Mercurial > octave-nkf
view libcruft/odepack/ssolsy.f @ 16088:b29b10fbb744 stable release-3-6-4
Version 3.6.4 released.
* configure.ac (AC_INIT): Version is now 3.6.4.
(OCTAVE_RELEASE_DATE): Now 2013-02-21.
author | John W. Eaton <jwe@octave.org> |
---|---|
date | Thu, 21 Feb 2013 15:17:54 -0500 |
parents | 96ba591be50f |
children |
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SUBROUTINE SSOLSY (WM, IWM, X, TEM) C***BEGIN PROLOGUE SSOLSY C***SUBSIDIARY C***PURPOSE ODEPACK linear system solver. C***TYPE SINGLE PRECISION (SSOLSY-S, DSOLSY-D) C***AUTHOR Hindmarsh, Alan C., (LLNL) C***DESCRIPTION C C This routine manages the solution of the linear system arising from C a chord iteration. It is called if MITER .ne. 0. C If MITER is 1 or 2, it calls SGETRF to accomplish this. C If MITER = 3 it updates the coefficient h*EL0 in the diagonal C matrix, and then computes the solution. C If MITER is 4 or 5, it calls SGBTRS. C Communication with SSOLSY uses the following variables: C WM = real work space containing the inverse diagonal matrix if C MITER = 3 and the LU decomposition of the matrix otherwise. C Storage of matrix elements starts at WM(3). C WM also contains the following matrix-related data: C WM(1) = SQRT(UROUND) (not used here), C WM(2) = HL0, the previous value of h*EL0, used if MITER = 3. C IWM = integer work space containing pivot information, starting at C IWM(21), if MITER is 1, 2, 4, or 5. IWM also contains band C parameters ML = IWM(1) and MU = IWM(2) if MITER is 4 or 5. C X = the right-hand side vector on input, and the solution vector C on output, of length N. C TEM = vector of work space of length N, not used in this version. C IERSL = output flag (in COMMON). IERSL = 0 if no trouble occurred. C IERSL = 1 if a singular matrix arose with MITER = 3. C This routine also uses the COMMON variables EL0, H, MITER, and N. C C***SEE ALSO SLSODE C***ROUTINES CALLED SGBTRS, SGETRS C***COMMON BLOCKS SLS001 C***REVISION HISTORY (YYMMDD) C 791129 DATE WRITTEN C 890501 Modified prologue to SLATEC/LDOC format. (FNF) C 890503 Minor cosmetic changes. (FNF) C 930809 Renamed to allow single/double precision versions. (ACH) C 010412 Reduced size of Common block /SLS001/. (ACH) C 031105 Restored 'own' variables to Common block /SLS001/, to C enable interrupt/restart feature. (ACH) C***END PROLOGUE SSOLSY C**End INTEGER IWM REAL WM, X, TEM DIMENSION WM(*), IWM(*), X(*), TEM(*) INTEGER IOWND, IOWNS, 1 ICF, IERPJ, IERSL, JCUR, JSTART, KFLAG, L, 2 LYH, LEWT, LACOR, LSAVF, LWM, LIWM, METH, MITER, 3 MAXORD, MAXCOR, MSBP, MXNCF, N, NQ, NST, NFE, NJE, NQU REAL ROWNS, 1 CCMAX, EL0, H, HMIN, HMXI, HU, RC, TN, UROUND COMMON /SLS001/ ROWNS(209), 1 CCMAX, EL0, H, HMIN, HMXI, HU, RC, TN, UROUND, 2 IOWND(6), IOWNS(6), 3 ICF, IERPJ, IERSL, JCUR, JSTART, KFLAG, L, 4 LYH, LEWT, LACOR, LSAVF, LWM, LIWM, METH, MITER, 5 MAXORD, MAXCOR, MSBP, MXNCF, N, NQ, NST, NFE, NJE, NQU INTEGER I, MEBAND, ML, MU REAL DI, HL0, PHL0, R C C***FIRST EXECUTABLE STATEMENT SSOLSY IERSL = 0 GO TO (100, 100, 300, 400, 400), MITER 100 CALL SGETRS ( 'N', N, 1, WM(3), N, IWM(21), X, N, INLPCK) RETURN C 300 PHL0 = WM(2) HL0 = H*EL0 WM(2) = HL0 IF (HL0 .EQ. PHL0) GO TO 330 R = HL0/PHL0 DO 320 I = 1,N DI = 1.0E0 - R*(1.0E0 - 1.0E0/WM(I+2)) IF (ABS(DI) .EQ. 0.0E0) GO TO 390 320 WM(I+2) = 1.0E0/DI 330 DO 340 I = 1,N 340 X(I) = WM(I+2)*X(I) RETURN 390 IERSL = 1 RETURN C 400 ML = IWM(1) MU = IWM(2) MEBAND = 2*ML + MU + 1 CALL SGBTRS ( 'N', N, ML, MU, 1, WM(3), MEBAND, IWM(21), X, N, * INLPCK) RETURN C----------------------- END OF SUBROUTINE SSOLSY ---------------------- END