OpenBLAS/lapack-netlib/SRC/dlasy2.c

/* f2c.h  --  Standard Fortran to C header file */

/**  barf  [ba:rf]  2.  "He suggested using FORTRAN, and everybody barfed."

	- From The Shogakukan DICTIONARY OF NEW ENGLISH (Second edition) */

#ifndef F2C_INCLUDE
#define F2C_INCLUDE

#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;
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;}
#define pCf(z) (*_pCf(z))
#define pCd(z) (*_pCd(z))
typedef int logical;
typedef short int shortlogical;
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)); }
#define c_div(c, a, b) {pCf(c) = Cf(a)/Cf(b);}
#define z_div(c, a, b) {pCd(c) = Cd(a)/Cd(b);}
#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) = conj(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) (cimag(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 pow_dd(ap, bp) ( pow(*(ap), *(bp)))
#define pow_si(B,E) spow_ui(*(B),*(E))
#define pow_ri(B,E) spow_ui(*(B),*(E))
#define pow_di(B,E) dpow_ui(*(B),*(E))
#define pow_zi(p, a, b) {pCd(p) = zpow_ui(Cd(a), *(b));}
#define pow_ci(p, a, b) {pCf(p) = cpow_ui(Cf(a), *(b));}
#define pow_zz(R,A,B) {pCd(R) = cpow(Cd(A),*(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);}
static char junk[] = "\n@(#)LIBF77 VERSION 19990503\n";
#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)}

/* procedure parameter types for -A and -C++ */

#define F2C_proc_par_types 1
#ifdef __cplusplus
typedef logical (*L_fp)(...);
#else
typedef logical (*L_fp)();
#endif

static float spow_ui(float x, integer n) {
	float pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static double dpow_ui(double x, integer n) {
	double pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static _Complex float cpow_ui(_Complex float x, integer n) {
	_Complex float pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static _Complex double zpow_ui(_Complex double x, integer n) {
	_Complex double pow=1.0; unsigned long int u;
	if(n != 0) {
		if(n < 0) n = -n, x = 1/x;
		for(u = n; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static integer pow_ii(integer x, integer n) {
	integer pow; unsigned long int u;
	if (n <= 0) {
		if (n == 0 || x == 1) pow = 1;
		else if (x != -1) pow = x == 0 ? 1/x : 0;
		else n = -n;
	}
	if ((n > 0) || !(n == 0 || x == 1 || x != -1)) {
		u = n;
		for(pow = 1; ; ) {
			if(u & 01) pow *= x;
			if(u >>= 1) x *= x;
			else break;
		}
	}
	return pow;
}
static integer dmaxloc_(double *w, integer s, integer e, integer *n)
{
	double m; integer i, mi;
	for(m=w[s-1], mi=s, i=s+1; i<=e; i++)
		if (w[i-1]>m) mi=i ,m=w[i-1];
	return mi-s+1;
}
static integer smaxloc_(float *w, integer s, integer e, integer *n)
{
	float m; integer i, mi;
	for(m=w[s-1], mi=s, i=s+1; i<=e; i++)
		if (w[i-1]>m) mi=i ,m=w[i-1];
	return mi-s+1;
}
static inline void cdotc_(complex *z, integer *n_, complex *x, integer *incx_, complex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex float zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conjf(Cf(&x[i])) * Cf(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conjf(Cf(&x[i*incx])) * Cf(&y[i*incy]);
		}
	}
	pCf(z) = zdotc;
}
static inline void zdotc_(doublecomplex *z, integer *n_, doublecomplex *x, integer *incx_, doublecomplex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex double zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conj(Cd(&x[i])) * Cd(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += conj(Cd(&x[i*incx])) * Cd(&y[i*incy]);
		}
	}
	pCd(z) = zdotc;
}	
static inline void cdotu_(complex *z, integer *n_, complex *x, integer *incx_, complex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex float zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cf(&x[i]) * Cf(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cf(&x[i*incx]) * Cf(&y[i*incy]);
		}
	}
	pCf(z) = zdotc;
}
static inline void zdotu_(doublecomplex *z, integer *n_, doublecomplex *x, integer *incx_, doublecomplex *y, integer *incy_) {
	integer n = *n_, incx = *incx_, incy = *incy_, i;
	_Complex double zdotc = 0.0;
	if (incx == 1 && incy == 1) {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cd(&x[i]) * Cd(&y[i]);
		}
	} else {
		for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
			zdotc += Cd(&x[i*incx]) * Cd(&y[i*incy]);
		}
	}
	pCd(z) = zdotc;
}
#endif
/*  -- 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__4 = 4;
static integer c__1 = 1;
static integer c__16 = 16;
static integer c__0 = 0;

/* > \brief \b DLASY2 solves the Sylvester matrix equation where the matrices are of order 1 or 2. */

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

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

/* > \htmlonly */
/* > Download DLASY2 + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasy2.
f"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlasy2.
f"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasy2.
f"> */
/* > [TXT]</a> */
/* > \endhtmlonly */

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

/*       SUBROUTINE DLASY2( LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR, */
/*                          LDTR, B, LDB, SCALE, X, LDX, XNORM, INFO ) */

/*       LOGICAL            LTRANL, LTRANR */
/*       INTEGER            INFO, ISGN, LDB, LDTL, LDTR, LDX, N1, N2 */
/*       DOUBLE PRECISION   SCALE, XNORM */
/*       DOUBLE PRECISION   B( LDB, * ), TL( LDTL, * ), TR( LDTR, * ), */
/*      $                   X( LDX, * ) */


/* > \par Purpose: */
/*  ============= */
/* > */
/* > \verbatim */
/* > */
/* > DLASY2 solves for the N1 by N2 matrix X, 1 <= N1,N2 <= 2, in */
/* > */
/* >        op(TL)*X + ISGN*X*op(TR) = SCALE*B, */
/* > */
/* > where TL is N1 by N1, TR is N2 by N2, B is N1 by N2, and ISGN = 1 or */
/* > -1.  op(T) = T or T**T, where T**T denotes the transpose of T. */
/* > \endverbatim */

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

/* > \param[in] LTRANL */
/* > \verbatim */
/* >          LTRANL is LOGICAL */
/* >          On entry, LTRANL specifies the op(TL): */
/* >             = .FALSE., op(TL) = TL, */
/* >             = .TRUE., op(TL) = TL**T. */
/* > \endverbatim */
/* > */
/* > \param[in] LTRANR */
/* > \verbatim */
/* >          LTRANR is LOGICAL */
/* >          On entry, LTRANR specifies the op(TR): */
/* >            = .FALSE., op(TR) = TR, */
/* >            = .TRUE., op(TR) = TR**T. */
/* > \endverbatim */
/* > */
/* > \param[in] ISGN */
/* > \verbatim */
/* >          ISGN is INTEGER */
/* >          On entry, ISGN specifies the sign of the equation */
/* >          as described before. ISGN may only be 1 or -1. */
/* > \endverbatim */
/* > */
/* > \param[in] N1 */
/* > \verbatim */
/* >          N1 is INTEGER */
/* >          On entry, N1 specifies the order of matrix TL. */
/* >          N1 may only be 0, 1 or 2. */
/* > \endverbatim */
/* > */
/* > \param[in] N2 */
/* > \verbatim */
/* >          N2 is INTEGER */
/* >          On entry, N2 specifies the order of matrix TR. */
/* >          N2 may only be 0, 1 or 2. */
/* > \endverbatim */
/* > */
/* > \param[in] TL */
/* > \verbatim */
/* >          TL is DOUBLE PRECISION array, dimension (LDTL,2) */
/* >          On entry, TL contains an N1 by N1 matrix. */
/* > \endverbatim */
/* > */
/* > \param[in] LDTL */
/* > \verbatim */
/* >          LDTL is INTEGER */
/* >          The leading dimension of the matrix TL. LDTL >= f2cmax(1,N1). */
/* > \endverbatim */
/* > */
/* > \param[in] TR */
/* > \verbatim */
/* >          TR is DOUBLE PRECISION array, dimension (LDTR,2) */
/* >          On entry, TR contains an N2 by N2 matrix. */
/* > \endverbatim */
/* > */
/* > \param[in] LDTR */
/* > \verbatim */
/* >          LDTR is INTEGER */
/* >          The leading dimension of the matrix TR. LDTR >= f2cmax(1,N2). */
/* > \endverbatim */
/* > */
/* > \param[in] B */
/* > \verbatim */
/* >          B is DOUBLE PRECISION array, dimension (LDB,2) */
/* >          On entry, the N1 by N2 matrix B contains the right-hand */
/* >          side of the equation. */
/* > \endverbatim */
/* > */
/* > \param[in] LDB */
/* > \verbatim */
/* >          LDB is INTEGER */
/* >          The leading dimension of the matrix B. LDB >= f2cmax(1,N1). */
/* > \endverbatim */
/* > */
/* > \param[out] SCALE */
/* > \verbatim */
/* >          SCALE is DOUBLE PRECISION */
/* >          On exit, SCALE contains the scale factor. SCALE is chosen */
/* >          less than or equal to 1 to prevent the solution overflowing. */
/* > \endverbatim */
/* > */
/* > \param[out] X */
/* > \verbatim */
/* >          X is DOUBLE PRECISION array, dimension (LDX,2) */
/* >          On exit, X contains the N1 by N2 solution. */
/* > \endverbatim */
/* > */
/* > \param[in] LDX */
/* > \verbatim */
/* >          LDX is INTEGER */
/* >          The leading dimension of the matrix X. LDX >= f2cmax(1,N1). */
/* > \endverbatim */
/* > */
/* > \param[out] XNORM */
/* > \verbatim */
/* >          XNORM is DOUBLE PRECISION */
/* >          On exit, XNORM is the infinity-norm of the solution. */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* >          INFO is INTEGER */
/* >          On exit, INFO is set to */
/* >             0: successful exit. */
/* >             1: TL and TR have too close eigenvalues, so TL or */
/* >                TR is perturbed to get a nonsingular equation. */
/* >          NOTE: In the interests of speed, this routine does not */
/* >                check the inputs for errors. */
/* > \endverbatim */

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

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

/* > \date June 2016 */

/* > \ingroup doubleSYauxiliary */

/*  ===================================================================== */
/* Subroutine */ int dlasy2_(logical *ltranl, logical *ltranr, integer *isgn, 
	integer *n1, integer *n2, doublereal *tl, integer *ldtl, doublereal *
	tr, integer *ldtr, doublereal *b, integer *ldb, doublereal *scale, 
	doublereal *x, integer *ldx, doublereal *xnorm, integer *info)
{
    /* Initialized data */

    static integer locu12[4] = { 3,4,1,2 };
    static integer locl21[4] = { 2,1,4,3 };
    static integer locu22[4] = { 4,3,2,1 };
    static logical xswpiv[4] = { FALSE_,FALSE_,TRUE_,TRUE_ };
    static logical bswpiv[4] = { FALSE_,TRUE_,FALSE_,TRUE_ };

    /* System generated locals */
    integer b_dim1, b_offset, tl_dim1, tl_offset, tr_dim1, tr_offset, x_dim1, 
	    x_offset;
    doublereal d__1, d__2, d__3, d__4, d__5, d__6, d__7, d__8;

    /* Local variables */
    doublereal btmp[4], smin;
    integer ipiv;
    doublereal temp;
    integer jpiv[4];
    doublereal xmax;
    integer ipsv, jpsv, i__, j, k;
    logical bswap;
    extern /* Subroutine */ int dcopy_(integer *, doublereal *, integer *, 
	    doublereal *, integer *), dswap_(integer *, doublereal *, integer 
	    *, doublereal *, integer *);
    logical xswap;
    doublereal x2[2], l21, u11, u12;
    integer ip, jp;
    doublereal u22, t16[16]	/* was [4][4] */;
    extern doublereal dlamch_(char *);
    extern integer idamax_(integer *, doublereal *, integer *);
    doublereal smlnum, gam, bet, eps, sgn, tmp[4], tau1;


/*  -- LAPACK auxiliary 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..-- */
/*     June 2016 */


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

    /* Parameter adjustments */
    tl_dim1 = *ldtl;
    tl_offset = 1 + tl_dim1 * 1;
    tl -= tl_offset;
    tr_dim1 = *ldtr;
    tr_offset = 1 + tr_dim1 * 1;
    tr -= tr_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;
    x_dim1 = *ldx;
    x_offset = 1 + x_dim1 * 1;
    x -= x_offset;

    /* Function Body */

/*     Do not check the input parameters for errors */

    *info = 0;

/*     Quick return if possible */

    if (*n1 == 0 || *n2 == 0) {
	return 0;
    }

/*     Set constants to control overflow */

    eps = dlamch_("P");
    smlnum = dlamch_("S") / eps;
    sgn = (doublereal) (*isgn);

    k = *n1 + *n1 + *n2 - 2;
    switch (k) {
	case 1:  goto L10;
	case 2:  goto L20;
	case 3:  goto L30;
	case 4:  goto L50;
    }

/*     1 by 1: TL11*X + SGN*X*TR11 = B11 */

L10:
    tau1 = tl[tl_dim1 + 1] + sgn * tr[tr_dim1 + 1];
    bet = abs(tau1);
    if (bet <= smlnum) {
	tau1 = smlnum;
	bet = smlnum;
	*info = 1;
    }

    *scale = 1.;
    gam = (d__1 = b[b_dim1 + 1], abs(d__1));
    if (smlnum * gam > bet) {
	*scale = 1. / gam;
    }

    x[x_dim1 + 1] = b[b_dim1 + 1] * *scale / tau1;
    *xnorm = (d__1 = x[x_dim1 + 1], abs(d__1));
    return 0;

/*     1 by 2: */
/*     TL11*[X11 X12] + ISGN*[X11 X12]*op[TR11 TR12]  = [B11 B12] */
/*                                       [TR21 TR22] */

L20:

/* Computing MAX */
/* Computing MAX */
    d__7 = (d__1 = tl[tl_dim1 + 1], abs(d__1)), d__8 = (d__2 = tr[tr_dim1 + 1]
	    , abs(d__2)), d__7 = f2cmax(d__7,d__8), d__8 = (d__3 = tr[(tr_dim1 <<
	     1) + 1], abs(d__3)), d__7 = f2cmax(d__7,d__8), d__8 = (d__4 = tr[
	    tr_dim1 + 2], abs(d__4)), d__7 = f2cmax(d__7,d__8), d__8 = (d__5 = 
	    tr[(tr_dim1 << 1) + 2], abs(d__5));
    d__6 = eps * f2cmax(d__7,d__8);
    smin = f2cmax(d__6,smlnum);
    tmp[0] = tl[tl_dim1 + 1] + sgn * tr[tr_dim1 + 1];
    tmp[3] = tl[tl_dim1 + 1] + sgn * tr[(tr_dim1 << 1) + 2];
    if (*ltranr) {
	tmp[1] = sgn * tr[tr_dim1 + 2];
	tmp[2] = sgn * tr[(tr_dim1 << 1) + 1];
    } else {
	tmp[1] = sgn * tr[(tr_dim1 << 1) + 1];
	tmp[2] = sgn * tr[tr_dim1 + 2];
    }
    btmp[0] = b[b_dim1 + 1];
    btmp[1] = b[(b_dim1 << 1) + 1];
    goto L40;

/*     2 by 1: */
/*          op[TL11 TL12]*[X11] + ISGN* [X11]*TR11  = [B11] */
/*            [TL21 TL22] [X21]         [X21]         [B21] */

L30:
/* Computing MAX */
/* Computing MAX */
    d__7 = (d__1 = tr[tr_dim1 + 1], abs(d__1)), d__8 = (d__2 = tl[tl_dim1 + 1]
	    , abs(d__2)), d__7 = f2cmax(d__7,d__8), d__8 = (d__3 = tl[(tl_dim1 <<
	     1) + 1], abs(d__3)), d__7 = f2cmax(d__7,d__8), d__8 = (d__4 = tl[
	    tl_dim1 + 2], abs(d__4)), d__7 = f2cmax(d__7,d__8), d__8 = (d__5 = 
	    tl[(tl_dim1 << 1) + 2], abs(d__5));
    d__6 = eps * f2cmax(d__7,d__8);
    smin = f2cmax(d__6,smlnum);
    tmp[0] = tl[tl_dim1 + 1] + sgn * tr[tr_dim1 + 1];
    tmp[3] = tl[(tl_dim1 << 1) + 2] + sgn * tr[tr_dim1 + 1];
    if (*ltranl) {
	tmp[1] = tl[(tl_dim1 << 1) + 1];
	tmp[2] = tl[tl_dim1 + 2];
    } else {
	tmp[1] = tl[tl_dim1 + 2];
	tmp[2] = tl[(tl_dim1 << 1) + 1];
    }
    btmp[0] = b[b_dim1 + 1];
    btmp[1] = b[b_dim1 + 2];
L40:

/*     Solve 2 by 2 system using complete pivoting. */
/*     Set pivots less than SMIN to SMIN. */

    ipiv = idamax_(&c__4, tmp, &c__1);
    u11 = tmp[ipiv - 1];
    if (abs(u11) <= smin) {
	*info = 1;
	u11 = smin;
    }
    u12 = tmp[locu12[ipiv - 1] - 1];
    l21 = tmp[locl21[ipiv - 1] - 1] / u11;
    u22 = tmp[locu22[ipiv - 1] - 1] - u12 * l21;
    xswap = xswpiv[ipiv - 1];
    bswap = bswpiv[ipiv - 1];
    if (abs(u22) <= smin) {
	*info = 1;
	u22 = smin;
    }
    if (bswap) {
	temp = btmp[1];
	btmp[1] = btmp[0] - l21 * temp;
	btmp[0] = temp;
    } else {
	btmp[1] -= l21 * btmp[0];
    }
    *scale = 1.;
    if (smlnum * 2. * abs(btmp[1]) > abs(u22) || smlnum * 2. * abs(btmp[0]) > 
	    abs(u11)) {
/* Computing MAX */
	d__1 = abs(btmp[0]), d__2 = abs(btmp[1]);
	*scale = .5 / f2cmax(d__1,d__2);
	btmp[0] *= *scale;
	btmp[1] *= *scale;
    }
    x2[1] = btmp[1] / u22;
    x2[0] = btmp[0] / u11 - u12 / u11 * x2[1];
    if (xswap) {
	temp = x2[1];
	x2[1] = x2[0];
	x2[0] = temp;
    }
    x[x_dim1 + 1] = x2[0];
    if (*n1 == 1) {
	x[(x_dim1 << 1) + 1] = x2[1];
	*xnorm = (d__1 = x[x_dim1 + 1], abs(d__1)) + (d__2 = x[(x_dim1 << 1) 
		+ 1], abs(d__2));
    } else {
	x[x_dim1 + 2] = x2[1];
/* Computing MAX */
	d__3 = (d__1 = x[x_dim1 + 1], abs(d__1)), d__4 = (d__2 = x[x_dim1 + 2]
		, abs(d__2));
	*xnorm = f2cmax(d__3,d__4);
    }
    return 0;

/*     2 by 2: */
/*     op[TL11 TL12]*[X11 X12] +ISGN* [X11 X12]*op[TR11 TR12] = [B11 B12] */
/*       [TL21 TL22] [X21 X22]        [X21 X22]   [TR21 TR22]   [B21 B22] */

/*     Solve equivalent 4 by 4 system using complete pivoting. */
/*     Set pivots less than SMIN to SMIN. */

L50:
/* Computing MAX */
    d__5 = (d__1 = tr[tr_dim1 + 1], abs(d__1)), d__6 = (d__2 = tr[(tr_dim1 << 
	    1) + 1], abs(d__2)), d__5 = f2cmax(d__5,d__6), d__6 = (d__3 = tr[
	    tr_dim1 + 2], abs(d__3)), d__5 = f2cmax(d__5,d__6), d__6 = (d__4 = 
	    tr[(tr_dim1 << 1) + 2], abs(d__4));
    smin = f2cmax(d__5,d__6);
/* Computing MAX */
    d__5 = smin, d__6 = (d__1 = tl[tl_dim1 + 1], abs(d__1)), d__5 = f2cmax(d__5,
	    d__6), d__6 = (d__2 = tl[(tl_dim1 << 1) + 1], abs(d__2)), d__5 = 
	    f2cmax(d__5,d__6), d__6 = (d__3 = tl[tl_dim1 + 2], abs(d__3)), d__5 =
	     f2cmax(d__5,d__6), d__6 = (d__4 = tl[(tl_dim1 << 1) + 2], abs(d__4))
	    ;
    smin = f2cmax(d__5,d__6);
/* Computing MAX */
    d__1 = eps * smin;
    smin = f2cmax(d__1,smlnum);
    btmp[0] = 0.;
    dcopy_(&c__16, btmp, &c__0, t16, &c__1);
    t16[0] = tl[tl_dim1 + 1] + sgn * tr[tr_dim1 + 1];
    t16[5] = tl[(tl_dim1 << 1) + 2] + sgn * tr[tr_dim1 + 1];
    t16[10] = tl[tl_dim1 + 1] + sgn * tr[(tr_dim1 << 1) + 2];
    t16[15] = tl[(tl_dim1 << 1) + 2] + sgn * tr[(tr_dim1 << 1) + 2];
    if (*ltranl) {
	t16[4] = tl[tl_dim1 + 2];
	t16[1] = tl[(tl_dim1 << 1) + 1];
	t16[14] = tl[tl_dim1 + 2];
	t16[11] = tl[(tl_dim1 << 1) + 1];
    } else {
	t16[4] = tl[(tl_dim1 << 1) + 1];
	t16[1] = tl[tl_dim1 + 2];
	t16[14] = tl[(tl_dim1 << 1) + 1];
	t16[11] = tl[tl_dim1 + 2];
    }
    if (*ltranr) {
	t16[8] = sgn * tr[(tr_dim1 << 1) + 1];
	t16[13] = sgn * tr[(tr_dim1 << 1) + 1];
	t16[2] = sgn * tr[tr_dim1 + 2];
	t16[7] = sgn * tr[tr_dim1 + 2];
    } else {
	t16[8] = sgn * tr[tr_dim1 + 2];
	t16[13] = sgn * tr[tr_dim1 + 2];
	t16[2] = sgn * tr[(tr_dim1 << 1) + 1];
	t16[7] = sgn * tr[(tr_dim1 << 1) + 1];
    }
    btmp[0] = b[b_dim1 + 1];
    btmp[1] = b[b_dim1 + 2];
    btmp[2] = b[(b_dim1 << 1) + 1];
    btmp[3] = b[(b_dim1 << 1) + 2];

/*     Perform elimination */

    for (i__ = 1; i__ <= 3; ++i__) {
	xmax = 0.;
	for (ip = i__; ip <= 4; ++ip) {
	    for (jp = i__; jp <= 4; ++jp) {
		if ((d__1 = t16[ip + (jp << 2) - 5], abs(d__1)) >= xmax) {
		    xmax = (d__1 = t16[ip + (jp << 2) - 5], abs(d__1));
		    ipsv = ip;
		    jpsv = jp;
		}
/* L60: */
	    }
/* L70: */
	}
	if (ipsv != i__) {
	    dswap_(&c__4, &t16[ipsv - 1], &c__4, &t16[i__ - 1], &c__4);
	    temp = btmp[i__ - 1];
	    btmp[i__ - 1] = btmp[ipsv - 1];
	    btmp[ipsv - 1] = temp;
	}
	if (jpsv != i__) {
	    dswap_(&c__4, &t16[(jpsv << 2) - 4], &c__1, &t16[(i__ << 2) - 4], 
		    &c__1);
	}
	jpiv[i__ - 1] = jpsv;
	if ((d__1 = t16[i__ + (i__ << 2) - 5], abs(d__1)) < smin) {
	    *info = 1;
	    t16[i__ + (i__ << 2) - 5] = smin;
	}
	for (j = i__ + 1; j <= 4; ++j) {
	    t16[j + (i__ << 2) - 5] /= t16[i__ + (i__ << 2) - 5];
	    btmp[j - 1] -= t16[j + (i__ << 2) - 5] * btmp[i__ - 1];
	    for (k = i__ + 1; k <= 4; ++k) {
		t16[j + (k << 2) - 5] -= t16[j + (i__ << 2) - 5] * t16[i__ + (
			k << 2) - 5];
/* L80: */
	    }
/* L90: */
	}
/* L100: */
    }
    if (abs(t16[15]) < smin) {
	*info = 1;
	t16[15] = smin;
    }
    *scale = 1.;
    if (smlnum * 8. * abs(btmp[0]) > abs(t16[0]) || smlnum * 8. * abs(btmp[1])
	     > abs(t16[5]) || smlnum * 8. * abs(btmp[2]) > abs(t16[10]) || 
	    smlnum * 8. * abs(btmp[3]) > abs(t16[15])) {
/* Computing MAX */
	d__1 = abs(btmp[0]), d__2 = abs(btmp[1]), d__1 = f2cmax(d__1,d__2), d__2 
		= abs(btmp[2]), d__1 = f2cmax(d__1,d__2), d__2 = abs(btmp[3]);
	*scale = .125 / f2cmax(d__1,d__2);
	btmp[0] *= *scale;
	btmp[1] *= *scale;
	btmp[2] *= *scale;
	btmp[3] *= *scale;
    }
    for (i__ = 1; i__ <= 4; ++i__) {
	k = 5 - i__;
	temp = 1. / t16[k + (k << 2) - 5];
	tmp[k - 1] = btmp[k - 1] * temp;
	for (j = k + 1; j <= 4; ++j) {
	    tmp[k - 1] -= temp * t16[k + (j << 2) - 5] * tmp[j - 1];
/* L110: */
	}
/* L120: */
    }
    for (i__ = 1; i__ <= 3; ++i__) {
	if (jpiv[4 - i__ - 1] != 4 - i__) {
	    temp = tmp[4 - i__ - 1];
	    tmp[4 - i__ - 1] = tmp[jpiv[4 - i__ - 1] - 1];
	    tmp[jpiv[4 - i__ - 1] - 1] = temp;
	}
/* L130: */
    }
    x[x_dim1 + 1] = tmp[0];
    x[x_dim1 + 2] = tmp[1];
    x[(x_dim1 << 1) + 1] = tmp[2];
    x[(x_dim1 << 1) + 2] = tmp[3];
/* Computing MAX */
    d__1 = abs(tmp[0]) + abs(tmp[2]), d__2 = abs(tmp[1]) + abs(tmp[3]);
    *xnorm = f2cmax(d__1,d__2);
    return 0;

/*     End of DLASY2 */

} /* dlasy2_ */