND (output) DOUBLE PRECISION * The reciprocal of the condition number of A, computed as * ( 1/norm(A) ) / norm(AINV). * * RESID (output) DOUBLE PRECISION * norm(I - AINV*A) / ( N * norm(A) * norm(AINV) * EPS ) * * ===================================================================== * * .. Parameters .. DOUBLE PRECISION ZERO, ONE PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 ) COMPLEX*16 CZERO, CONE PARAMETER ( CZERO = ( 0.0D+0, 0.0D+0 ), \$ CONE = ( 1.0D+0, 0.0D+0 ) ) * .. * .. Local Scalars .. INTEGER I DOUBLE PRECISION AINVNM, ANORM, EPS * .. * .. External Functions .. DOUBLE PRECISION DLAMCH, ZLANGE EXTERNAL DLAMCH, ZLANGE * .. * .. External Subroutines .. EXTERNAL ZGEMM * .. * .. Intrinsic Functions .. INTRINSIC DBLE * .. * .. Executable Statements .. * * Quick exit if N = 0. * IF( N.LE.0 ) THEN RCOND = ONE RESID = ZERO RETURN END IF * * Exit with RESID = 1/EPS if ANORM = 0 or AINVNM = 0. * EPS = DLAMCH( 'Epsilon' ) ANORM = ZLANGE( '1', N, N, A, LDA, RWORK ) AINVNM = ZLANGE( '1', N, N, AINV, LDAINV, RWORK ) IF( ANORM.LE.ZERO .OR. AINVNM.LE.ZERO ) THEN RCOND = ZERO RESID = ONE / EPS RETURN END IF RCOND = ( ONE / ANORM ) / AINVNM * * Compute I - A * AINV * CALL ZGEMM( 'No transpose', 'No transpose', N, N, N, -CONE, AINV, \$ LDAINV, A, LDA, CZERO, WORK, LDWORK ) DO 10 I = 1, N WORK( I, I ) = CONE + WORK( I, I ) 10 CONTINUE * * Compute norm(I - AINV*A) / (N * norm(A) * norm(AINV) * EPS) * RESID = ZLANGE( '1', N, N, WORK, LDWORK, RWORK ) * RESID = ( ( RESID*RCOND ) / EPS ) / DBLE( N ) * RETURN * * End of ZGET03 * END