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/* dla_gbrpvgrw.f -- translated by f2c (version 20061008).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
#include "blaswrap.h"
doublereal dla_gbrpvgrw__(integer *n, integer *kl, integer *ku, integer *
ncols, doublereal *ab, integer *ldab, doublereal *afb, integer *ldafb)
{
/* System generated locals */
integer ab_dim1, ab_offset, afb_dim1, afb_offset, i__1, i__2, i__3, i__4;
doublereal ret_val, d__1, d__2;
/* Local variables */
integer i__, j, kd;
doublereal amax, umax, rpvgrw;
/* -- LAPACK routine (version 3.2.1) -- */
/* -- Contributed by James Demmel, Deaglan Halligan, Yozo Hida and -- */
/* -- Jason Riedy of Univ. of California Berkeley. -- */
/* -- April 2009 -- */
/* -- LAPACK is a software package provided by Univ. of Tennessee, -- */
/* -- Univ. of California Berkeley and NAG Ltd. -- */
/* .. */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DLA_GBRPVGRW computes the reciprocal pivot growth factor */
/* norm(A)/norm(U). The "max absolute element" norm is used. If this is */
/* much less than 1, the stability of the LU factorization of the */
/* (equilibrated) matrix A could be poor. This also means that the */
/* solution X, estimated condition numbers, and error bounds could be */
/* unreliable. */
/* Arguments */
/* ========= */
/* N (input) INTEGER */
/* The number of linear equations, i.e., the order of the */
/* matrix A. N >= 0. */
/* KL (input) INTEGER */
/* The number of subdiagonals within the band of A. KL >= 0. */
/* KU (input) INTEGER */
/* The number of superdiagonals within the band of A. KU >= 0. */
/* NCOLS (input) INTEGER */
/* The number of columns of the matrix A. NCOLS >= 0. */
/* AB (input) DOUBLE PRECISION array, dimension (LDAB,N) */
/* On entry, the matrix A in band storage, in rows 1 to KL+KU+1. */
/* The j-th column of A is stored in the j-th column of the */
/* array AB as follows: */
/* AB(KU+1+i-j,j) = A(i,j) for max(1,j-KU)<=i<=min(N,j+kl) */
/* LDAB (input) INTEGER */
/* The leading dimension of the array AB. LDAB >= KL+KU+1. */
/* AFB (input) DOUBLE PRECISION array, dimension (LDAFB,N) */
/* Details of the LU factorization of the band matrix A, as */
/* computed by DGBTRF. U is stored as an upper triangular */
/* band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, */
/* and the multipliers used during the factorization are stored */
/* in rows KL+KU+2 to 2*KL+KU+1. */
/* LDAFB (input) INTEGER */
/* The leading dimension of the array AFB. LDAFB >= 2*KL+KU+1. */
/* ===================================================================== */
/* .. Local Scalars .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Parameter adjustments */
ab_dim1 = *ldab;
ab_offset = 1 + ab_dim1;
ab -= ab_offset;
afb_dim1 = *ldafb;
afb_offset = 1 + afb_dim1;
afb -= afb_offset;
/* Function Body */
rpvgrw = 1.;
kd = *ku + 1;
i__1 = *ncols;
for (j = 1; j <= i__1; ++j) {
amax = 0.;
umax = 0.;
/* Computing MAX */
i__2 = j - *ku;
/* Computing MIN */
i__4 = j + *kl;
i__3 = min(i__4,*n);
for (i__ = max(i__2,1); i__ <= i__3; ++i__) {
/* Computing MAX */
d__2 = (d__1 = ab[kd + i__ - j + j * ab_dim1], abs(d__1));
amax = max(d__2,amax);
}
/* Computing MAX */
i__3 = j - *ku;
i__2 = j;
for (i__ = max(i__3,1); i__ <= i__2; ++i__) {
/* Computing MAX */
d__2 = (d__1 = afb[kd + i__ - j + j * afb_dim1], abs(d__1));
umax = max(d__2,umax);
}
if (umax != 0.) {
/* Computing MIN */
d__1 = amax / umax;
rpvgrw = min(d__1,rpvgrw);
}
}
ret_val = rpvgrw;
return ret_val;
} /* dla_gbrpvgrw__ */
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