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SUBROUTINE CPPT03( UPLO, N, A, AINV, 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 .. CHARACTER UPLO INTEGER LDWORK, N REAL RCOND, RESID * .. * .. Array Arguments .. REAL RWORK( * ) COMPLEX A( * ), AINV( * ), WORK( LDWORK, * ) * .. * * Purpose * ======= * * CPPT03 computes the residual for a Hermitian packed matrix times its * inverse: * norm( I - A*AINV ) / ( N * norm(A) * norm(AINV) * EPS ), * where EPS is the machine epsilon. * * Arguments * ========== * * UPLO (input) CHARACTER*1 * Specifies whether the upper or lower triangular part of the * Hermitian matrix A is stored: * = 'U': Upper triangular * = 'L': Lower triangular * * N (input) INTEGER * The number of rows and columns of the matrix A. N >= 0. * * A (input) COMPLEX array, dimension (N*(N+1)/2) * The original Hermitian matrix A, stored as a packed * triangular matrix. * * AINV (input) COMPLEX array, dimension (N*(N+1)/2) * The (Hermitian) inverse of the matrix A, stored as a packed * triangular matrix. * * WORK (workspace) COMPLEX array, dimension (LDWORK,N) * * LDWORK (input) INTEGER * The leading dimension of the array WORK. LDWORK >= max(1,N). * * RWORK (workspace) REAL array, dimension (N) * * RCOND (output) REAL * The reciprocal of the condition number of A, computed as * ( 1/norm(A) ) / norm(AINV). * * RESID (output) REAL * norm(I - A*AINV) / ( N * norm(A) * norm(AINV) * EPS ) * * ===================================================================== * * .. Parameters .. REAL ZERO, ONE PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0 ) COMPLEX CZERO, CONE PARAMETER ( CZERO = ( 0.0E+0, 0.0E+0 ), $ CONE = ( 1.0E+0, 0.0E+0 ) ) * .. * .. Local Scalars .. INTEGER I, J, JJ REAL AINVNM, ANORM, EPS * .. * .. External Functions .. LOGICAL LSAME REAL CLANGE, CLANHP, SLAMCH EXTERNAL LSAME, CLANGE, CLANHP, SLAMCH * .. * .. Intrinsic Functions .. INTRINSIC CONJG, REAL * .. * .. External Subroutines .. EXTERNAL CCOPY, CHPMV * .. * .. 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 = SLAMCH( 'Epsilon' ) ANORM = CLANHP( '1', UPLO, N, A, RWORK ) AINVNM = CLANHP( '1', UPLO, N, AINV, RWORK ) IF( ANORM.LE.ZERO .OR. AINVNM.LE.ZERO ) THEN RCOND = ZERO RESID = ONE / EPS RETURN END IF RCOND = ( ONE/ANORM ) / AINVNM * * UPLO = 'U': * Copy the leading N-1 x N-1 submatrix of AINV to WORK(1:N,2:N) and * expand it to a full matrix, then multiply by A one column at a * time, moving the result one column to the left. * IF( LSAME( UPLO, 'U' ) ) THEN * * Copy AINV * JJ = 1 DO 20 J = 1, N - 1 CALL CCOPY( J, AINV( JJ ), 1, WORK( 1, J+1 ), 1 ) DO 10 I = 1, J - 1 WORK( J, I+1 ) = CONJG( AINV( JJ+I-1 ) ) 10 CONTINUE JJ = JJ + J 20 CONTINUE JJ = ( ( N-1 )*N ) / 2 + 1 DO 30 I = 1, N - 1 WORK( N, I+1 ) = CONJG( AINV( JJ+I-1 ) ) 30 CONTINUE * * Multiply by A * DO 40 J = 1, N - 1 CALL CHPMV( 'Upper', N, -CONE, A, WORK( 1, J+1 ), 1, CZERO, $ WORK( 1, J ), 1 ) 40 CONTINUE CALL CHPMV( 'Upper', N, -CONE, A, AINV( JJ ), 1, CZERO, $ WORK( 1, N ), 1 ) * * UPLO = 'L': * Copy the trailing N-1 x N-1 submatrix of AINV to WORK(1:N,1:N-1) * and multiply by A, moving each column to the right. * ELSE * * Copy AINV * DO 50 I = 1, N - 1 WORK( 1, I ) = CONJG( AINV( I+1 ) ) 50 CONTINUE JJ = N + 1 DO 70 J = 2, N CALL CCOPY( N-J+1, AINV( JJ ), 1, WORK( J, J-1 ), 1 ) DO 60 I = 1, N - J WORK( J, J+I-1 ) = CONJG( AINV( JJ+I ) ) 60 CONTINUE JJ = JJ + N - J + 1 70 CONTINUE * * Multiply by A * DO 80 J = N, 2, -1 CALL CHPMV( 'Lower', N, -CONE, A, WORK( 1, J-1 ), 1, CZERO, $ WORK( 1, J ), 1 ) 80 CONTINUE CALL CHPMV( 'Lower', N, -CONE, A, AINV( 1 ), 1, CZERO, $ WORK( 1, 1 ), 1 ) * END IF * * Add the identity matrix to WORK . * DO 90 I = 1, N WORK( I, I ) = WORK( I, I ) + CONE 90 CONTINUE * * Compute norm(I - A*AINV) / (N * norm(A) * norm(AINV) * EPS) * RESID = CLANGE( '1', N, N, WORK, LDWORK, RWORK ) * RESID = ( ( RESID*RCOND )/EPS ) / REAL( N ) * RETURN * * End of CPPT03 * END |