OpenBLAS/lapack-netlib/SRC/slag2.c

920 lines
26 KiB
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 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++ */
#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;
}
#ifdef _MSC_VER
static _Fcomplex cpow_ui(complex x, integer n) {
complex pow={1.0,0.0}; unsigned long int u;
if(n != 0) {
if(n < 0) n = -n, x.r = 1/x.r, x.i=1/x.i;
for(u = n; ; ) {
if(u & 01) pow.r *= x.r, pow.i *= x.i;
if(u >>= 1) x.r *= x.r, x.i *= x.i;
else break;
}
}
_Fcomplex p={pow.r, pow.i};
return p;
}
#else
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;
}
#endif
#ifdef _MSC_VER
static _Dcomplex zpow_ui(_Dcomplex x, integer n) {
_Dcomplex pow={1.0,0.0}; unsigned long int u;
if(n != 0) {
if(n < 0) n = -n, x._Val[0] = 1/x._Val[0], x._Val[1] =1/x._Val[1];
for(u = n; ; ) {
if(u & 01) pow._Val[0] *= x._Val[0], pow._Val[1] *= x._Val[1];
if(u >>= 1) x._Val[0] *= x._Val[0], x._Val[1] *= x._Val[1];
else break;
}
}
_Dcomplex p = {pow._Val[0], pow._Val[1]};
return p;
}
#else
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;
}
#endif
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;
#ifdef _MSC_VER
_Fcomplex zdotc = {0.0, 0.0};
if (incx == 1 && incy == 1) {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += conjf(Cf(&x[i]))._Val[0] * Cf(&y[i])._Val[0];
zdotc._Val[1] += conjf(Cf(&x[i]))._Val[1] * Cf(&y[i])._Val[1];
}
} else {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += conjf(Cf(&x[i*incx]))._Val[0] * Cf(&y[i*incy])._Val[0];
zdotc._Val[1] += conjf(Cf(&x[i*incx]))._Val[1] * Cf(&y[i*incy])._Val[1];
}
}
pCf(z) = zdotc;
}
#else
_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;
}
#endif
static inline void zdotc_(doublecomplex *z, integer *n_, doublecomplex *x, integer *incx_, doublecomplex *y, integer *incy_) {
integer n = *n_, incx = *incx_, incy = *incy_, i;
#ifdef _MSC_VER
_Dcomplex zdotc = {0.0, 0.0};
if (incx == 1 && incy == 1) {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += conj(Cd(&x[i]))._Val[0] * Cd(&y[i])._Val[0];
zdotc._Val[1] += conj(Cd(&x[i]))._Val[1] * Cd(&y[i])._Val[1];
}
} else {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += conj(Cd(&x[i*incx]))._Val[0] * Cd(&y[i*incy])._Val[0];
zdotc._Val[1] += conj(Cd(&x[i*incx]))._Val[1] * Cd(&y[i*incy])._Val[1];
}
}
pCd(z) = zdotc;
}
#else
_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;
}
#endif
static inline void cdotu_(complex *z, integer *n_, complex *x, integer *incx_, complex *y, integer *incy_) {
integer n = *n_, incx = *incx_, incy = *incy_, i;
#ifdef _MSC_VER
_Fcomplex zdotc = {0.0, 0.0};
if (incx == 1 && incy == 1) {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += Cf(&x[i])._Val[0] * Cf(&y[i])._Val[0];
zdotc._Val[1] += Cf(&x[i])._Val[1] * Cf(&y[i])._Val[1];
}
} else {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += Cf(&x[i*incx])._Val[0] * Cf(&y[i*incy])._Val[0];
zdotc._Val[1] += Cf(&x[i*incx])._Val[1] * Cf(&y[i*incy])._Val[1];
}
}
pCf(z) = zdotc;
}
#else
_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;
}
#endif
static inline void zdotu_(doublecomplex *z, integer *n_, doublecomplex *x, integer *incx_, doublecomplex *y, integer *incy_) {
integer n = *n_, incx = *incx_, incy = *incy_, i;
#ifdef _MSC_VER
_Dcomplex zdotc = {0.0, 0.0};
if (incx == 1 && incy == 1) {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += Cd(&x[i])._Val[0] * Cd(&y[i])._Val[0];
zdotc._Val[1] += Cd(&x[i])._Val[1] * Cd(&y[i])._Val[1];
}
} else {
for (i=0;i<n;i++) { /* zdotc = zdotc + dconjg(x(i))* y(i) */
zdotc._Val[0] += Cd(&x[i*incx])._Val[0] * Cd(&y[i*incy])._Val[0];
zdotc._Val[1] += Cd(&x[i*incx])._Val[1] * Cd(&y[i*incy])._Val[1];
}
}
pCd(z) = zdotc;
}
#else
_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)
*/
/* > \brief \b SLAG2 computes the eigenvalues of a 2-by-2 generalized eigenvalue problem, with scaling as nece
ssary to avoid over-/underflow. */
/* =========== DOCUMENTATION =========== */
/* Online html documentation available at */
/* http://www.netlib.org/lapack/explore-html/ */
/* > \htmlonly */
/* > Download SLAG2 + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slag2.f
"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slag2.f
"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slag2.f
"> */
/* > [TXT]</a> */
/* > \endhtmlonly */
/* Definition: */
/* =========== */
/* SUBROUTINE SLAG2( A, LDA, B, LDB, SAFMIN, SCALE1, SCALE2, WR1, */
/* WR2, WI ) */
/* INTEGER LDA, LDB */
/* REAL SAFMIN, SCALE1, SCALE2, WI, WR1, WR2 */
/* REAL A( LDA, * ), B( LDB, * ) */
/* > \par Purpose: */
/* ============= */
/* > */
/* > \verbatim */
/* > */
/* > SLAG2 computes the eigenvalues of a 2 x 2 generalized eigenvalue */
/* > problem A - w B, with scaling as necessary to avoid over-/underflow. */
/* > */
/* > The scaling factor "s" results in a modified eigenvalue equation */
/* > */
/* > s A - w B */
/* > */
/* > where s is a non-negative scaling factor chosen so that w, w B, */
/* > and s A do not overflow and, if possible, do not underflow, either. */
/* > \endverbatim */
/* Arguments: */
/* ========== */
/* > \param[in] A */
/* > \verbatim */
/* > A is REAL array, dimension (LDA, 2) */
/* > On entry, the 2 x 2 matrix A. It is assumed that its 1-norm */
/* > is less than 1/SAFMIN. Entries less than */
/* > sqrt(SAFMIN)*norm(A) are subject to being treated as zero. */
/* > \endverbatim */
/* > */
/* > \param[in] LDA */
/* > \verbatim */
/* > LDA is INTEGER */
/* > The leading dimension of the array A. LDA >= 2. */
/* > \endverbatim */
/* > */
/* > \param[in] B */
/* > \verbatim */
/* > B is REAL array, dimension (LDB, 2) */
/* > On entry, the 2 x 2 upper triangular matrix B. It is */
/* > assumed that the one-norm of B is less than 1/SAFMIN. The */
/* > diagonals should be at least sqrt(SAFMIN) times the largest */
/* > element of B (in absolute value); if a diagonal is smaller */
/* > than that, then +/- sqrt(SAFMIN) will be used instead of */
/* > that diagonal. */
/* > \endverbatim */
/* > */
/* > \param[in] LDB */
/* > \verbatim */
/* > LDB is INTEGER */
/* > The leading dimension of the array B. LDB >= 2. */
/* > \endverbatim */
/* > */
/* > \param[in] SAFMIN */
/* > \verbatim */
/* > SAFMIN is REAL */
/* > The smallest positive number s.t. 1/SAFMIN does not */
/* > overflow. (This should always be SLAMCH('S') -- it is an */
/* > argument in order to avoid having to call SLAMCH frequently.) */
/* > \endverbatim */
/* > */
/* > \param[out] SCALE1 */
/* > \verbatim */
/* > SCALE1 is REAL */
/* > A scaling factor used to avoid over-/underflow in the */
/* > eigenvalue equation which defines the first eigenvalue. If */
/* > the eigenvalues are complex, then the eigenvalues are */
/* > ( WR1 +/- WI i ) / SCALE1 (which may lie outside the */
/* > exponent range of the machine), SCALE1=SCALE2, and SCALE1 */
/* > will always be positive. If the eigenvalues are real, then */
/* > the first (real) eigenvalue is WR1 / SCALE1 , but this may */
/* > overflow or underflow, and in fact, SCALE1 may be zero or */
/* > less than the underflow threshold if the exact eigenvalue */
/* > is sufficiently large. */
/* > \endverbatim */
/* > */
/* > \param[out] SCALE2 */
/* > \verbatim */
/* > SCALE2 is REAL */
/* > A scaling factor used to avoid over-/underflow in the */
/* > eigenvalue equation which defines the second eigenvalue. If */
/* > the eigenvalues are complex, then SCALE2=SCALE1. If the */
/* > eigenvalues are real, then the second (real) eigenvalue is */
/* > WR2 / SCALE2 , but this may overflow or underflow, and in */
/* > fact, SCALE2 may be zero or less than the underflow */
/* > threshold if the exact eigenvalue is sufficiently large. */
/* > \endverbatim */
/* > */
/* > \param[out] WR1 */
/* > \verbatim */
/* > WR1 is REAL */
/* > If the eigenvalue is real, then WR1 is SCALE1 times the */
/* > eigenvalue closest to the (2,2) element of A B**(-1). If the */
/* > eigenvalue is complex, then WR1=WR2 is SCALE1 times the real */
/* > part of the eigenvalues. */
/* > \endverbatim */
/* > */
/* > \param[out] WR2 */
/* > \verbatim */
/* > WR2 is REAL */
/* > If the eigenvalue is real, then WR2 is SCALE2 times the */
/* > other eigenvalue. If the eigenvalue is complex, then */
/* > WR1=WR2 is SCALE1 times the real part of the eigenvalues. */
/* > \endverbatim */
/* > */
/* > \param[out] WI */
/* > \verbatim */
/* > WI is REAL */
/* > If the eigenvalue is real, then WI is zero. If the */
/* > eigenvalue is complex, then WI is SCALE1 times the imaginary */
/* > part of the eigenvalues. WI will always be non-negative. */
/* > \endverbatim */
/* Authors: */
/* ======== */
/* > \author Univ. of Tennessee */
/* > \author Univ. of California Berkeley */
/* > \author Univ. of Colorado Denver */
/* > \author NAG Ltd. */
/* > \date June 2016 */
/* > \ingroup realOTHERauxiliary */
/* ===================================================================== */
/* Subroutine */ void slag2_(real *a, integer *lda, real *b, integer *ldb,
real *safmin, real *scale1, real *scale2, real *wr1, real *wr2, real *
wi)
{
/* System generated locals */
integer a_dim1, a_offset, b_dim1, b_offset;
real r__1, r__2, r__3, r__4, r__5, r__6;
/* Local variables */
real diff, bmin, wbig, wabs, wdet, r__, binv11, binv22, discr, anorm,
bnorm, bsize, shift, c1, c2, c3, c4, c5, rtmin, rtmax, wsize, s1,
s2, a11, a12, a21, a22, b11, b12, b22, ascale, bscale, pp, qq, ss,
wscale, safmax, wsmall, as11, as12, as22, sum, abi22;
/* -- 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 */
a_dim1 = *lda;
a_offset = 1 + a_dim1 * 1;
a -= a_offset;
b_dim1 = *ldb;
b_offset = 1 + b_dim1 * 1;
b -= b_offset;
/* Function Body */
rtmin = sqrt(*safmin);
rtmax = 1.f / rtmin;
safmax = 1.f / *safmin;
/* Scale A */
/* Computing MAX */
r__5 = (r__1 = a[a_dim1 + 1], abs(r__1)) + (r__2 = a[a_dim1 + 2], abs(
r__2)), r__6 = (r__3 = a[(a_dim1 << 1) + 1], abs(r__3)) + (r__4 =
a[(a_dim1 << 1) + 2], abs(r__4)), r__5 = f2cmax(r__5,r__6);
anorm = f2cmax(r__5,*safmin);
ascale = 1.f / anorm;
a11 = ascale * a[a_dim1 + 1];
a21 = ascale * a[a_dim1 + 2];
a12 = ascale * a[(a_dim1 << 1) + 1];
a22 = ascale * a[(a_dim1 << 1) + 2];
/* Perturb B if necessary to insure non-singularity */
b11 = b[b_dim1 + 1];
b12 = b[(b_dim1 << 1) + 1];
b22 = b[(b_dim1 << 1) + 2];
/* Computing MAX */
r__1 = abs(b11), r__2 = abs(b12), r__1 = f2cmax(r__1,r__2), r__2 = abs(b22),
r__1 = f2cmax(r__1,r__2);
bmin = rtmin * f2cmax(r__1,rtmin);
if (abs(b11) < bmin) {
b11 = r_sign(&bmin, &b11);
}
if (abs(b22) < bmin) {
b22 = r_sign(&bmin, &b22);
}
/* Scale B */
/* Computing MAX */
r__1 = abs(b11), r__2 = abs(b12) + abs(b22), r__1 = f2cmax(r__1,r__2);
bnorm = f2cmax(r__1,*safmin);
/* Computing MAX */
r__1 = abs(b11), r__2 = abs(b22);
bsize = f2cmax(r__1,r__2);
bscale = 1.f / bsize;
b11 *= bscale;
b12 *= bscale;
b22 *= bscale;
/* Compute larger eigenvalue by method described by C. van Loan */
/* ( AS is A shifted by -SHIFT*B ) */
binv11 = 1.f / b11;
binv22 = 1.f / b22;
s1 = a11 * binv11;
s2 = a22 * binv22;
if (abs(s1) <= abs(s2)) {
as12 = a12 - s1 * b12;
as22 = a22 - s1 * b22;
ss = a21 * (binv11 * binv22);
abi22 = as22 * binv22 - ss * b12;
pp = abi22 * .5f;
shift = s1;
} else {
as12 = a12 - s2 * b12;
as11 = a11 - s2 * b11;
ss = a21 * (binv11 * binv22);
abi22 = -ss * b12;
pp = (as11 * binv11 + abi22) * .5f;
shift = s2;
}
qq = ss * as12;
if ((r__1 = pp * rtmin, abs(r__1)) >= 1.f) {
/* Computing 2nd power */
r__1 = rtmin * pp;
discr = r__1 * r__1 + qq * *safmin;
r__ = sqrt((abs(discr))) * rtmax;
} else {
/* Computing 2nd power */
r__1 = pp;
if (r__1 * r__1 + abs(qq) <= *safmin) {
/* Computing 2nd power */
r__1 = rtmax * pp;
discr = r__1 * r__1 + qq * safmax;
r__ = sqrt((abs(discr))) * rtmin;
} else {
/* Computing 2nd power */
r__1 = pp;
discr = r__1 * r__1 + qq;
r__ = sqrt((abs(discr)));
}
}
/* Note: the test of R in the following IF is to cover the case when */
/* DISCR is small and negative and is flushed to zero during */
/* the calculation of R. On machines which have a consistent */
/* flush-to-zero threshold and handle numbers above that */
/* threshold correctly, it would not be necessary. */
if (discr >= 0.f || r__ == 0.f) {
sum = pp + r_sign(&r__, &pp);
diff = pp - r_sign(&r__, &pp);
wbig = shift + sum;
/* Compute smaller eigenvalue */
wsmall = shift + diff;
/* Computing MAX */
r__1 = abs(wsmall);
if (abs(wbig) * .5f > f2cmax(r__1,*safmin)) {
wdet = (a11 * a22 - a12 * a21) * (binv11 * binv22);
wsmall = wdet / wbig;
}
/* Choose (real) eigenvalue closest to 2,2 element of A*B**(-1) */
/* for WR1. */
if (pp > abi22) {
*wr1 = f2cmin(wbig,wsmall);
*wr2 = f2cmax(wbig,wsmall);
} else {
*wr1 = f2cmax(wbig,wsmall);
*wr2 = f2cmin(wbig,wsmall);
}
*wi = 0.f;
} else {
/* Complex eigenvalues */
*wr1 = shift + pp;
*wr2 = *wr1;
*wi = r__;
}
/* Further scaling to avoid underflow and overflow in computing */
/* SCALE1 and overflow in computing w*B. */
/* This scale factor (WSCALE) is bounded from above using C1 and C2, */
/* and from below using C3 and C4. */
/* C1 implements the condition s A must never overflow. */
/* C2 implements the condition w B must never overflow. */
/* C3, with C2, */
/* implement the condition that s A - w B must never overflow. */
/* C4 implements the condition s should not underflow. */
/* C5 implements the condition f2cmax(s,|w|) should be at least 2. */
c1 = bsize * (*safmin * f2cmax(1.f,ascale));
c2 = *safmin * f2cmax(1.f,bnorm);
c3 = bsize * *safmin;
if (ascale <= 1.f && bsize <= 1.f) {
/* Computing MIN */
r__1 = 1.f, r__2 = ascale / *safmin * bsize;
c4 = f2cmin(r__1,r__2);
} else {
c4 = 1.f;
}
if (ascale <= 1.f || bsize <= 1.f) {
/* Computing MIN */
r__1 = 1.f, r__2 = ascale * bsize;
c5 = f2cmin(r__1,r__2);
} else {
c5 = 1.f;
}
/* Scale first eigenvalue */
wabs = abs(*wr1) + abs(*wi);
/* Computing MAX */
/* Computing MIN */
r__3 = c4, r__4 = f2cmax(wabs,c5) * .5f;
r__1 = f2cmax(*safmin,c1), r__2 = (wabs * c2 + c3) * 1.0000100000000001f,
r__1 = f2cmax(r__1,r__2), r__2 = f2cmin(r__3,r__4);
wsize = f2cmax(r__1,r__2);
if (wsize != 1.f) {
wscale = 1.f / wsize;
if (wsize > 1.f) {
*scale1 = f2cmax(ascale,bsize) * wscale * f2cmin(ascale,bsize);
} else {
*scale1 = f2cmin(ascale,bsize) * wscale * f2cmax(ascale,bsize);
}
*wr1 *= wscale;
if (*wi != 0.f) {
*wi *= wscale;
*wr2 = *wr1;
*scale2 = *scale1;
}
} else {
*scale1 = ascale * bsize;
*scale2 = *scale1;
}
/* Scale second eigenvalue (if real) */
if (*wi == 0.f) {
/* Computing MAX */
/* Computing MIN */
/* Computing MAX */
r__5 = abs(*wr2);
r__3 = c4, r__4 = f2cmax(r__5,c5) * .5f;
r__1 = f2cmax(*safmin,c1), r__2 = (abs(*wr2) * c2 + c3) *
1.0000100000000001f, r__1 = f2cmax(r__1,r__2), r__2 = f2cmin(r__3,
r__4);
wsize = f2cmax(r__1,r__2);
if (wsize != 1.f) {
wscale = 1.f / wsize;
if (wsize > 1.f) {
*scale2 = f2cmax(ascale,bsize) * wscale * f2cmin(ascale,bsize);
} else {
*scale2 = f2cmin(ascale,bsize) * wscale * f2cmax(ascale,bsize);
}
*wr2 *= wscale;
} else {
*scale2 = ascale * bsize;
}
}
/* End of SLAG2 */
return;
} /* slag2_ */