cla_lin_berr.c
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00001 /* cla_lin_berr.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 cla_lin_berr__(integer *n, integer *nz, integer *nrhs, 
00017         complex *res, real *ayb, real *berr)
00018 {
00019     /* System generated locals */
00020     integer ayb_dim1, ayb_offset, res_dim1, res_offset, i__1, i__2, i__3, 
00021             i__4;
00022     real r__1, r__2, r__3;
00023     complex q__1, q__2, q__3;
00024 
00025     /* Builtin functions */
00026     double r_imag(complex *);
00027 
00028     /* Local variables */
00029     integer i__, j;
00030     real tmp, safe1;
00031     extern doublereal slamch_(char *);
00032 
00033 
00034 /*     -- LAPACK routine (version 3.2.1)                                 -- */
00035 /*     -- Contributed by James Demmel, Deaglan Halligan, Yozo Hida and -- */
00036 /*     -- Jason Riedy of Univ. of California Berkeley.                 -- */
00037 /*     -- April 2009                                                   -- */
00038 
00039 /*     -- LAPACK is a software package provided by Univ. of Tennessee, -- */
00040 /*     -- Univ. of California Berkeley and NAG Ltd.                    -- */
00041 
00042 /*     .. */
00043 /*     .. Scalar Arguments .. */
00044 /*     .. */
00045 /*     .. Array Arguments .. */
00046 /*     .. */
00047 
00048 /*  Purpose */
00049 /*  ======= */
00050 
00051 /*     CLA_LIN_BERR computes componentwise relative backward error from */
00052 /*     the formula */
00053 /*         max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) ) */
00054 /*     where abs(Z) is the componentwise absolute value of the matrix */
00055 /*     or vector Z. */
00056 
00057 /*     N       (input) INTEGER */
00058 /*     The number of linear equations, i.e., the order of the */
00059 /*     matrix A.  N >= 0. */
00060 
00061 /*     NZ      (input) INTEGER */
00062 /*     We add (NZ+1)*SLAMCH( 'Safe minimum' ) to R(i) in the numerator to */
00063 /*     guard against spuriously zero residuals. Default value is N. */
00064 
00065 /*     NRHS    (input) INTEGER */
00066 /*     The number of right hand sides, i.e., the number of columns */
00067 /*     of the matrices AYB, RES, and BERR.  NRHS >= 0. */
00068 
00069 /*     RES    (input) DOUBLE PRECISION array, dimension (N,NRHS) */
00070 /*     The residual matrix, i.e., the matrix R in the relative backward */
00071 /*     error formula above. */
00072 
00073 /*     AYB    (input) DOUBLE PRECISION array, dimension (N, NRHS) */
00074 /*     The denominator in the relative backward error formula above, i.e., */
00075 /*     the matrix abs(op(A_s))*abs(Y) + abs(B_s). The matrices A, Y, and B */
00076 /*     are from iterative refinement (see cla_gerfsx_extended.f). */
00077 
00078 /*     RES    (output) COMPLEX array, dimension (NRHS) */
00079 /*     The componentwise relative backward error from the formula above. */
00080 
00081 /*  ===================================================================== */
00082 
00083 /*     .. Local Scalars .. */
00084 /*     .. */
00085 /*     .. Intrinsic Functions .. */
00086 /*     .. */
00087 /*     .. External Functions .. */
00088 /*     .. */
00089 /*     .. Statement Functions .. */
00090 /*     .. */
00091 /*     .. Statement Function Definitions .. */
00092 /*     .. */
00093 /*     .. Executable Statements .. */
00094 
00095 /*     Adding SAFE1 to the numerator guards against spuriously zero */
00096 /*     residuals.  A similar safeguard is in the CLA_yyAMV routine used */
00097 /*     to compute AYB. */
00098 
00099     /* Parameter adjustments */
00100     --berr;
00101     ayb_dim1 = *n;
00102     ayb_offset = 1 + ayb_dim1;
00103     ayb -= ayb_offset;
00104     res_dim1 = *n;
00105     res_offset = 1 + res_dim1;
00106     res -= res_offset;
00107 
00108     /* Function Body */
00109     safe1 = slamch_("Safe minimum");
00110     safe1 = (*nz + 1) * safe1;
00111     i__1 = *nrhs;
00112     for (j = 1; j <= i__1; ++j) {
00113         berr[j] = 0.f;
00114         i__2 = *n;
00115         for (i__ = 1; i__ <= i__2; ++i__) {
00116             if (ayb[i__ + j * ayb_dim1] != 0.f) {
00117                 i__3 = i__ + j * res_dim1;
00118                 r__3 = (r__1 = res[i__3].r, dabs(r__1)) + (r__2 = r_imag(&res[
00119                         i__ + j * res_dim1]), dabs(r__2));
00120                 q__3.r = r__3, q__3.i = 0.f;
00121                 q__2.r = safe1 + q__3.r, q__2.i = q__3.i;
00122                 i__4 = i__ + j * ayb_dim1;
00123                 q__1.r = q__2.r / ayb[i__4], q__1.i = q__2.i / ayb[i__4];
00124                 tmp = q__1.r;
00125 /* Computing MAX */
00126                 r__1 = berr[j];
00127                 berr[j] = dmax(r__1,tmp);
00128             }
00129 
00130 /*     If AYB is exactly 0.0 (and if computed by CLA_yyAMV), then we know */
00131 /*     the true residual also must be exactly 0.0. */
00132 
00133         }
00134     }
00135     return 0;
00136 } /* cla_lin_berr__ */


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autogenerated on Sat Jun 8 2019 18:55:29