Annotation of rpl/lapack/lapack/zpttrs.f, revision 1.9
1.9 ! bertrand 1: *> \brief \b ZPTTRS
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: *> \htmlonly
! 9: *> Download ZPTTRS + dependencies
! 10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zpttrs.f">
! 11: *> [TGZ]</a>
! 12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zpttrs.f">
! 13: *> [ZIP]</a>
! 14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zpttrs.f">
! 15: *> [TXT]</a>
! 16: *> \endhtmlonly
! 17: *
! 18: * Definition:
! 19: * ===========
! 20: *
! 21: * SUBROUTINE ZPTTRS( UPLO, N, NRHS, D, E, B, LDB, INFO )
! 22: *
! 23: * .. Scalar Arguments ..
! 24: * CHARACTER UPLO
! 25: * INTEGER INFO, LDB, N, NRHS
! 26: * ..
! 27: * .. Array Arguments ..
! 28: * DOUBLE PRECISION D( * )
! 29: * COMPLEX*16 B( LDB, * ), E( * )
! 30: * ..
! 31: *
! 32: *
! 33: *> \par Purpose:
! 34: * =============
! 35: *>
! 36: *> \verbatim
! 37: *>
! 38: *> ZPTTRS solves a tridiagonal system of the form
! 39: *> A * X = B
! 40: *> using the factorization A = U**H *D* U or A = L*D*L**H computed by ZPTTRF.
! 41: *> D is a diagonal matrix specified in the vector D, U (or L) is a unit
! 42: *> bidiagonal matrix whose superdiagonal (subdiagonal) is specified in
! 43: *> the vector E, and X and B are N by NRHS matrices.
! 44: *> \endverbatim
! 45: *
! 46: * Arguments:
! 47: * ==========
! 48: *
! 49: *> \param[in] UPLO
! 50: *> \verbatim
! 51: *> UPLO is CHARACTER*1
! 52: *> Specifies the form of the factorization and whether the
! 53: *> vector E is the superdiagonal of the upper bidiagonal factor
! 54: *> U or the subdiagonal of the lower bidiagonal factor L.
! 55: *> = 'U': A = U**H *D*U, E is the superdiagonal of U
! 56: *> = 'L': A = L*D*L**H, E is the subdiagonal of L
! 57: *> \endverbatim
! 58: *>
! 59: *> \param[in] N
! 60: *> \verbatim
! 61: *> N is INTEGER
! 62: *> The order of the tridiagonal matrix A. N >= 0.
! 63: *> \endverbatim
! 64: *>
! 65: *> \param[in] NRHS
! 66: *> \verbatim
! 67: *> NRHS is INTEGER
! 68: *> The number of right hand sides, i.e., the number of columns
! 69: *> of the matrix B. NRHS >= 0.
! 70: *> \endverbatim
! 71: *>
! 72: *> \param[in] D
! 73: *> \verbatim
! 74: *> D is DOUBLE PRECISION array, dimension (N)
! 75: *> The n diagonal elements of the diagonal matrix D from the
! 76: *> factorization A = U**H *D*U or A = L*D*L**H.
! 77: *> \endverbatim
! 78: *>
! 79: *> \param[in] E
! 80: *> \verbatim
! 81: *> E is COMPLEX*16 array, dimension (N-1)
! 82: *> If UPLO = 'U', the (n-1) superdiagonal elements of the unit
! 83: *> bidiagonal factor U from the factorization A = U**H*D*U.
! 84: *> If UPLO = 'L', the (n-1) subdiagonal elements of the unit
! 85: *> bidiagonal factor L from the factorization A = L*D*L**H.
! 86: *> \endverbatim
! 87: *>
! 88: *> \param[in,out] B
! 89: *> \verbatim
! 90: *> B is DOUBLE PRECISION array, dimension (LDB,NRHS)
! 91: *> On entry, the right hand side vectors B for the system of
! 92: *> linear equations.
! 93: *> On exit, the solution vectors, X.
! 94: *> \endverbatim
! 95: *>
! 96: *> \param[in] LDB
! 97: *> \verbatim
! 98: *> LDB is INTEGER
! 99: *> The leading dimension of the array B. LDB >= max(1,N).
! 100: *> \endverbatim
! 101: *>
! 102: *> \param[out] INFO
! 103: *> \verbatim
! 104: *> INFO is INTEGER
! 105: *> = 0: successful exit
! 106: *> < 0: if INFO = -k, the k-th argument had an illegal value
! 107: *> \endverbatim
! 108: *
! 109: * Authors:
! 110: * ========
! 111: *
! 112: *> \author Univ. of Tennessee
! 113: *> \author Univ. of California Berkeley
! 114: *> \author Univ. of Colorado Denver
! 115: *> \author NAG Ltd.
! 116: *
! 117: *> \date November 2011
! 118: *
! 119: *> \ingroup complex16OTHERcomputational
! 120: *
! 121: * =====================================================================
1.1 bertrand 122: SUBROUTINE ZPTTRS( UPLO, N, NRHS, D, E, B, LDB, INFO )
123: *
1.9 ! bertrand 124: * -- LAPACK computational routine (version 3.4.0) --
1.1 bertrand 125: * -- LAPACK is a software package provided by Univ. of Tennessee, --
126: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.9 ! bertrand 127: * November 2011
1.1 bertrand 128: *
129: * .. Scalar Arguments ..
130: CHARACTER UPLO
131: INTEGER INFO, LDB, N, NRHS
132: * ..
133: * .. Array Arguments ..
134: DOUBLE PRECISION D( * )
135: COMPLEX*16 B( LDB, * ), E( * )
136: * ..
137: *
138: * =====================================================================
139: *
140: * .. Local Scalars ..
141: LOGICAL UPPER
142: INTEGER IUPLO, J, JB, NB
143: * ..
144: * .. External Functions ..
145: INTEGER ILAENV
146: EXTERNAL ILAENV
147: * ..
148: * .. External Subroutines ..
149: EXTERNAL XERBLA, ZPTTS2
150: * ..
151: * .. Intrinsic Functions ..
152: INTRINSIC MAX, MIN
153: * ..
154: * .. Executable Statements ..
155: *
156: * Test the input arguments.
157: *
158: INFO = 0
159: UPPER = ( UPLO.EQ.'U' .OR. UPLO.EQ.'u' )
160: IF( .NOT.UPPER .AND. .NOT.( UPLO.EQ.'L' .OR. UPLO.EQ.'l' ) ) THEN
161: INFO = -1
162: ELSE IF( N.LT.0 ) THEN
163: INFO = -2
164: ELSE IF( NRHS.LT.0 ) THEN
165: INFO = -3
166: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
167: INFO = -7
168: END IF
169: IF( INFO.NE.0 ) THEN
170: CALL XERBLA( 'ZPTTRS', -INFO )
171: RETURN
172: END IF
173: *
174: * Quick return if possible
175: *
176: IF( N.EQ.0 .OR. NRHS.EQ.0 )
177: $ RETURN
178: *
179: * Determine the number of right-hand sides to solve at a time.
180: *
181: IF( NRHS.EQ.1 ) THEN
182: NB = 1
183: ELSE
184: NB = MAX( 1, ILAENV( 1, 'ZPTTRS', UPLO, N, NRHS, -1, -1 ) )
185: END IF
186: *
187: * Decode UPLO
188: *
189: IF( UPPER ) THEN
190: IUPLO = 1
191: ELSE
192: IUPLO = 0
193: END IF
194: *
195: IF( NB.GE.NRHS ) THEN
196: CALL ZPTTS2( IUPLO, N, NRHS, D, E, B, LDB )
197: ELSE
198: DO 10 J = 1, NRHS, NB
199: JB = MIN( NRHS-J+1, NB )
200: CALL ZPTTS2( IUPLO, N, JB, D, E, B( 1, J ), LDB )
201: 10 CONTINUE
202: END IF
203: *
204: RETURN
205: *
206: * End of ZPTTRS
207: *
208: END
CVSweb interface <joel.bertrand@systella.fr>
![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to zpttrs.f CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [local] / rpl / lapack / lapack