REAL FUNCTION CLA_GBRCOND_C( TRANS, N, KL, KU, AB, LDAB, AFB, $ LDAFB, IPIV, C, CAPPLY, INFO, WORK, $ RWORK ) * * -- LAPACK routine (version 3.2) -- * -- Contributed by James Demmel, Deaglan Halligan, Yozo Hida and -- * -- Jason Riedy of Univ. of California Berkeley. -- * -- November 2008 -- * * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley and NAG Ltd. -- * IMPLICIT NONE * .. * .. Scalar Arguments .. CHARACTER TRANS LOGICAL CAPPLY INTEGER N, KL, KU, KD, LDAB, LDAFB, INFO * .. * .. Array Arguments .. INTEGER IPIV( * ) COMPLEX AB( LDAB, * ), AFB( LDAFB, * ), WORK( * ) REAL C( * ), RWORK( * ) * * CLA_GBRCOND_C Computes the infinity norm condition number of * op(A) * inv(diag(C)) where C is a REAL vector. * WORK is a COMPLEX workspace of size 2*N, and * RWORK is a REAL workspace of size 3*N. * .. * .. Local Scalars .. LOGICAL NOTRANS INTEGER KASE, I, J REAL AINVNM, ANORM, TMP COMPLEX ZDUM * .. * .. Local Arrays .. INTEGER ISAVE( 3 ) * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. * .. External Subroutines .. EXTERNAL CLACN2, CGBTRS, XERBLA * .. * .. Intrinsic Functions .. INTRINSIC ABS, MAX * .. * .. Statement Functions .. REAL CABS1 * .. * .. Statement Function Definitions .. CABS1( ZDUM ) = ABS( REAL( ZDUM ) ) + ABS( AIMAG( ZDUM ) ) * .. * .. Executable Statements .. CLA_GBRCOND_C = 0.0E+0 * INFO = 0 NOTRANS = LSAME( TRANS, 'N' ) IF ( .NOT. NOTRANS .AND. .NOT. LSAME( TRANS, 'T' ) .AND. .NOT. $ LSAME( TRANS, 'C' ) ) THEN ELSE IF( N.LT.0 ) THEN INFO = -2 END IF IF( INFO.NE.0 ) THEN CALL XERBLA( 'CLA_GBRCOND_C', -INFO ) RETURN END IF * * Compute norm of op(A)*op2(C). * ANORM = 0.0E+0 KD = KU + 1 IF ( NOTRANS ) THEN DO I = 1, N TMP = 0.0E+0 IF ( CAPPLY ) THEN DO J = 1, N IF ( I.GE.MAX( 1, J-KU ) $ .AND. I.LE.MIN( N, J+KL ) ) THEN TMP = TMP + CABS1(AB( KD+I-J, J ) ) / C( J ) END IF END DO ELSE DO J = 1, N IF ( I.GE.MAX( 1, J-KU ) $ .AND. I.LE.MIN( N, J+KL ) ) THEN TMP = TMP + CABS1( AB( KD+I-J, J ) ) END IF END DO END IF RWORK( 2*N+I ) = TMP ANORM = MAX( ANORM, TMP ) END DO ELSE DO I = 1, N TMP = 0.0E+0 IF ( CAPPLY ) THEN DO J = 1, N IF ( I.GE.MAX( 1, J-KU ) $ .AND. I.LE.MIN( N, J+KL ) ) THEN TMP = TMP + CABS1( AB( J, KD+I-J ) ) / C( J ) END IF END DO ELSE DO J = 1, N IF ( I.GE.MAX( 1, J-KU ) $ .AND. I.LE.MIN( N, J+KL ) ) THEN TMP = TMP + CABS1( AB( J, KD+I-J ) ) END IF END DO END IF RWORK( 2*N+I ) = TMP ANORM = MAX( ANORM, TMP ) END DO END IF * * Quick return if possible. * IF( N.EQ.0 ) THEN CLA_GBRCOND_C = 1.0E+0 RETURN ELSE IF( ANORM .EQ. 0.0E+0 ) THEN RETURN END IF * * Estimate the norm of inv(op(A)). * AINVNM = 0.0E+0 * KASE = 0 10 CONTINUE CALL CLACN2( N, WORK( N+1 ), WORK, AINVNM, KASE, ISAVE ) IF( KASE.NE.0 ) THEN IF( KASE.EQ.2 ) THEN * * Multiply by R. * DO I = 1, N WORK( I ) = WORK( I ) * RWORK( 2*N+I ) END DO * IF ( NOTRANS ) THEN CALL CGBTRS( 'No transpose', N, KL, KU, 1, AFB, LDAFB, $ IPIV, WORK, N, INFO ) ELSE CALL CGBTRS( 'Conjugate transpose', N, KL, KU, 1, AFB, $ LDAFB, IPIV, WORK, N, INFO ) ENDIF * * Multiply by inv(C). * IF ( CAPPLY ) THEN DO I = 1, N WORK( I ) = WORK( I ) * C( I ) END DO END IF ELSE * * Multiply by inv(C'). * IF ( CAPPLY ) THEN DO I = 1, N WORK( I ) = WORK( I ) * C( I ) END DO END IF * IF ( NOTRANS ) THEN CALL CGBTRS( 'Conjugate transpose', N, KL, KU, 1, AFB, $ LDAFB, IPIV, WORK, N, INFO ) ELSE CALL CGBTRS( 'No transpose', N, KL, KU, 1, AFB, LDAFB, $ IPIV, WORK, N, INFO ) END IF * * Multiply by R. * DO I = 1, N WORK( I ) = WORK( I ) * RWORK( 2*N+I ) END DO END IF GO TO 10 END IF * * Compute the estimate of the reciprocal condition number. * IF( AINVNM .NE. 0.0E+0 ) $ CLA_GBRCOND_C = 1.0E+0 / AINVNM * RETURN * END