ssyconvf_rook()

subroutine ssyconvf_rook	(	character	uplo,
		character	way,
		integer	n,
		real, dimension( lda, * )	a,
		integer	lda,
		real, dimension( * )	e,
		integer, dimension( * )	ipiv,
		integer	info
	)

SSYCONVF_ROOK

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Purpose:

 If parameter WAY = 'C':
 SSYCONVF_ROOK converts the factorization output format used in
 SSYTRF_ROOK provided on entry in parameter A into the factorization
 output format used in SSYTRF_RK (or SSYTRF_BK) that is stored
 on exit in parameters A and E. IPIV format for SSYTRF_ROOK and
 SSYTRF_RK (or SSYTRF_BK) is the same and is not converted.

 If parameter WAY = 'R':
 SSYCONVF_ROOK performs the conversion in reverse direction, i.e.
 converts the factorization output format used in SSYTRF_RK
 (or SSYTRF_BK) provided on entry in parameters A and E into
 the factorization output format used in SSYTRF_ROOK that is stored
 on exit in parameter A. IPIV format for SSYTRF_ROOK and
 SSYTRF_RK (or SSYTRF_BK) is the same and is not converted.

Parameters

[in]	UPLO	UPLO is CHARACTER*1 Specifies whether the details of the factorization are stored as an upper or lower triangular matrix A. = 'U': Upper triangular = 'L': Lower triangular
[in]	WAY	WAY is CHARACTER*1 = 'C': Convert = 'R': Revert
[in]	N	N is INTEGER The order of the matrix A. N >= 0.
[in,out]	A	A is REAL array, dimension (LDA,N) 1) If WAY ='C': On entry, contains factorization details in format used in SSYTRF_ROOK: a) all elements of the symmetric block diagonal matrix D on the diagonal of A and on superdiagonal (or subdiagonal) of A, and b) If UPLO = 'U': multipliers used to obtain factor U in the superdiagonal part of A. If UPLO = 'L': multipliers used to obtain factor L in the superdiagonal part of A. On exit, contains factorization details in format used in SSYTRF_RK or SSYTRF_BK: a) ONLY diagonal elements of the symmetric block diagonal matrix D on the diagonal of A, i.e. D(k,k) = A(k,k); (superdiagonal (or subdiagonal) elements of D are stored on exit in array E), and b) If UPLO = 'U': factor U in the superdiagonal part of A. If UPLO = 'L': factor L in the subdiagonal part of A. 2) If WAY = 'R': On entry, contains factorization details in format used in SSYTRF_RK or SSYTRF_BK: a) ONLY diagonal elements of the symmetric block diagonal matrix D on the diagonal of A, i.e. D(k,k) = A(k,k); (superdiagonal (or subdiagonal) elements of D are stored on exit in array E), and b) If UPLO = 'U': factor U in the superdiagonal part of A. If UPLO = 'L': factor L in the subdiagonal part of A. On exit, contains factorization details in format used in SSYTRF_ROOK: a) all elements of the symmetric block diagonal matrix D on the diagonal of A and on superdiagonal (or subdiagonal) of A, and b) If UPLO = 'U': multipliers used to obtain factor U in the superdiagonal part of A. If UPLO = 'L': multipliers used to obtain factor L in the superdiagonal part of A.
[in]	LDA	LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).
[in,out]	E	E is REAL array, dimension (N) 1) If WAY ='C': On entry, just a workspace. On exit, contains the superdiagonal (or subdiagonal) elements of the symmetric block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks, where If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0; If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0. 2) If WAY = 'R': On entry, contains the superdiagonal (or subdiagonal) elements of the symmetric block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks, where If UPLO = 'U': E(i) = D(i-1,i),i=2:N, E(1) not referenced; If UPLO = 'L': E(i) = D(i+1,i),i=1:N-1, E(N) not referenced. On exit, is not changed
[in]	IPIV	IPIV is INTEGER array, dimension (N) On entry, details of the interchanges and the block structure of D as determined: 1) by SSYTRF_ROOK, if WAY ='C'; 2) by SSYTRF_RK (or SSYTRF_BK), if WAY ='R'. The IPIV format is the same for all these routines. On exit, is not changed.
[out]	INFO	INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Contributors:

  November 2017,  Igor Kozachenko,
                  Computer Science Division,
                  University of California, Berkeley

Definition at line 196 of file ssyconvf_rook.f.

*
*  -- LAPACK computational routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. 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           sswap, xerbla
*     .. Local Scalars ..
      LOGICAL            UPPER, CONVERT
      INTEGER            I, IP, IP2
*     ..
*     .. 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( 'SSYCONVF_ROOK', -info )
         RETURN
      END IF
*
*     Quick return if possible
*
      IF( n.EQ.0 )
     $   RETURN
*
      IF( upper ) THEN
*
*        Begin A is UPPER
*
         IF ( convert ) THEN
*
*           Convert A (A is upper)
*
*
*           Convert VALUE
*
*           Assign superdiagonal entries of D to array E and zero out
*           corresponding entries in input storage A
*
            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
               END IF
               i = i - 1
            END DO
*
*           Convert PERMUTATIONS
*
*           Apply permutations to submatrices of upper part of A
*           in factorization order where i decreases from N to 1
*
            i = n
            DO WHILE ( i.GE.1 )
               IF( ipiv( i ).GT.0 ) THEN
*
*                 1-by-1 pivot interchange
*
*                 Swap rows i and IPIV(i) in A(1:i,N-i:N)
*
                  ip = ipiv( i )
                  IF( i.LT.n ) THEN
                     IF( ip.NE.i ) THEN
                        CALL sswap( n-i, a( i, i+1 ), lda,
     $                              a( ip, i+1 ), lda )
                     END IF
                  END IF
*
               ELSE
*
*                 2-by-2 pivot interchange
*
*                 Swap rows i and IPIV(i) and i-1 and IPIV(i-1)
*                 in A(1:i,N-i:N)
*
                  ip = -ipiv( i )
                  ip2 = -ipiv( i-1 )
                  IF( i.LT.n ) THEN
                     IF( ip.NE.i ) THEN
                        CALL sswap( n-i, a( i, i+1 ), lda,
     $                              a( ip, i+1 ), lda )
                     END IF
                     IF( ip2.NE.(i-1) ) THEN
                        CALL sswap( n-i, a( i-1, i+1 ), lda,
     $                              a( ip2, i+1 ), lda )
                     END IF
                  END IF
                  i = i - 1
*
               END IF
               i = i - 1
            END DO
*
         ELSE
*
*           Revert A (A is upper)
*
*
*           Revert PERMUTATIONS
*
*           Apply permutations to submatrices of upper part of A
*           in reverse factorization order where i increases from 1 to N
*
            i = 1
            DO WHILE ( i.LE.n )
               IF( ipiv( i ).GT.0 ) THEN
*
*                 1-by-1 pivot interchange
*
*                 Swap rows i and IPIV(i) in A(1:i,N-i:N)
*
                  ip = ipiv( i )
                  IF( i.LT.n ) THEN
                     IF( ip.NE.i ) THEN
                        CALL sswap( n-i, a( ip, i+1 ), lda,
     $                              a( i, i+1 ), lda )
                     END IF
                  END IF
*
               ELSE
*
*                 2-by-2 pivot interchange
*
*                 Swap rows i-1 and IPIV(i-1) and i and IPIV(i)
*                 in A(1:i,N-i:N)
*
                  i = i + 1
                  ip = -ipiv( i )
                  ip2 = -ipiv( i-1 )
                  IF( i.LT.n ) THEN
                     IF( ip2.NE.(i-1) ) THEN
                        CALL sswap( n-i, a( ip2, i+1 ), lda,
     $                              a( i-1, i+1 ), lda )
                     END IF
                     IF( ip.NE.i ) THEN
                        CALL sswap( n-i, a( ip, i+1 ), lda,
     $                              a( i, i+1 ), lda )
                     END IF
                  END IF
*
               END IF
               i = i + 1
            END DO
*
*           Revert VALUE
*           Assign superdiagonal entries of D from array E to
*           superdiagonal entries of A.
*
            i = n
            DO WHILE ( i.GT.1 )
               IF( ipiv( i ).LT.0 ) THEN
                  a( i-1, i ) = e( i )
                  i = i - 1
               END IF
               i = i - 1
            END DO
*
*        End A is UPPER
*
         END IF
*
      ELSE
*
*        Begin A is LOWER
*
         IF ( convert ) THEN
*
*           Convert A (A is lower)
*
*
*           Convert VALUE
*           Assign subdiagonal entries of D to array E and zero out
*           corresponding entries in input storage A
*
            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
               END IF
               i = i + 1
            END DO
*
*           Convert PERMUTATIONS
*
*           Apply permutations to submatrices of lower part of A
*           in factorization order where i increases from 1 to N
*
            i = 1
            DO WHILE ( i.LE.n )
               IF( ipiv( i ).GT.0 ) THEN
*
*                 1-by-1 pivot interchange
*
*                 Swap rows i and IPIV(i) in A(i:N,1:i-1)
*
                  ip = ipiv( i )
                  IF ( i.GT.1 ) THEN
                     IF( ip.NE.i ) THEN
                        CALL sswap( i-1, a( i, 1 ), lda,
     $                              a( ip, 1 ), lda )
                     END IF
                  END IF
*
               ELSE
*
*                 2-by-2 pivot interchange
*
*                 Swap rows i and IPIV(i) and i+1 and IPIV(i+1)
*                 in A(i:N,1:i-1)
*
                  ip = -ipiv( i )
                  ip2 = -ipiv( i+1 )
                  IF ( i.GT.1 ) THEN
                     IF( ip.NE.i ) THEN
                        CALL sswap( i-1, a( i, 1 ), lda,
     $                              a( ip, 1 ), lda )
                     END IF
                     IF( ip2.NE.(i+1) ) THEN
                        CALL sswap( i-1, a( i+1, 1 ), lda,
     $                              a( ip2, 1 ), lda )
                     END IF
                  END IF
                  i = i + 1
*
               END IF
               i = i + 1
            END DO
*
         ELSE
*
*           Revert A (A is lower)
*
*
*           Revert PERMUTATIONS
*
*           Apply permutations to submatrices of lower part of A
*           in reverse factorization order where i decreases from N to 1
*
            i = n
            DO WHILE ( i.GE.1 )
               IF( ipiv( i ).GT.0 ) THEN
*
*                 1-by-1 pivot interchange
*
*                 Swap rows i and IPIV(i) in A(i:N,1:i-1)
*
                  ip = ipiv( i )
                  IF ( i.GT.1 ) THEN
                     IF( ip.NE.i ) THEN
                        CALL sswap( i-1, a( ip, 1 ), lda,
     $                              a( i, 1 ), lda )
                     END IF
                  END IF
*
               ELSE
*
*                 2-by-2 pivot interchange
*
*                 Swap rows i+1 and IPIV(i+1) and i and IPIV(i)
*                 in A(i:N,1:i-1)
*
                  i = i - 1
                  ip = -ipiv( i )
                  ip2 = -ipiv( i+1 )
                  IF ( i.GT.1 ) THEN
                     IF( ip2.NE.(i+1) ) THEN
                        CALL sswap( i-1, a( ip2, 1 ), lda,
     $                              a( i+1, 1 ), lda )
                     END IF
                     IF( ip.NE.i ) THEN
                        CALL sswap( i-1, a( ip, 1 ), lda,
     $                              a( i, 1 ), lda )
                     END IF
                  END IF
*
               END IF
               i = i - 1
            END DO
*
*           Revert VALUE
*           Assign subdiagonal entries of D from array E to
*           subdiagonal entries of A.
*
            i = 1
            DO WHILE ( i.LE.n-1 )
               IF( ipiv( i ).LT.0 ) THEN
                  a( i + 1, i ) = e( i )
                  i = i + 1
               END IF
               i = i + 1
            END DO
*
         END IF
*
*        End A is LOWER
*
      END IF
 
      RETURN
*
*     End of SSYCONVF_ROOK
*

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