LAPACK 3.3.0

sporfsx.f

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00001       SUBROUTINE SPORFSX( UPLO, EQUED, N, NRHS, A, LDA, AF, LDAF, S, B,
00002      $                    LDB, X, LDX, RCOND, BERR, N_ERR_BNDS,
00003      $                    ERR_BNDS_NORM, ERR_BNDS_COMP, NPARAMS, PARAMS,
00004      $                    WORK, IWORK, INFO )
00005 *
00006 *  -- LAPACK routine (version 3.2.2)                                  --
00007 *  -- Contributed by James Demmel, Deaglan Halligan, Yozo Hida and    --
00008 *  -- Jason Riedy of Univ. of California Berkeley.                    --
00009 *  -- June 2010                                                       --
00010 *
00011 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00012 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00013 *
00014       IMPLICIT NONE
00015 *     ..
00016 *     .. Scalar Arguments ..
00017       CHARACTER          UPLO, EQUED
00018       INTEGER            INFO, LDA, LDAF, LDB, LDX, N, NRHS, NPARAMS,
00019      $                   N_ERR_BNDS
00020       REAL               RCOND
00021 *     ..
00022 *     .. Array Arguments ..
00023       INTEGER            IWORK( * )
00024       REAL               A( LDA, * ), AF( LDAF, * ), B( LDB, * ),
00025      $                   X( LDX, * ), WORK( * )
00026       REAL               S( * ), PARAMS( * ), BERR( * ),
00027      $                   ERR_BNDS_NORM( NRHS, * ),
00028      $                   ERR_BNDS_COMP( NRHS, * )
00029 *     ..
00030 *
00031 *     Purpose
00032 *     =======
00033 *
00034 *     SPORFSX improves the computed solution to a system of linear
00035 *     equations when the coefficient matrix is symmetric positive
00036 *     definite, and provides error bounds and backward error estimates
00037 *     for the solution.  In addition to normwise error bound, the code
00038 *     provides maximum componentwise error bound if possible.  See
00039 *     comments for ERR_BNDS_NORM and ERR_BNDS_COMP for details of the
00040 *     error bounds.
00041 *
00042 *     The original system of linear equations may have been equilibrated
00043 *     before calling this routine, as described by arguments EQUED and S
00044 *     below. In this case, the solution and error bounds returned are
00045 *     for the original unequilibrated system.
00046 *
00047 *     Arguments
00048 *     =========
00049 *
00050 *     Some optional parameters are bundled in the PARAMS array.  These
00051 *     settings determine how refinement is performed, but often the
00052 *     defaults are acceptable.  If the defaults are acceptable, users
00053 *     can pass NPARAMS = 0 which prevents the source code from accessing
00054 *     the PARAMS argument.
00055 *
00056 *     UPLO    (input) CHARACTER*1
00057 *       = 'U':  Upper triangle of A is stored;
00058 *       = 'L':  Lower triangle of A is stored.
00059 *
00060 *     EQUED   (input) CHARACTER*1
00061 *     Specifies the form of equilibration that was done to A
00062 *     before calling this routine. This is needed to compute
00063 *     the solution and error bounds correctly.
00064 *       = 'N':  No equilibration
00065 *       = 'Y':  Both row and column equilibration, i.e., A has been
00066 *               replaced by diag(S) * A * diag(S).
00067 *               The right hand side B has been changed accordingly.
00068 *
00069 *     N       (input) INTEGER
00070 *     The order of the matrix A.  N >= 0.
00071 *
00072 *     NRHS    (input) INTEGER
00073 *     The number of right hand sides, i.e., the number of columns
00074 *     of the matrices B and X.  NRHS >= 0.
00075 *
00076 *     A       (input) REAL array, dimension (LDA,N)
00077 *     The symmetric matrix A.  If UPLO = 'U', the leading N-by-N
00078 *     upper triangular part of A contains the upper triangular part
00079 *     of the matrix A, and the strictly lower triangular part of A
00080 *     is not referenced.  If UPLO = 'L', the leading N-by-N lower
00081 *     triangular part of A contains the lower triangular part of
00082 *     the matrix A, and the strictly upper triangular part of A is
00083 *     not referenced.
00084 *
00085 *     LDA     (input) INTEGER
00086 *     The leading dimension of the array A.  LDA >= max(1,N).
00087 *
00088 *     AF      (input) REAL array, dimension (LDAF,N)
00089 *     The triangular factor U or L from the Cholesky factorization
00090 *     A = U**T*U or A = L*L**T, as computed by SPOTRF.
00091 *
00092 *     LDAF    (input) INTEGER
00093 *     The leading dimension of the array AF.  LDAF >= max(1,N).
00094 *
00095 *     S       (input or output) REAL array, dimension (N)
00096 *     The row scale factors for A.  If EQUED = 'Y', A is multiplied on
00097 *     the left and right by diag(S).  S is an input argument if FACT =
00098 *     'F'; otherwise, S is an output argument.  If FACT = 'F' and EQUED
00099 *     = 'Y', each element of S must be positive.  If S is output, each
00100 *     element of S is a power of the radix. If S is input, each element
00101 *     of S should be a power of the radix to ensure a reliable solution
00102 *     and error estimates. Scaling by powers of the radix does not cause
00103 *     rounding errors unless the result underflows or overflows.
00104 *     Rounding errors during scaling lead to refining with a matrix that
00105 *     is not equivalent to the input matrix, producing error estimates
00106 *     that may not be reliable.
00107 *
00108 *     B       (input) REAL array, dimension (LDB,NRHS)
00109 *     The right hand side matrix B.
00110 *
00111 *     LDB     (input) INTEGER
00112 *     The leading dimension of the array B.  LDB >= max(1,N).
00113 *
00114 *     X       (input/output) REAL array, dimension (LDX,NRHS)
00115 *     On entry, the solution matrix X, as computed by SGETRS.
00116 *     On exit, the improved solution matrix X.
00117 *
00118 *     LDX     (input) INTEGER
00119 *     The leading dimension of the array X.  LDX >= max(1,N).
00120 *
00121 *     RCOND   (output) REAL
00122 *     Reciprocal scaled condition number.  This is an estimate of the
00123 *     reciprocal Skeel condition number of the matrix A after
00124 *     equilibration (if done).  If this is less than the machine
00125 *     precision (in particular, if it is zero), the matrix is singular
00126 *     to working precision.  Note that the error may still be small even
00127 *     if this number is very small and the matrix appears ill-
00128 *     conditioned.
00129 *
00130 *     BERR    (output) REAL array, dimension (NRHS)
00131 *     Componentwise relative backward error.  This is the
00132 *     componentwise relative backward error of each solution vector X(j)
00133 *     (i.e., the smallest relative change in any element of A or B that
00134 *     makes X(j) an exact solution).
00135 *
00136 *     N_ERR_BNDS (input) INTEGER
00137 *     Number of error bounds to return for each right hand side
00138 *     and each type (normwise or componentwise).  See ERR_BNDS_NORM and
00139 *     ERR_BNDS_COMP below.
00140 *
00141 *     ERR_BNDS_NORM  (output) REAL array, dimension (NRHS, N_ERR_BNDS)
00142 *     For each right-hand side, this array contains information about
00143 *     various error bounds and condition numbers corresponding to the
00144 *     normwise relative error, which is defined as follows:
00145 *
00146 *     Normwise relative error in the ith solution vector:
00147 *             max_j (abs(XTRUE(j,i) - X(j,i)))
00148 *            ------------------------------
00149 *                  max_j abs(X(j,i))
00150 *
00151 *     The array is indexed by the type of error information as described
00152 *     below. There currently are up to three pieces of information
00153 *     returned.
00154 *
00155 *     The first index in ERR_BNDS_NORM(i,:) corresponds to the ith
00156 *     right-hand side.
00157 *
00158 *     The second index in ERR_BNDS_NORM(:,err) contains the following
00159 *     three fields:
00160 *     err = 1 "Trust/don't trust" boolean. Trust the answer if the
00161 *              reciprocal condition number is less than the threshold
00162 *              sqrt(n) * slamch('Epsilon').
00163 *
00164 *     err = 2 "Guaranteed" error bound: The estimated forward error,
00165 *              almost certainly within a factor of 10 of the true error
00166 *              so long as the next entry is greater than the threshold
00167 *              sqrt(n) * slamch('Epsilon'). This error bound should only
00168 *              be trusted if the previous boolean is true.
00169 *
00170 *     err = 3  Reciprocal condition number: Estimated normwise
00171 *              reciprocal condition number.  Compared with the threshold
00172 *              sqrt(n) * slamch('Epsilon') to determine if the error
00173 *              estimate is "guaranteed". These reciprocal condition
00174 *              numbers are 1 / (norm(Z^{-1},inf) * norm(Z,inf)) for some
00175 *              appropriately scaled matrix Z.
00176 *              Let Z = S*A, where S scales each row by a power of the
00177 *              radix so all absolute row sums of Z are approximately 1.
00178 *
00179 *     See Lapack Working Note 165 for further details and extra
00180 *     cautions.
00181 *
00182 *     ERR_BNDS_COMP  (output) REAL array, dimension (NRHS, N_ERR_BNDS)
00183 *     For each right-hand side, this array contains information about
00184 *     various error bounds and condition numbers corresponding to the
00185 *     componentwise relative error, which is defined as follows:
00186 *
00187 *     Componentwise relative error in the ith solution vector:
00188 *                    abs(XTRUE(j,i) - X(j,i))
00189 *             max_j ----------------------
00190 *                         abs(X(j,i))
00191 *
00192 *     The array is indexed by the right-hand side i (on which the
00193 *     componentwise relative error depends), and the type of error
00194 *     information as described below. There currently are up to three
00195 *     pieces of information returned for each right-hand side. If
00196 *     componentwise accuracy is not requested (PARAMS(3) = 0.0), then
00197 *     ERR_BNDS_COMP is not accessed.  If N_ERR_BNDS .LT. 3, then at most
00198 *     the first (:,N_ERR_BNDS) entries are returned.
00199 *
00200 *     The first index in ERR_BNDS_COMP(i,:) corresponds to the ith
00201 *     right-hand side.
00202 *
00203 *     The second index in ERR_BNDS_COMP(:,err) contains the following
00204 *     three fields:
00205 *     err = 1 "Trust/don't trust" boolean. Trust the answer if the
00206 *              reciprocal condition number is less than the threshold
00207 *              sqrt(n) * slamch('Epsilon').
00208 *
00209 *     err = 2 "Guaranteed" error bound: The estimated forward error,
00210 *              almost certainly within a factor of 10 of the true error
00211 *              so long as the next entry is greater than the threshold
00212 *              sqrt(n) * slamch('Epsilon'). This error bound should only
00213 *              be trusted if the previous boolean is true.
00214 *
00215 *     err = 3  Reciprocal condition number: Estimated componentwise
00216 *              reciprocal condition number.  Compared with the threshold
00217 *              sqrt(n) * slamch('Epsilon') to determine if the error
00218 *              estimate is "guaranteed". These reciprocal condition
00219 *              numbers are 1 / (norm(Z^{-1},inf) * norm(Z,inf)) for some
00220 *              appropriately scaled matrix Z.
00221 *              Let Z = S*(A*diag(x)), where x is the solution for the
00222 *              current right-hand side and S scales each row of
00223 *              A*diag(x) by a power of the radix so all absolute row
00224 *              sums of Z are approximately 1.
00225 *
00226 *     See Lapack Working Note 165 for further details and extra
00227 *     cautions.
00228 *
00229 *     NPARAMS (input) INTEGER
00230 *     Specifies the number of parameters set in PARAMS.  If .LE. 0, the
00231 *     PARAMS array is never referenced and default values are used.
00232 *
00233 *     PARAMS  (input / output) REAL array, dimension NPARAMS
00234 *     Specifies algorithm parameters.  If an entry is .LT. 0.0, then
00235 *     that entry will be filled with default value used for that
00236 *     parameter.  Only positions up to NPARAMS are accessed; defaults
00237 *     are used for higher-numbered parameters.
00238 *
00239 *       PARAMS(LA_LINRX_ITREF_I = 1) : Whether to perform iterative
00240 *            refinement or not.
00241 *         Default: 1.0
00242 *            = 0.0 : No refinement is performed, and no error bounds are
00243 *                    computed.
00244 *            = 1.0 : Use the double-precision refinement algorithm,
00245 *                    possibly with doubled-single computations if the
00246 *                    compilation environment does not support DOUBLE
00247 *                    PRECISION.
00248 *              (other values are reserved for future use)
00249 *
00250 *       PARAMS(LA_LINRX_ITHRESH_I = 2) : Maximum number of residual
00251 *            computations allowed for refinement.
00252 *         Default: 10
00253 *         Aggressive: Set to 100 to permit convergence using approximate
00254 *                     factorizations or factorizations other than LU. If
00255 *                     the factorization uses a technique other than
00256 *                     Gaussian elimination, the guarantees in
00257 *                     err_bnds_norm and err_bnds_comp may no longer be
00258 *                     trustworthy.
00259 *
00260 *       PARAMS(LA_LINRX_CWISE_I = 3) : Flag determining if the code
00261 *            will attempt to find a solution with small componentwise
00262 *            relative error in the double-precision algorithm.  Positive
00263 *            is true, 0.0 is false.
00264 *         Default: 1.0 (attempt componentwise convergence)
00265 *
00266 *     WORK    (workspace) REAL array, dimension (4*N)
00267 *
00268 *     IWORK   (workspace) INTEGER array, dimension (N)
00269 *
00270 *     INFO    (output) INTEGER
00271 *       = 0:  Successful exit. The solution to every right-hand side is
00272 *         guaranteed.
00273 *       < 0:  If INFO = -i, the i-th argument had an illegal value
00274 *       > 0 and <= N:  U(INFO,INFO) is exactly zero.  The factorization
00275 *         has been completed, but the factor U is exactly singular, so
00276 *         the solution and error bounds could not be computed. RCOND = 0
00277 *         is returned.
00278 *       = N+J: The solution corresponding to the Jth right-hand side is
00279 *         not guaranteed. The solutions corresponding to other right-
00280 *         hand sides K with K > J may not be guaranteed as well, but
00281 *         only the first such right-hand side is reported. If a small
00282 *         componentwise error is not requested (PARAMS(3) = 0.0) then
00283 *         the Jth right-hand side is the first with a normwise error
00284 *         bound that is not guaranteed (the smallest J such
00285 *         that ERR_BNDS_NORM(J,1) = 0.0). By default (PARAMS(3) = 1.0)
00286 *         the Jth right-hand side is the first with either a normwise or
00287 *         componentwise error bound that is not guaranteed (the smallest
00288 *         J such that either ERR_BNDS_NORM(J,1) = 0.0 or
00289 *         ERR_BNDS_COMP(J,1) = 0.0). See the definition of
00290 *         ERR_BNDS_NORM(:,1) and ERR_BNDS_COMP(:,1). To get information
00291 *         about all of the right-hand sides check ERR_BNDS_NORM or
00292 *         ERR_BNDS_COMP.
00293 *
00294 *     ==================================================================
00295 *
00296 *     .. Parameters ..
00297       REAL               ZERO, ONE
00298       PARAMETER          ( ZERO = 0.0E+0, ONE = 1.0E+0 )
00299       REAL               ITREF_DEFAULT, ITHRESH_DEFAULT,
00300      $                   COMPONENTWISE_DEFAULT
00301       REAL               RTHRESH_DEFAULT, DZTHRESH_DEFAULT
00302       PARAMETER          ( ITREF_DEFAULT = 1.0 )
00303       PARAMETER          ( ITHRESH_DEFAULT = 10.0 )
00304       PARAMETER          ( COMPONENTWISE_DEFAULT = 1.0 )
00305       PARAMETER          ( RTHRESH_DEFAULT = 0.5 )
00306       PARAMETER          ( DZTHRESH_DEFAULT = 0.25 )
00307       INTEGER            LA_LINRX_ITREF_I, LA_LINRX_ITHRESH_I,
00308      $                   LA_LINRX_CWISE_I
00309       PARAMETER          ( LA_LINRX_ITREF_I = 1,
00310      $                   LA_LINRX_ITHRESH_I = 2 )
00311       PARAMETER          ( LA_LINRX_CWISE_I = 3 )
00312       INTEGER            LA_LINRX_TRUST_I, LA_LINRX_ERR_I,
00313      $                   LA_LINRX_RCOND_I
00314       PARAMETER          ( LA_LINRX_TRUST_I = 1, LA_LINRX_ERR_I = 2 )
00315       PARAMETER          ( LA_LINRX_RCOND_I = 3 )
00316 *     ..
00317 *     .. Local Scalars ..
00318       CHARACTER(1)       NORM
00319       LOGICAL            RCEQU
00320       INTEGER            J, PREC_TYPE, REF_TYPE
00321       INTEGER            N_NORMS
00322       REAL               ANORM, RCOND_TMP
00323       REAL               ILLRCOND_THRESH, ERR_LBND, CWISE_WRONG
00324       LOGICAL            IGNORE_CWISE
00325       INTEGER            ITHRESH
00326       REAL               RTHRESH, UNSTABLE_THRESH
00327 *     ..
00328 *     .. External Subroutines ..
00329       EXTERNAL           XERBLA, SPOCON, SLA_PORFSX_EXTENDED
00330 *     ..
00331 *     .. Intrinsic Functions ..
00332       INTRINSIC          MAX, SQRT
00333 *     ..
00334 *     .. External Functions ..
00335       EXTERNAL           LSAME, BLAS_FPINFO_X, ILATRANS, ILAPREC
00336       EXTERNAL           SLAMCH, SLANSY, SLA_PORCOND
00337       REAL               SLAMCH, SLANSY, SLA_PORCOND
00338       LOGICAL            LSAME
00339       INTEGER            BLAS_FPINFO_X
00340       INTEGER            ILATRANS, ILAPREC
00341 *     ..
00342 *     .. Executable Statements ..
00343 *
00344 *     Check the input parameters.
00345 *
00346       INFO = 0
00347       REF_TYPE = INT( ITREF_DEFAULT )
00348       IF ( NPARAMS .GE. LA_LINRX_ITREF_I ) THEN
00349          IF ( PARAMS( LA_LINRX_ITREF_I ) .LT. 0.0 ) THEN
00350             PARAMS( LA_LINRX_ITREF_I ) = ITREF_DEFAULT
00351          ELSE
00352             REF_TYPE = PARAMS( LA_LINRX_ITREF_I )
00353          END IF
00354       END IF
00355 *
00356 *     Set default parameters.
00357 *
00358       ILLRCOND_THRESH = REAL( N ) * SLAMCH( 'Epsilon' )
00359       ITHRESH = INT( ITHRESH_DEFAULT )
00360       RTHRESH = RTHRESH_DEFAULT
00361       UNSTABLE_THRESH = DZTHRESH_DEFAULT
00362       IGNORE_CWISE = COMPONENTWISE_DEFAULT .EQ. 0.0
00363 *
00364       IF ( NPARAMS.GE.LA_LINRX_ITHRESH_I ) THEN
00365          IF ( PARAMS( LA_LINRX_ITHRESH_I ).LT.0.0 ) THEN
00366             PARAMS( LA_LINRX_ITHRESH_I ) = ITHRESH
00367          ELSE
00368             ITHRESH = INT( PARAMS( LA_LINRX_ITHRESH_I ) )
00369          END IF
00370       END IF
00371       IF ( NPARAMS.GE.LA_LINRX_CWISE_I ) THEN
00372          IF ( PARAMS( LA_LINRX_CWISE_I ).LT.0.0 ) THEN
00373             IF ( IGNORE_CWISE ) THEN
00374                PARAMS( LA_LINRX_CWISE_I ) = 0.0
00375             ELSE
00376                PARAMS( LA_LINRX_CWISE_I ) = 1.0
00377             END IF
00378          ELSE
00379             IGNORE_CWISE = PARAMS( LA_LINRX_CWISE_I ) .EQ. 0.0
00380          END IF
00381       END IF
00382       IF ( REF_TYPE .EQ. 0 .OR. N_ERR_BNDS .EQ. 0 ) THEN
00383          N_NORMS = 0
00384       ELSE IF ( IGNORE_CWISE ) THEN
00385          N_NORMS = 1
00386       ELSE
00387          N_NORMS = 2
00388       END IF
00389 *
00390       RCEQU = LSAME( EQUED, 'Y' )
00391 *
00392 *     Test input parameters.
00393 *
00394       IF (.NOT.LSAME(UPLO, 'U') .AND. .NOT.LSAME(UPLO, 'L')) THEN
00395         INFO = -1
00396       ELSE IF( .NOT.RCEQU .AND. .NOT.LSAME( EQUED, 'N' ) ) THEN
00397         INFO = -2
00398       ELSE IF( N.LT.0 ) THEN
00399         INFO = -3
00400       ELSE IF( NRHS.LT.0 ) THEN
00401         INFO = -4
00402       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
00403         INFO = -6
00404       ELSE IF( LDAF.LT.MAX( 1, N ) ) THEN
00405         INFO = -8
00406       ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
00407         INFO = -11
00408       ELSE IF( LDX.LT.MAX( 1, N ) ) THEN
00409         INFO = -13
00410       END IF
00411       IF( INFO.NE.0 ) THEN
00412         CALL XERBLA( 'SPORFSX', -INFO )
00413         RETURN
00414       END IF
00415 *
00416 *     Quick return if possible.
00417 *
00418       IF( N.EQ.0 .OR. NRHS.EQ.0 ) THEN
00419          RCOND = 1.0
00420          DO J = 1, NRHS
00421             BERR( J ) = 0.0
00422             IF ( N_ERR_BNDS .GE. 1 ) THEN
00423                ERR_BNDS_NORM( J, LA_LINRX_TRUST_I ) = 1.0
00424                ERR_BNDS_COMP( J, LA_LINRX_TRUST_I ) = 1.0
00425             END IF
00426             IF ( N_ERR_BNDS .GE. 2 ) THEN
00427                ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) = 0.0
00428                ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) = 0.0
00429             END IF
00430             IF ( N_ERR_BNDS .GE. 3 ) THEN
00431                ERR_BNDS_NORM( J, LA_LINRX_RCOND_I ) = 1.0
00432                ERR_BNDS_COMP( J, LA_LINRX_RCOND_I ) = 1.0
00433             END IF
00434          END DO
00435          RETURN
00436       END IF
00437 *
00438 *     Default to failure.
00439 *
00440       RCOND = 0.0
00441       DO J = 1, NRHS
00442          BERR( J ) = 1.0
00443          IF ( N_ERR_BNDS .GE. 1 ) THEN
00444             ERR_BNDS_NORM( J, LA_LINRX_TRUST_I ) = 1.0
00445             ERR_BNDS_COMP( J, LA_LINRX_TRUST_I ) = 1.0
00446          END IF
00447          IF ( N_ERR_BNDS .GE. 2 ) THEN
00448             ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) = 1.0
00449             ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) = 1.0
00450          END IF
00451          IF ( N_ERR_BNDS .GE. 3 ) THEN
00452             ERR_BNDS_NORM( J, LA_LINRX_RCOND_I ) = 0.0
00453             ERR_BNDS_COMP( J, LA_LINRX_RCOND_I ) = 0.0
00454          END IF
00455       END DO
00456 *
00457 *     Compute the norm of A and the reciprocal of the condition
00458 *     number of A.
00459 *
00460       NORM = 'I'
00461       ANORM = SLANSY( NORM, UPLO, N, A, LDA, WORK )
00462       CALL SPOCON( UPLO, N, AF, LDAF, ANORM, RCOND, WORK,
00463      $     IWORK, INFO )
00464 *
00465 *     Perform refinement on each right-hand side
00466 *
00467       IF ( REF_TYPE .NE. 0 ) THEN
00468 
00469          PREC_TYPE = ILAPREC( 'D' )
00470 
00471          CALL SLA_PORFSX_EXTENDED( PREC_TYPE, UPLO,  N,
00472      $        NRHS, A, LDA, AF, LDAF, RCEQU, S, B,
00473      $        LDB, X, LDX, BERR, N_NORMS, ERR_BNDS_NORM, ERR_BNDS_COMP,
00474      $        WORK( N+1 ), WORK( 1 ), WORK( 2*N+1 ), WORK( 1 ), RCOND,
00475      $        ITHRESH, RTHRESH, UNSTABLE_THRESH, IGNORE_CWISE,
00476      $        INFO )
00477       END IF
00478 
00479       ERR_LBND = MAX( 10.0, SQRT( REAL( N ) ) ) * SLAMCH( 'Epsilon' )
00480       IF ( N_ERR_BNDS .GE. 1 .AND. N_NORMS .GE. 1 ) THEN
00481 *
00482 *     Compute scaled normwise condition number cond(A*C).
00483 *
00484          IF ( RCEQU ) THEN
00485             RCOND_TMP = SLA_PORCOND( UPLO, N, A, LDA, AF, LDAF,
00486      $           -1, S, INFO, WORK, IWORK )
00487          ELSE
00488             RCOND_TMP = SLA_PORCOND( UPLO, N, A, LDA, AF, LDAF,
00489      $           0, S, INFO, WORK, IWORK )
00490          END IF
00491          DO J = 1, NRHS
00492 *
00493 *     Cap the error at 1.0.
00494 *
00495             IF ( N_ERR_BNDS .GE. LA_LINRX_ERR_I
00496      $           .AND. ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) .GT. 1.0 )
00497      $           ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) = 1.0
00498 *
00499 *     Threshold the error (see LAWN).
00500 *
00501             IF ( RCOND_TMP .LT. ILLRCOND_THRESH ) THEN
00502                ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) = 1.0
00503                ERR_BNDS_NORM( J, LA_LINRX_TRUST_I ) = 0.0
00504                IF ( INFO .LE. N ) INFO = N + J
00505             ELSE IF ( ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) .LT. ERR_LBND )
00506      $              THEN
00507                ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) = ERR_LBND
00508                ERR_BNDS_NORM( J, LA_LINRX_TRUST_I ) = 1.0
00509             END IF
00510 *
00511 *     Save the condition number.
00512 *
00513             IF (N_ERR_BNDS .GE. LA_LINRX_RCOND_I) THEN
00514                ERR_BNDS_NORM( J, LA_LINRX_RCOND_I ) = RCOND_TMP
00515             END IF
00516          END DO
00517       END IF
00518 
00519       IF ( N_ERR_BNDS .GE. 1 .AND. N_NORMS .GE. 2 ) THEN
00520 *
00521 *     Compute componentwise condition number cond(A*diag(Y(:,J))) for
00522 *     each right-hand side using the current solution as an estimate of
00523 *     the true solution.  If the componentwise error estimate is too
00524 *     large, then the solution is a lousy estimate of truth and the
00525 *     estimated RCOND may be too optimistic.  To avoid misleading users,
00526 *     the inverse condition number is set to 0.0 when the estimated
00527 *     cwise error is at least CWISE_WRONG.
00528 *
00529          CWISE_WRONG = SQRT( SLAMCH( 'Epsilon' ) )
00530          DO J = 1, NRHS
00531             IF (ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) .LT. CWISE_WRONG )
00532      $     THEN
00533                RCOND_TMP = SLA_PORCOND( UPLO, N, A, LDA, AF, LDAF, 1,
00534      $              X( 1, J ), INFO, WORK, IWORK )
00535             ELSE
00536                RCOND_TMP = 0.0
00537             END IF
00538 *
00539 *     Cap the error at 1.0.
00540 *
00541             IF ( N_ERR_BNDS .GE. LA_LINRX_ERR_I
00542      $           .AND. ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) .GT. 1.0 )
00543      $           ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) = 1.0
00544 *
00545 *     Threshold the error (see LAWN).
00546 *
00547             IF ( RCOND_TMP .LT. ILLRCOND_THRESH ) THEN
00548                ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) = 1.0
00549                ERR_BNDS_COMP( J, LA_LINRX_TRUST_I ) = 0.0
00550                IF ( PARAMS( LA_LINRX_CWISE_I ) .EQ. 1.0
00551      $              .AND. INFO.LT.N + J ) INFO = N + J
00552             ELSE IF ( ERR_BNDS_COMP( J, LA_LINRX_ERR_I )
00553      $              .LT. ERR_LBND ) THEN
00554                ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) = ERR_LBND
00555                ERR_BNDS_COMP( J, LA_LINRX_TRUST_I ) = 1.0
00556             END IF
00557 *
00558 *     Save the condition number.
00559 *
00560             IF ( N_ERR_BNDS .GE. LA_LINRX_RCOND_I ) THEN
00561                ERR_BNDS_COMP( J, LA_LINRX_RCOND_I ) = RCOND_TMP
00562             END IF
00563 
00564          END DO
00565       END IF
00566 *
00567       RETURN
00568 *
00569 *     End of SPORFSX
00570 *
00571       END
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