*> \brief \b SSYCONV * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * *> \htmlonly *> Download SSYCONV + dependencies *> *> [TGZ] *> *> [ZIP] *> *> [TXT] *> \endhtmlonly * * Definition: * =========== * * SUBROUTINE SSYCONV( UPLO, WAY, N, A, LDA, IPIV, E, INFO ) * * .. Scalar Arguments .. * CHARACTER UPLO, WAY * INTEGER INFO, LDA, N * .. * .. Array Arguments .. * INTEGER IPIV( * ) * REAL A( LDA, * ), E( * ) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> SSYCONV convert A given by TRF into L and D and vice-versa. *> Get Non-diag elements of D (returned in workspace) and *> apply or reverse permutation done in TRF. *> \endverbatim * * Arguments: * ========== * *> \param[in] UPLO *> \verbatim *> UPLO is CHARACTER*1 *> Specifies whether the details of the factorization are stored *> as an upper or lower triangular matrix. *> = 'U': Upper triangular, form is A = U*D*U**T; *> = 'L': Lower triangular, form is A = L*D*L**T. *> \endverbatim *> *> \param[in] WAY *> \verbatim *> WAY is CHARACTER*1 *> = 'C': Convert *> = 'R': Revert *> \endverbatim *> *> \param[in] N *> \verbatim *> N is INTEGER *> The order of the matrix A. N >= 0. *> \endverbatim *> *> \param[in,out] A *> \verbatim *> A is REAL array, dimension (LDA,N) *> The block diagonal matrix D and the multipliers used to *> obtain the factor U or L as computed by SSYTRF. *> \endverbatim *> *> \param[in] LDA *> \verbatim *> LDA is INTEGER *> The leading dimension of the array A. LDA >= max(1,N). *> \endverbatim *> *> \param[in] IPIV *> \verbatim *> IPIV is INTEGER array, dimension (N) *> Details of the interchanges and the block structure of D *> as determined by SSYTRF. *> \endverbatim *> *> \param[out] E *> \verbatim *> E is REAL array, dimension (N) *> E stores the supdiagonal/subdiagonal of the symmetric 1-by-1 *> or 2-by-2 block diagonal matrix D in LDLT. *> \endverbatim *> *> \param[out] INFO *> \verbatim *> INFO is INTEGER *> = 0: successful exit *> < 0: if INFO = -i, the i-th argument had an illegal value *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \date December 2016 * *> \ingroup realSYcomputational * * ===================================================================== SUBROUTINE SSYCONV( UPLO, WAY, N, A, LDA, IPIV, E, INFO ) * * -- LAPACK computational routine (version 3.7.0) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * December 2016 * * .. Scalar Arguments .. CHARACTER UPLO, WAY INTEGER INFO, LDA, N * .. * .. Array Arguments .. INTEGER IPIV( * ) REAL A( LDA, * ), E( * ) * .. * * ===================================================================== * * .. Parameters .. REAL ZERO PARAMETER ( ZERO = 0.0E+0 ) * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * * .. External Subroutines .. EXTERNAL XERBLA * .. Local Scalars .. LOGICAL UPPER, CONVERT INTEGER I, IP, J REAL TEMP * .. * .. Executable Statements .. * INFO = 0 UPPER = LSAME( UPLO, 'U' ) CONVERT = LSAME( WAY, 'C' ) IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN INFO = -1 ELSE IF( .NOT.CONVERT .AND. .NOT.LSAME( WAY, 'R' ) ) THEN INFO = -2 ELSE IF( N.LT.0 ) THEN INFO = -3 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN INFO = -5 END IF IF( INFO.NE.0 ) THEN CALL XERBLA( 'SSYCONV', -INFO ) RETURN END IF * * Quick return if possible * IF( N.EQ.0 ) $ RETURN * IF( UPPER ) THEN * * A is UPPER * * Convert A (A is upper) * * Convert VALUE * IF ( CONVERT ) THEN I=N E(1)=ZERO DO WHILE ( I .GT. 1 ) IF( IPIV(I) .LT. 0 ) THEN E(I)=A(I-1,I) E(I-1)=ZERO A(I-1,I)=ZERO I=I-1 ELSE E(I)=ZERO ENDIF I=I-1 END DO * * Convert PERMUTATIONS * I=N DO WHILE ( I .GE. 1 ) IF( IPIV(I) .GT. 0) THEN IP=IPIV(I) IF( I .LT. N) THEN DO 12 J= I+1,N TEMP=A(IP,J) A(IP,J)=A(I,J) A(I,J)=TEMP 12 CONTINUE ENDIF ELSE IP=-IPIV(I) IF( I .LT. N) THEN DO 13 J= I+1,N TEMP=A(IP,J) A(IP,J)=A(I-1,J) A(I-1,J)=TEMP 13 CONTINUE ENDIF I=I-1 ENDIF I=I-1 END DO ELSE * * Revert A (A is upper) * * * Revert PERMUTATIONS * I=1 DO WHILE ( I .LE. N ) IF( IPIV(I) .GT. 0 ) THEN IP=IPIV(I) IF( I .LT. N) THEN DO J= I+1,N TEMP=A(IP,J) A(IP,J)=A(I,J) A(I,J)=TEMP END DO ENDIF ELSE IP=-IPIV(I) I=I+1 IF( I .LT. N) THEN DO J= I+1,N TEMP=A(IP,J) A(IP,J)=A(I-1,J) A(I-1,J)=TEMP END DO ENDIF ENDIF I=I+1 END DO * * Revert VALUE * I=N DO WHILE ( I .GT. 1 ) IF( IPIV(I) .LT. 0 ) THEN A(I-1,I)=E(I) I=I-1 ENDIF I=I-1 END DO END IF ELSE * * A is LOWER * IF ( CONVERT ) THEN * * Convert A (A is lower) * * * Convert VALUE * I=1 E(N)=ZERO DO WHILE ( I .LE. N ) IF( I.LT.N .AND. IPIV(I) .LT. 0 ) THEN E(I)=A(I+1,I) E(I+1)=ZERO A(I+1,I)=ZERO I=I+1 ELSE E(I)=ZERO ENDIF I=I+1 END DO * * Convert PERMUTATIONS * I=1 DO WHILE ( I .LE. N ) IF( IPIV(I) .GT. 0 ) THEN IP=IPIV(I) IF (I .GT. 1) THEN DO 22 J= 1,I-1 TEMP=A(IP,J) A(IP,J)=A(I,J) A(I,J)=TEMP 22 CONTINUE ENDIF ELSE IP=-IPIV(I) IF (I .GT. 1) THEN DO 23 J= 1,I-1 TEMP=A(IP,J) A(IP,J)=A(I+1,J) A(I+1,J)=TEMP 23 CONTINUE ENDIF I=I+1 ENDIF I=I+1 END DO ELSE * * Revert A (A is lower) * * * Revert PERMUTATIONS * I=N DO WHILE ( I .GE. 1 ) IF( IPIV(I) .GT. 0 ) THEN IP=IPIV(I) IF (I .GT. 1) THEN DO J= 1,I-1 TEMP=A(I,J) A(I,J)=A(IP,J) A(IP,J)=TEMP END DO ENDIF ELSE IP=-IPIV(I) I=I-1 IF (I .GT. 1) THEN DO J= 1,I-1 TEMP=A(I+1,J) A(I+1,J)=A(IP,J) A(IP,J)=TEMP END DO ENDIF ENDIF I=I-1 END DO * * Revert VALUE * I=1 DO WHILE ( I .LE. N-1 ) IF( IPIV(I) .LT. 0 ) THEN A(I+1,I)=E(I) I=I+1 ENDIF I=I+1 END DO END IF END IF RETURN * * End of SSYCONV * END