strt06.c
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00001 /* strt06.f -- translated by f2c (version 20061008).
00002    You must link the resulting object file with libf2c:
00003         on Microsoft Windows system, link with libf2c.lib;
00004         on Linux or Unix systems, link with .../path/to/libf2c.a -lm
00005         or, if you install libf2c.a in a standard place, with -lf2c -lm
00006         -- in that order, at the end of the command line, as in
00007                 cc *.o -lf2c -lm
00008         Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
00009 
00010                 http://www.netlib.org/f2c/libf2c.zip
00011 */
00012 
00013 #include "f2c.h"
00014 #include "blaswrap.h"
00015 
00016 /* Subroutine */ int strt06_(real *rcond, real *rcondc, char *uplo, char *
00017         diag, integer *n, real *a, integer *lda, real *work, real *rat)
00018 {
00019     /* System generated locals */
00020     integer a_dim1, a_offset;
00021     real r__1, r__2;
00022 
00023     /* Local variables */
00024     real eps, rmin, rmax, anorm;
00025     extern /* Subroutine */ int slabad_(real *, real *);
00026     extern doublereal slamch_(char *);
00027     real bignum;
00028     extern doublereal slantr_(char *, char *, char *, integer *, integer *, 
00029             real *, integer *, real *);
00030     real smlnum;
00031 
00032 
00033 /*  -- LAPACK test routine (version 3.1) -- */
00034 /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
00035 /*     November 2006 */
00036 
00037 /*     .. Scalar Arguments .. */
00038 /*     .. */
00039 /*     .. Array Arguments .. */
00040 /*     .. */
00041 
00042 /*  Purpose */
00043 /*  ======= */
00044 
00045 /*  STRT06 computes a test ratio comparing RCOND (the reciprocal */
00046 /*  condition number of a triangular matrix A) and RCONDC, the estimate */
00047 /*  computed by STRCON.  Information about the triangular matrix A is */
00048 /*  used if one estimate is zero and the other is non-zero to decide if */
00049 /*  underflow in the estimate is justified. */
00050 
00051 /*  Arguments */
00052 /*  ========= */
00053 
00054 /*  RCOND   (input) REAL */
00055 /*          The estimate of the reciprocal condition number obtained by */
00056 /*          forming the explicit inverse of the matrix A and computing */
00057 /*          RCOND = 1/( norm(A) * norm(inv(A)) ). */
00058 
00059 /*  RCONDC  (input) REAL */
00060 /*          The estimate of the reciprocal condition number computed by */
00061 /*          STRCON. */
00062 
00063 /*  UPLO    (input) CHARACTER */
00064 /*          Specifies whether the matrix A is upper or lower triangular. */
00065 /*          = 'U':  Upper triangular */
00066 /*          = 'L':  Lower triangular */
00067 
00068 /*  DIAG    (input) CHARACTER */
00069 /*          Specifies whether or not the matrix A is unit triangular. */
00070 /*          = 'N':  Non-unit triangular */
00071 /*          = 'U':  Unit triangular */
00072 
00073 /*  N       (input) INTEGER */
00074 /*          The order of the matrix A.  N >= 0. */
00075 
00076 /*  A       (input) REAL array, dimension (LDA,N) */
00077 /*          The triangular matrix A.  If UPLO = 'U', the leading n by n */
00078 /*          upper triangular part of the array A contains the upper */
00079 /*          triangular matrix, and the strictly lower triangular part of */
00080 /*          A is not referenced.  If UPLO = 'L', the leading n by n lower */
00081 /*          triangular part of the array A contains the lower triangular */
00082 /*          matrix, and the strictly upper triangular part of A is not */
00083 /*          referenced.  If DIAG = 'U', the diagonal elements of A are */
00084 /*          also not referenced and are assumed to be 1. */
00085 
00086 /*  LDA     (input) INTEGER */
00087 /*          The leading dimension of the array A.  LDA >= max(1,N). */
00088 
00089 /*  WORK    (workspace) REAL array, dimension (N) */
00090 
00091 /*  RAT     (output) REAL */
00092 /*          The test ratio.  If both RCOND and RCONDC are nonzero, */
00093 /*             RAT = MAX( RCOND, RCONDC )/MIN( RCOND, RCONDC ) - 1. */
00094 /*          If RAT = 0, the two estimates are exactly the same. */
00095 
00096 /*  ===================================================================== */
00097 
00098 /*     .. Parameters .. */
00099 /*     .. */
00100 /*     .. Local Scalars .. */
00101 /*     .. */
00102 /*     .. External Functions .. */
00103 /*     .. */
00104 /*     .. Intrinsic Functions .. */
00105 /*     .. */
00106 /*     .. External Subroutines .. */
00107 /*     .. */
00108 /*     .. Executable Statements .. */
00109 
00110     /* Parameter adjustments */
00111     a_dim1 = *lda;
00112     a_offset = 1 + a_dim1;
00113     a -= a_offset;
00114     --work;
00115 
00116     /* Function Body */
00117     eps = slamch_("Epsilon");
00118     rmax = dmax(*rcond,*rcondc);
00119     rmin = dmin(*rcond,*rcondc);
00120 
00121 /*     Do the easy cases first. */
00122 
00123     if (rmin < 0.f) {
00124 
00125 /*        Invalid value for RCOND or RCONDC, return 1/EPS. */
00126 
00127         *rat = 1.f / eps;
00128 
00129     } else if (rmin > 0.f) {
00130 
00131 /*        Both estimates are positive, return RMAX/RMIN - 1. */
00132 
00133         *rat = rmax / rmin - 1.f;
00134 
00135     } else if (rmax == 0.f) {
00136 
00137 /*        Both estimates zero. */
00138 
00139         *rat = 0.f;
00140 
00141     } else {
00142 
00143 /*        One estimate is zero, the other is non-zero.  If the matrix is */
00144 /*        ill-conditioned, return the nonzero estimate multiplied by */
00145 /*        1/EPS; if the matrix is badly scaled, return the nonzero */
00146 /*        estimate multiplied by BIGNUM/TMAX, where TMAX is the maximum */
00147 /*        element in absolute value in A. */
00148 
00149         smlnum = slamch_("Safe minimum");
00150         bignum = 1.f / smlnum;
00151         slabad_(&smlnum, &bignum);
00152         anorm = slantr_("M", uplo, diag, n, n, &a[a_offset], lda, &work[1]);
00153 
00154 /* Computing MIN */
00155         r__1 = bignum / dmax(1.f,anorm), r__2 = 1.f / eps;
00156         *rat = rmax * dmin(r__1,r__2);
00157     }
00158 
00159     return 0;
00160 
00161 /*     End of STRT06 */
00162 
00163 } /* strt06_ */


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autogenerated on Sat Jun 8 2019 18:56:15