229 lines
6.0 KiB
Fortran
229 lines
6.0 KiB
Fortran
*> \brief \b STPTRS
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
*> \htmlonly
|
|
*> Download STPTRS + dependencies
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/stptrs.f">
|
|
*> [TGZ]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/stptrs.f">
|
|
*> [ZIP]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/stptrs.f">
|
|
*> [TXT]</a>
|
|
*> \endhtmlonly
|
|
*
|
|
* Definition:
|
|
* ===========
|
|
*
|
|
* SUBROUTINE STPTRS( UPLO, TRANS, DIAG, N, NRHS, AP, B, LDB, INFO )
|
|
*
|
|
* .. Scalar Arguments ..
|
|
* CHARACTER DIAG, TRANS, UPLO
|
|
* INTEGER INFO, LDB, N, NRHS
|
|
* ..
|
|
* .. Array Arguments ..
|
|
* REAL AP( * ), B( LDB, * )
|
|
* ..
|
|
*
|
|
*
|
|
*> \par Purpose:
|
|
* =============
|
|
*>
|
|
*> \verbatim
|
|
*>
|
|
*> STPTRS solves a triangular system of the form
|
|
*>
|
|
*> A * X = B or A**T * X = B,
|
|
*>
|
|
*> where A is a triangular matrix of order N stored in packed format,
|
|
*> and B is an N-by-NRHS matrix. A check is made to verify that A is
|
|
*> nonsingular.
|
|
*> \endverbatim
|
|
*
|
|
* Arguments:
|
|
* ==========
|
|
*
|
|
*> \param[in] UPLO
|
|
*> \verbatim
|
|
*> UPLO is CHARACTER*1
|
|
*> = 'U': A is upper triangular;
|
|
*> = 'L': A is lower triangular.
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] TRANS
|
|
*> \verbatim
|
|
*> TRANS is CHARACTER*1
|
|
*> Specifies the form of the system of equations:
|
|
*> = 'N': A * X = B (No transpose)
|
|
*> = 'T': A**T * X = B (Transpose)
|
|
*> = 'C': A**H * X = B (Conjugate transpose = Transpose)
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] DIAG
|
|
*> \verbatim
|
|
*> DIAG is CHARACTER*1
|
|
*> = 'N': A is non-unit triangular;
|
|
*> = 'U': A is unit triangular.
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] N
|
|
*> \verbatim
|
|
*> N is INTEGER
|
|
*> The order of the matrix A. N >= 0.
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] NRHS
|
|
*> \verbatim
|
|
*> NRHS is INTEGER
|
|
*> The number of right hand sides, i.e., the number of columns
|
|
*> of the matrix B. NRHS >= 0.
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] AP
|
|
*> \verbatim
|
|
*> AP is REAL array, dimension (N*(N+1)/2)
|
|
*> The upper or lower triangular matrix A, packed columnwise in
|
|
*> a linear array. The j-th column of A is stored in the array
|
|
*> AP as follows:
|
|
*> if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
|
|
*> if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n.
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in,out] B
|
|
*> \verbatim
|
|
*> B is REAL array, dimension (LDB,NRHS)
|
|
*> On entry, the right hand side matrix B.
|
|
*> On exit, if INFO = 0, the solution matrix X.
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[in] LDB
|
|
*> \verbatim
|
|
*> LDB is INTEGER
|
|
*> The leading dimension of the array B. LDB >= max(1,N).
|
|
*> \endverbatim
|
|
*>
|
|
*> \param[out] INFO
|
|
*> \verbatim
|
|
*> INFO is INTEGER
|
|
*> = 0: successful exit
|
|
*> < 0: if INFO = -i, the i-th argument had an illegal value
|
|
*> > 0: if INFO = i, the i-th diagonal element of A is zero,
|
|
*> indicating that the matrix is singular and the
|
|
*> solutions X have not been computed.
|
|
*> \endverbatim
|
|
*
|
|
* Authors:
|
|
* ========
|
|
*
|
|
*> \author Univ. of Tennessee
|
|
*> \author Univ. of California Berkeley
|
|
*> \author Univ. of Colorado Denver
|
|
*> \author NAG Ltd.
|
|
*
|
|
*> \date December 2016
|
|
*
|
|
*> \ingroup realOTHERcomputational
|
|
*
|
|
* =====================================================================
|
|
SUBROUTINE STPTRS( UPLO, TRANS, DIAG, N, NRHS, AP, B, LDB, 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 DIAG, TRANS, UPLO
|
|
INTEGER INFO, LDB, N, NRHS
|
|
* ..
|
|
* .. Array Arguments ..
|
|
REAL AP( * ), B( LDB, * )
|
|
* ..
|
|
*
|
|
* =====================================================================
|
|
*
|
|
* .. Parameters ..
|
|
REAL ZERO
|
|
PARAMETER ( ZERO = 0.0E+0 )
|
|
* ..
|
|
* .. Local Scalars ..
|
|
LOGICAL NOUNIT, UPPER
|
|
INTEGER J, JC
|
|
* ..
|
|
* .. External Functions ..
|
|
LOGICAL LSAME
|
|
EXTERNAL LSAME
|
|
* ..
|
|
* .. External Subroutines ..
|
|
EXTERNAL STPSV, XERBLA
|
|
* ..
|
|
* .. Intrinsic Functions ..
|
|
INTRINSIC MAX
|
|
* ..
|
|
* .. Executable Statements ..
|
|
*
|
|
* Test the input parameters.
|
|
*
|
|
INFO = 0
|
|
UPPER = LSAME( UPLO, 'U' )
|
|
NOUNIT = LSAME( DIAG, 'N' )
|
|
IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
|
|
INFO = -1
|
|
ELSE IF( .NOT.LSAME( TRANS, 'N' ) .AND. .NOT.
|
|
$ LSAME( TRANS, 'T' ) .AND. .NOT.LSAME( TRANS, 'C' ) ) THEN
|
|
INFO = -2
|
|
ELSE IF( .NOT.NOUNIT .AND. .NOT.LSAME( DIAG, 'U' ) ) THEN
|
|
INFO = -3
|
|
ELSE IF( N.LT.0 ) THEN
|
|
INFO = -4
|
|
ELSE IF( NRHS.LT.0 ) THEN
|
|
INFO = -5
|
|
ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
|
|
INFO = -8
|
|
END IF
|
|
IF( INFO.NE.0 ) THEN
|
|
CALL XERBLA( 'STPTRS', -INFO )
|
|
RETURN
|
|
END IF
|
|
*
|
|
* Quick return if possible
|
|
*
|
|
IF( N.EQ.0 )
|
|
$ RETURN
|
|
*
|
|
* Check for singularity.
|
|
*
|
|
IF( NOUNIT ) THEN
|
|
IF( UPPER ) THEN
|
|
JC = 1
|
|
DO 10 INFO = 1, N
|
|
IF( AP( JC+INFO-1 ).EQ.ZERO )
|
|
$ RETURN
|
|
JC = JC + INFO
|
|
10 CONTINUE
|
|
ELSE
|
|
JC = 1
|
|
DO 20 INFO = 1, N
|
|
IF( AP( JC ).EQ.ZERO )
|
|
$ RETURN
|
|
JC = JC + N - INFO + 1
|
|
20 CONTINUE
|
|
END IF
|
|
END IF
|
|
INFO = 0
|
|
*
|
|
* Solve A * x = b or A**T * x = b.
|
|
*
|
|
DO 30 J = 1, NRHS
|
|
CALL STPSV( UPLO, TRANS, DIAG, N, AP, B( 1, J ), 1 )
|
|
30 CONTINUE
|
|
*
|
|
RETURN
|
|
*
|
|
* End of STPTRS
|
|
*
|
|
END
|