OpenBLAS/lapack-netlib/SRC/sgtsvx.c

#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <complex.h>
#ifdef complex
#undef complex
#endif
#ifdef I
#undef I
#endif

#if defined(_WIN64)
typedef long long BLASLONG;
typedef unsigned long long BLASULONG;
#else
typedef long BLASLONG;
typedef unsigned long BLASULONG;
#endif

#ifdef LAPACK_ILP64
typedef BLASLONG blasint;
#if defined(_WIN64)
#define blasabs(x) llabs(x)
#else
#define blasabs(x) labs(x)
#endif
#else
typedef int blasint;
#define blasabs(x) abs(x)
#endif

typedef blasint integer;

typedef unsigned int uinteger;
typedef char *address;
typedef short int shortint;
typedef float real;
typedef double doublereal;
typedef struct { real r, i; } complex;
typedef struct { doublereal r, i; } doublecomplex;
#ifdef _MSC_VER
static inline _Fcomplex Cf(complex *z) {_Fcomplex zz={z->r , z->i}; return zz;}
static inline _Dcomplex Cd(doublecomplex *z) {_Dcomplex zz={z->r , z->i};return zz;}
static inline _Fcomplex * _pCf(complex *z) {return (_Fcomplex*)z;}
static inline _Dcomplex * _pCd(doublecomplex *z) {return (_Dcomplex*)z;}
#else
static inline _Complex float Cf(complex *z) {return z->r + z->i*_Complex_I;}
static inline _Complex double Cd(doublecomplex *z) {return z->r + z->i*_Complex_I;}
static inline _Complex float * _pCf(complex *z) {return (_Complex float*)z;}
static inline _Complex double * _pCd(doublecomplex *z) {return (_Complex double*)z;}
#endif
#define pCf(z) (*_pCf(z))
#define pCd(z) (*_pCd(z))
typedef blasint logical;

typedef char logical1;
typedef char integer1;

#define TRUE_ (1)
#define FALSE_ (0)

/* Extern is for use with -E */
#ifndef Extern
#define Extern extern
#endif

/* I/O stuff */

typedef int flag;
typedef int ftnlen;
typedef int ftnint;

/*external read, write*/
typedef struct
{	flag cierr;
	ftnint ciunit;
	flag ciend;
	char *cifmt;
	ftnint cirec;
} cilist;

/*internal read, write*/
typedef struct
{	flag icierr;
	char *iciunit;
	flag iciend;
	char *icifmt;
	ftnint icirlen;
	ftnint icirnum;
} icilist;

/*open*/
typedef struct
{	flag oerr;
	ftnint ounit;
	char *ofnm;
	ftnlen ofnmlen;
	char *osta;
	char *oacc;
	char *ofm;
	ftnint orl;
	char *oblnk;
} olist;

/*close*/
typedef struct
{	flag cerr;
	ftnint cunit;
	char *csta;
} cllist;

/*rewind, backspace, endfile*/
typedef struct
{	flag aerr;
	ftnint aunit;
} alist;

/* inquire */
typedef struct
{	flag inerr;
	ftnint inunit;
	char *infile;
	ftnlen infilen;
	ftnint	*inex;	/*parameters in standard's order*/
	ftnint	*inopen;
	ftnint	*innum;
	ftnint	*innamed;
	char	*inname;
	ftnlen	innamlen;
	char	*inacc;
	ftnlen	inacclen;
	char	*inseq;
	ftnlen	inseqlen;
	char 	*indir;
	ftnlen	indirlen;
	char	*infmt;
	ftnlen	infmtlen;
	char	*inform;
	ftnint	informlen;
	char	*inunf;
	ftnlen	inunflen;
	ftnint	*inrecl;
	ftnint	*innrec;
	char	*inblank;
	ftnlen	inblanklen;
} inlist;

#define VOID void

union Multitype {	/* for multiple entry points */
	integer1 g;
	shortint h;
	integer i;
	/* longint j; */
	real r;
	doublereal d;
	complex c;
	doublecomplex z;
	};

typedef union Multitype Multitype;

struct Vardesc {	/* for Namelist */
	char *name;
	char *addr;
	ftnlen *dims;
	int  type;
	};
typedef struct Vardesc Vardesc;

struct Namelist {
	char *name;
	Vardesc **vars;
	int nvars;
	};
typedef struct Namelist Namelist;

#define abs(x) ((x) >= 0 ? (x) : -(x))
#define dabs(x) (fabs(x))
#define f2cmin(a,b) ((a) <= (b) ? (a) : (b))
#define f2cmax(a,b) ((a) >= (b) ? (a) : (b))
#define dmin(a,b) (f2cmin(a,b))
#define dmax(a,b) (f2cmax(a,b))
#define bit_test(a,b)	((a) >> (b) & 1)
#define bit_clear(a,b)	((a) & ~((uinteger)1 << (b)))
#define bit_set(a,b)	((a) |  ((uinteger)1 << (b)))

#define abort_() { sig_die("Fortran abort routine called", 1); }
#define c_abs(z) (cabsf(Cf(z)))
#define c_cos(R,Z) { pCf(R)=ccos(Cf(Z)); }
#ifdef _MSC_VER
#define c_div(c, a, b) {Cf(c)._Val[0] = (Cf(a)._Val[0]/Cf(b)._Val[0]); Cf(c)._Val[1]=(Cf(a)._Val[1]/Cf(b)._Val[1]);}
#define z_div(c, a, b) {Cd(c)._Val[0] = (Cd(a)._Val[0]/Cd(b)._Val[0]); Cd(c)._Val[1]=(Cd(a)._Val[1]/df(b)._Val[1]);}
#else
#define c_div(c, a, b) {pCf(c) = Cf(a)/Cf(b);}
#define z_div(c, a, b) {pCd(c) = Cd(a)/Cd(b);}
#endif
#define c_exp(R, Z) {pCf(R) = cexpf(Cf(Z));}
#define c_log(R, Z) {pCf(R) = clogf(Cf(Z));}
#define c_sin(R, Z) {pCf(R) = csinf(Cf(Z));}
//#define c_sqrt(R, Z) {*(R) = csqrtf(Cf(Z));}
#define c_sqrt(R, Z) {pCf(R) = csqrtf(Cf(Z));}
#define d_abs(x) (fabs(*(x)))
#define d_acos(x) (acos(*(x)))
#define d_asin(x) (asin(*(x)))
#define d_atan(x) (atan(*(x)))
#define d_atn2(x, y) (atan2(*(x),*(y)))
#define d_cnjg(R, Z) { pCd(R) = conj(Cd(Z)); }
#define r_cnjg(R, Z) { pCf(R) = conjf(Cf(Z)); }
#define d_cos(x) (cos(*(x)))
#define d_cosh(x) (cosh(*(x)))
#define d_dim(__a, __b) ( *(__a) > *(__b) ? *(__a) - *(__b) : 0.0 )
#define d_exp(x) (exp(*(x)))
#define d_imag(z) (cimag(Cd(z)))
#define r_imag(z) (cimagf(Cf(z)))
#define d_int(__x) (*(__x)>0 ? floor(*(__x)) : -floor(- *(__x)))
#define r_int(__x) (*(__x)>0 ? floor(*(__x)) : -floor(- *(__x)))
#define d_lg10(x) ( 0.43429448190325182765 * log(*(x)) )
#define r_lg10(x) ( 0.43429448190325182765 * log(*(x)) )
#define d_log(x) (log(*(x)))
#define d_mod(x, y) (fmod(*(x), *(y)))
#define u_nint(__x) ((__x)>=0 ? floor((__x) + .5) : -floor(.5 - (__x)))
#define d_nint(x) u_nint(*(x))
#define u_sign(__a,__b) ((__b) >= 0 ? ((__a) >= 0 ? (__a) : -(__a)) : -((__a) >= 0 ? (__a) : -(__a)))
#define d_sign(a,b) u_sign(*(a),*(b))
#define r_sign(a,b) u_sign(*(a),*(b))
#define d_sin(x) (sin(*(x)))
#define d_sinh(x) (sinh(*(x)))
#define d_sqrt(x) (sqrt(*(x)))
#define d_tan(x) (tan(*(x)))
#define d_tanh(x) (tanh(*(x)))
#define i_abs(x) abs(*(x))
#define i_dnnt(x) ((integer)u_nint(*(x)))
#define i_len(s, n) (n)
#define i_nint(x) ((integer)u_nint(*(x)))
#define i_sign(a,b) ((integer)u_sign((integer)*(a),(integer)*(b)))
#define s_cat(lpp, rpp, rnp, np, llp) { 	ftnlen i, nc, ll; char *f__rp, *lp; 	ll = (llp); lp = (lpp); 	for(i=0; i < (int)*(np); ++i) {         	nc = ll; 	        if((rnp)[i] < nc) nc = (rnp)[i]; 	        ll -= nc;         	f__rp = (rpp)[i]; 	        while(--nc >= 0) *lp++ = *(f__rp)++;         } 	while(--ll >= 0) *lp++ = ' '; }
#define s_cmp(a,b,c,d) ((integer)strncmp((a),(b),f2cmin((c),(d))))
#define s_copy(A,B,C,D) { int __i,__m; for (__i=0, __m=f2cmin((C),(D)); __i<__m && (B)[__i] != 0; ++__i) (A)[__i] = (B)[__i]; }
#define sig_die(s, kill) { exit(1); }
#define s_stop(s, n) {exit(0);}
#define z_abs(z) (cabs(Cd(z)))
#define z_exp(R, Z) {pCd(R) = cexp(Cd(Z));}
#define z_sqrt(R, Z) {pCd(R) = csqrt(Cd(Z));}
#define myexit_() break;
#define mycycle() continue;
#define myceiling(w) {ceil(w)}
#define myhuge(w) {HUGE_VAL}
//#define mymaxloc_(w,s,e,n) {if (sizeof(*(w)) == sizeof(double)) dmaxloc_((w),*(s),*(e),n); else dmaxloc_((w),*(s),*(e),n);}
#define mymaxloc(w,s,e,n) {dmaxloc_(w,*(s),*(e),n)}

/*  -- translated by f2c (version 20000121).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/




/* Table of constant values */

static integer c__1 = 1;

/* > \brief <b> SGTSVX computes the solution to system of linear equations A * X = B for GT matrices </b> */

/*  =========== DOCUMENTATION =========== */

/* Online html documentation available at */
/*            http://www.netlib.org/lapack/explore-html/ */

/* > \htmlonly */
/* > Download SGTSVX + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/sgtsvx.
f"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/sgtsvx.
f"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/sgtsvx.
f"> */
/* > [TXT]</a> */
/* > \endhtmlonly */

/*  Definition: */
/*  =========== */

/*       SUBROUTINE SGTSVX( FACT, TRANS, N, NRHS, DL, D, DU, DLF, DF, DUF, */
/*                          DU2, IPIV, B, LDB, X, LDX, RCOND, FERR, BERR, */
/*                          WORK, IWORK, INFO ) */

/*       CHARACTER          FACT, TRANS */
/*       INTEGER            INFO, LDB, LDX, N, NRHS */
/*       REAL               RCOND */
/*       INTEGER            IPIV( * ), IWORK( * ) */
/*       REAL               B( LDB, * ), BERR( * ), D( * ), DF( * ), */
/*      $                   DL( * ), DLF( * ), DU( * ), DU2( * ), DUF( * ), */
/*      $                   FERR( * ), WORK( * ), X( LDX, * ) */


/* > \par Purpose: */
/*  ============= */
/* > */
/* > \verbatim */
/* > */
/* > SGTSVX uses the LU factorization to compute the solution to a real */
/* > system of linear equations A * X = B or A**T * X = B, */
/* > where A is a tridiagonal matrix of order N and X and B are N-by-NRHS */
/* > matrices. */
/* > */
/* > Error bounds on the solution and a condition estimate are also */
/* > provided. */
/* > \endverbatim */

/* > \par Description: */
/*  ================= */
/* > */
/* > \verbatim */
/* > */
/* > The following steps are performed: */
/* > */
/* > 1. If FACT = 'N', the LU decomposition is used to factor the matrix A */
/* >    as A = L * U, where L is a product of permutation and unit lower */
/* >    bidiagonal matrices and U is upper triangular with nonzeros in */
/* >    only the main diagonal and first two superdiagonals. */
/* > */
/* > 2. If some U(i,i)=0, so that U is exactly singular, then the routine */
/* >    returns with INFO = i. Otherwise, the factored form of A is used */
/* >    to estimate the condition number of the matrix A.  If the */
/* >    reciprocal of the condition number is less than machine precision, */
/* >    INFO = N+1 is returned as a warning, but the routine still goes on */
/* >    to solve for X and compute error bounds as described below. */
/* > */
/* > 3. The system of equations is solved for X using the factored form */
/* >    of A. */
/* > */
/* > 4. Iterative refinement is applied to improve the computed solution */
/* >    matrix and calculate error bounds and backward error estimates */
/* >    for it. */
/* > \endverbatim */

/*  Arguments: */
/*  ========== */

/* > \param[in] FACT */
/* > \verbatim */
/* >          FACT is CHARACTER*1 */
/* >          Specifies whether or not the factored form of A has been */
/* >          supplied on entry. */
/* >          = 'F':  DLF, DF, DUF, DU2, and IPIV contain the factored */
/* >                  form of A; DL, D, DU, DLF, DF, DUF, DU2 and IPIV */
/* >                  will not be modified. */
/* >          = 'N':  The matrix will be copied to DLF, DF, and DUF */
/* >                  and factored. */
/* > \endverbatim */
/* > */
/* > \param[in] TRANS */
/* > \verbatim */
/* >          TRANS is CHARACTER*1 */
/* >          Specifies the form of the system of equations: */
/* >          = 'N':  A * X = B     (No transpose) */
/* >          = 'T':  A**T * X = B  (Transpose) */
/* >          = 'C':  A**H * X = B  (Conjugate transpose = Transpose) */
/* > \endverbatim */
/* > */
/* > \param[in] N */
/* > \verbatim */
/* >          N is INTEGER */
/* >          The order of the matrix A.  N >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in] NRHS */
/* > \verbatim */
/* >          NRHS is INTEGER */
/* >          The number of right hand sides, i.e., the number of columns */
/* >          of the matrix B.  NRHS >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in] DL */
/* > \verbatim */
/* >          DL is REAL array, dimension (N-1) */
/* >          The (n-1) subdiagonal elements of A. */
/* > \endverbatim */
/* > */
/* > \param[in] D */
/* > \verbatim */
/* >          D is REAL array, dimension (N) */
/* >          The n diagonal elements of A. */
/* > \endverbatim */
/* > */
/* > \param[in] DU */
/* > \verbatim */
/* >          DU is REAL array, dimension (N-1) */
/* >          The (n-1) superdiagonal elements of A. */
/* > \endverbatim */
/* > */
/* > \param[in,out] DLF */
/* > \verbatim */
/* >          DLF is REAL array, dimension (N-1) */
/* >          If FACT = 'F', then DLF is an input argument and on entry */
/* >          contains the (n-1) multipliers that define the matrix L from */
/* >          the LU factorization of A as computed by SGTTRF. */
/* > */
/* >          If FACT = 'N', then DLF is an output argument and on exit */
/* >          contains the (n-1) multipliers that define the matrix L from */
/* >          the LU factorization of A. */
/* > \endverbatim */
/* > */
/* > \param[in,out] DF */
/* > \verbatim */
/* >          DF is REAL array, dimension (N) */
/* >          If FACT = 'F', then DF is an input argument and on entry */
/* >          contains the n diagonal elements of the upper triangular */
/* >          matrix U from the LU factorization of A. */
/* > */
/* >          If FACT = 'N', then DF is an output argument and on exit */
/* >          contains the n diagonal elements of the upper triangular */
/* >          matrix U from the LU factorization of A. */
/* > \endverbatim */
/* > */
/* > \param[in,out] DUF */
/* > \verbatim */
/* >          DUF is REAL array, dimension (N-1) */
/* >          If FACT = 'F', then DUF is an input argument and on entry */
/* >          contains the (n-1) elements of the first superdiagonal of U. */
/* > */
/* >          If FACT = 'N', then DUF is an output argument and on exit */
/* >          contains the (n-1) elements of the first superdiagonal of U. */
/* > \endverbatim */
/* > */
/* > \param[in,out] DU2 */
/* > \verbatim */
/* >          DU2 is REAL array, dimension (N-2) */
/* >          If FACT = 'F', then DU2 is an input argument and on entry */
/* >          contains the (n-2) elements of the second superdiagonal of */
/* >          U. */
/* > */
/* >          If FACT = 'N', then DU2 is an output argument and on exit */
/* >          contains the (n-2) elements of the second superdiagonal of */
/* >          U. */
/* > \endverbatim */
/* > */
/* > \param[in,out] IPIV */
/* > \verbatim */
/* >          IPIV is INTEGER array, dimension (N) */
/* >          If FACT = 'F', then IPIV is an input argument and on entry */
/* >          contains the pivot indices from the LU factorization of A as */
/* >          computed by SGTTRF. */
/* > */
/* >          If FACT = 'N', then IPIV is an output argument and on exit */
/* >          contains the pivot indices from the LU factorization of A; */
/* >          row i of the matrix was interchanged with row IPIV(i). */
/* >          IPIV(i) will always be either i or i+1; IPIV(i) = i indicates */
/* >          a row interchange was not required. */
/* > \endverbatim */
/* > */
/* > \param[in] B */
/* > \verbatim */
/* >          B is REAL array, dimension (LDB,NRHS) */
/* >          The N-by-NRHS right hand side matrix B. */
/* > \endverbatim */
/* > */
/* > \param[in] LDB */
/* > \verbatim */
/* >          LDB is INTEGER */
/* >          The leading dimension of the array B.  LDB >= f2cmax(1,N). */
/* > \endverbatim */
/* > */
/* > \param[out] X */
/* > \verbatim */
/* >          X is REAL array, dimension (LDX,NRHS) */
/* >          If INFO = 0 or INFO = N+1, the N-by-NRHS solution matrix X. */
/* > \endverbatim */
/* > */
/* > \param[in] LDX */
/* > \verbatim */
/* >          LDX is INTEGER */
/* >          The leading dimension of the array X.  LDX >= f2cmax(1,N). */
/* > \endverbatim */
/* > */
/* > \param[out] RCOND */
/* > \verbatim */
/* >          RCOND is REAL */
/* >          The estimate of the reciprocal condition number of the matrix */
/* >          A.  If RCOND is less than the machine precision (in */
/* >          particular, if RCOND = 0), the matrix is singular to working */
/* >          precision.  This condition is indicated by a return code of */
/* >          INFO > 0. */
/* > \endverbatim */
/* > */
/* > \param[out] FERR */
/* > \verbatim */
/* >          FERR is REAL array, dimension (NRHS) */
/* >          The estimated forward error bound for each solution vector */
/* >          X(j) (the j-th column of the solution matrix X). */
/* >          If XTRUE is the true solution corresponding to X(j), FERR(j) */
/* >          is an estimated upper bound for the magnitude of the largest */
/* >          element in (X(j) - XTRUE) divided by the magnitude of the */
/* >          largest element in X(j).  The estimate is as reliable as */
/* >          the estimate for RCOND, and is almost always a slight */
/* >          overestimate of the true error. */
/* > \endverbatim */
/* > */
/* > \param[out] BERR */
/* > \verbatim */
/* >          BERR is REAL array, dimension (NRHS) */
/* >          The componentwise relative backward error of each solution */
/* >          vector X(j) (i.e., the smallest relative change in */
/* >          any element of A or B that makes X(j) an exact solution). */
/* > \endverbatim */
/* > */
/* > \param[out] WORK */
/* > \verbatim */
/* >          WORK is REAL array, dimension (3*N) */
/* > \endverbatim */
/* > */
/* > \param[out] IWORK */
/* > \verbatim */
/* >          IWORK is INTEGER array, dimension (N) */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* >          INFO is INTEGER */
/* >          = 0:  successful exit */
/* >          < 0:  if INFO = -i, the i-th argument had an illegal value */
/* >          > 0:  if INFO = i, and i is */
/* >                <= N:  U(i,i) is exactly zero.  The factorization */
/* >                       has not been completed unless i = N, but the */
/* >                       factor U is exactly singular, so the solution */
/* >                       and error bounds could not be computed. */
/* >                       RCOND = 0 is returned. */
/* >                = N+1: U is nonsingular, but RCOND is less than machine */
/* >                       precision, meaning that the matrix is singular */
/* >                       to working precision.  Nevertheless, the */
/* >                       solution and error bounds are computed because */
/* >                       there are a number of situations where the */
/* >                       computed solution can be more accurate than the */
/* >                       value of RCOND would suggest. */
/* > \endverbatim */

/*  Authors: */
/*  ======== */

/* > \author Univ. of Tennessee */
/* > \author Univ. of California Berkeley */
/* > \author Univ. of Colorado Denver */
/* > \author NAG Ltd. */

/* > \date December 2016 */

/* > \ingroup realGTsolve */

/*  ===================================================================== */
/* Subroutine */ void sgtsvx_(char *fact, char *trans, integer *n, integer *
	nrhs, real *dl, real *d__, real *du, real *dlf, real *df, real *duf, 
	real *du2, integer *ipiv, real *b, integer *ldb, real *x, integer *
	ldx, real *rcond, real *ferr, real *berr, real *work, integer *iwork, 
	integer *info)
{
    /* System generated locals */
    integer b_dim1, b_offset, x_dim1, x_offset, i__1;

    /* Local variables */
    char norm[1];
    extern logical lsame_(char *, char *);
    real anorm;
    extern /* Subroutine */ void scopy_(integer *, real *, integer *, real *, 
	    integer *);
    extern real slamch_(char *);
    logical nofact;
    extern /* Subroutine */ int xerbla_(char *, integer *, ftnlen);
    extern real slangt_(char *, integer *, real *, real *, real *);
    extern /* Subroutine */ void slacpy_(char *, integer *, integer *, real *, 
	    integer *, real *, integer *), sgtcon_(char *, integer *, 
	    real *, real *, real *, real *, integer *, real *, real *, real *,
	     integer *, integer *);
    logical notran;
    extern /* Subroutine */ void sgtrfs_(char *, integer *, integer *, real *, 
	    real *, real *, real *, real *, real *, real *, integer *, real *,
	     integer *, real *, integer *, real *, real *, real *, integer *, 
	    integer *), sgttrf_(integer *, real *, real *, real *, 
	    real *, integer *, integer *), sgttrs_(char *, integer *, integer 
	    *, real *, real *, real *, real *, integer *, real *, integer *, 
	    integer *);


/*  -- LAPACK driver routine (version 3.7.0) -- */
/*  -- LAPACK is a software package provided by Univ. of Tennessee,    -- */
/*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
/*     December 2016 */


/*  ===================================================================== */


    /* Parameter adjustments */
    --dl;
    --d__;
    --du;
    --dlf;
    --df;
    --duf;
    --du2;
    --ipiv;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;
    x_dim1 = *ldx;
    x_offset = 1 + x_dim1 * 1;
    x -= x_offset;
    --ferr;
    --berr;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;
    nofact = lsame_(fact, "N");
    notran = lsame_(trans, "N");
    if (! nofact && ! lsame_(fact, "F")) {
	*info = -1;
    } else if (! notran && ! lsame_(trans, "T") && ! 
	    lsame_(trans, "C")) {
	*info = -2;
    } else if (*n < 0) {
	*info = -3;
    } else if (*nrhs < 0) {
	*info = -4;
    } else if (*ldb < f2cmax(1,*n)) {
	*info = -14;
    } else if (*ldx < f2cmax(1,*n)) {
	*info = -16;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("SGTSVX", &i__1, (ftnlen)6);
	return;
    }

    if (nofact) {

/*        Compute the LU factorization of A. */

	scopy_(n, &d__[1], &c__1, &df[1], &c__1);
	if (*n > 1) {
	    i__1 = *n - 1;
	    scopy_(&i__1, &dl[1], &c__1, &dlf[1], &c__1);
	    i__1 = *n - 1;
	    scopy_(&i__1, &du[1], &c__1, &duf[1], &c__1);
	}
	sgttrf_(n, &dlf[1], &df[1], &duf[1], &du2[1], &ipiv[1], info);

/*        Return if INFO is non-zero. */

	if (*info > 0) {
	    *rcond = 0.f;
	    return;
	}
    }

/*     Compute the norm of the matrix A. */

    if (notran) {
	*(unsigned char *)norm = '1';
    } else {
	*(unsigned char *)norm = 'I';
    }
    anorm = slangt_(norm, n, &dl[1], &d__[1], &du[1]);

/*     Compute the reciprocal of the condition number of A. */

    sgtcon_(norm, n, &dlf[1], &df[1], &duf[1], &du2[1], &ipiv[1], &anorm, 
	    rcond, &work[1], &iwork[1], info);

/*     Compute the solution vectors X. */

    slacpy_("Full", n, nrhs, &b[b_offset], ldb, &x[x_offset], ldx);
    sgttrs_(trans, n, nrhs, &dlf[1], &df[1], &duf[1], &du2[1], &ipiv[1], &x[
	    x_offset], ldx, info);

/*     Use iterative refinement to improve the computed solutions and */
/*     compute error bounds and backward error estimates for them. */

    sgtrfs_(trans, n, nrhs, &dl[1], &d__[1], &du[1], &dlf[1], &df[1], &duf[1],
	     &du2[1], &ipiv[1], &b[b_offset], ldb, &x[x_offset], ldx, &ferr[1]
	    , &berr[1], &work[1], &iwork[1], info);

/*     Set INFO = N+1 if the matrix is singular to working precision. */

    if (*rcond < slamch_("Epsilon")) {
	*info = *n + 1;
    }

    return;

/*     End of SGTSVX */

} /* sgtsvx_ */