pip-install-ghxuqwgs/numpy_78e94bf2b6094bf9a1f3d92042f9bf46/numpy/linalg/lapack_lite/dlamch.c

#include <stdio.h>
#include "f2c.h"

/* If config.h is available, we only need dlamc3 */
#ifndef HAVE_CONFIG
doublereal dlamch_(char *cmach)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       October 31, 1992


    Purpose
    =======

    DLAMCH determines double precision machine parameters.

    Arguments
    =========

    CMACH   (input) CHARACTER*1
            Specifies the value to be returned by DLAMCH:
            = 'E' or 'e',   DLAMCH := eps
            = 'S' or 's ,   DLAMCH := sfmin
            = 'B' or 'b',   DLAMCH := base
            = 'P' or 'p',   DLAMCH := eps*base
            = 'N' or 'n',   DLAMCH := t
            = 'R' or 'r',   DLAMCH := rnd
            = 'M' or 'm',   DLAMCH := emin
            = 'U' or 'u',   DLAMCH := rmin
            = 'L' or 'l',   DLAMCH := emax
            = 'O' or 'o',   DLAMCH := rmax

            where

            eps   = relative machine precision
            sfmin = safe minimum, such that 1/sfmin does not overflow
            base  = base of the machine
            prec  = eps*base
            t     = number of (base) digits in the mantissa
            rnd   = 1.0 when rounding occurs in addition, 0.0 otherwise
            emin  = minimum exponent before (gradual) underflow
            rmin  = underflow threshold - base**(emin-1)
            emax  = largest exponent before overflow
            rmax  = overflow threshold  - (base**emax)*(1-eps)

   =====================================================================
*/
/* >>Start of File<<
       Initialized data */
    static logical first = TRUE_;
    /* System generated locals */
    integer i__1;
    doublereal ret_val;
    /* Builtin functions */
    double pow_di(doublereal *, integer *);
    /* Local variables */
    static doublereal base;
    static integer beta;
    static doublereal emin, prec, emax;
    static integer imin, imax;
    static logical lrnd;
    static doublereal rmin, rmax, t, rmach;
    extern logical lsame_(char *, char *);
    static doublereal small, sfmin;
    extern /* Subroutine */ int dlamc2_(integer *, integer *, logical *,
	    doublereal *, integer *, doublereal *, integer *, doublereal *);
    static integer it;
    static doublereal rnd, eps;



    if (first) {
	first = FALSE_;
	dlamc2_(&beta, &it, &lrnd, &eps, &imin, &rmin, &imax, &rmax);
	base = (doublereal) beta;
	t = (doublereal) it;
	if (lrnd) {
	    rnd = 1.;
	    i__1 = 1 - it;
	    eps = pow_di(&base, &i__1) / 2;
	} else {
	    rnd = 0.;
	    i__1 = 1 - it;
	    eps = pow_di(&base, &i__1);
	}
	prec = eps * base;
	emin = (doublereal) imin;
	emax = (doublereal) imax;
	sfmin = rmin;
	small = 1. / rmax;
	if (small >= sfmin) {

/*           Use SMALL plus a bit, to avoid the possibility of rou
nding
             causing overflow when computing  1/sfmin. */

	    sfmin = small * (eps + 1.);
	}
    }

    if (lsame_(cmach, "E")) {
	rmach = eps;
    } else if (lsame_(cmach, "S")) {
	rmach = sfmin;
    } else if (lsame_(cmach, "B")) {
	rmach = base;
    } else if (lsame_(cmach, "P")) {
	rmach = prec;
    } else if (lsame_(cmach, "N")) {
	rmach = t;
    } else if (lsame_(cmach, "R")) {
	rmach = rnd;
    } else if (lsame_(cmach, "M")) {
	rmach = emin;
    } else if (lsame_(cmach, "U")) {
	rmach = rmin;
    } else if (lsame_(cmach, "L")) {
	rmach = emax;
    } else if (lsame_(cmach, "O")) {
	rmach = rmax;
    }

    ret_val = rmach;
    return ret_val;

/*     End of DLAMCH */

} /* dlamch_ */


/* Subroutine */ int dlamc1_(integer *beta, integer *t, logical *rnd, logical
	*ieee1)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       October 31, 1992


    Purpose
    =======

    DLAMC1 determines the machine parameters given by BETA, T, RND, and
    IEEE1.

    Arguments
    =========

    BETA    (output) INTEGER
            The base of the machine.

    T       (output) INTEGER
            The number of ( BETA ) digits in the mantissa.

    RND     (output) LOGICAL
            Specifies whether proper rounding  ( RND = .TRUE. )  or
            chopping  ( RND = .FALSE. )  occurs in addition. This may not

            be a reliable guide to the way in which the machine performs

            its arithmetic.

    IEEE1   (output) LOGICAL
            Specifies whether rounding appears to be done in the IEEE
            'round to nearest' style.

    Further Details
    ===============

    The routine is based on the routine  ENVRON  by Malcolm and
    incorporates suggestions by Gentleman and Marovich. See

       Malcolm M. A. (1972) Algorithms to reveal properties of
          floating-point arithmetic. Comms. of the ACM, 15, 949-951.

       Gentleman W. M. and Marovich S. B. (1974) More on algorithms
          that reveal properties of floating point arithmetic units.
          Comms. of the ACM, 17, 276-277.

   =====================================================================
*/
    /* Initialized data */
    static logical first = TRUE_;
    /* System generated locals */
    doublereal d__1, d__2;
    /* Local variables */
    static logical lrnd;
    static doublereal a, b, c, f;
    static integer lbeta;
    static doublereal savec;
    extern doublereal dlamc3_(doublereal *, doublereal *);
    static logical lieee1;
    static doublereal t1, t2;
    static integer lt;
    static doublereal one, qtr;



    if (first) {
	first = FALSE_;
	one = 1.;

/*        LBETA,  LIEEE1,  LT and  LRND  are the  local values  of  BE
TA,
          IEEE1, T and RND.

          Throughout this routine  we use the function  DLAMC3  to ens
ure
          that relevant values are  stored and not held in registers,
 or
          are not affected by optimizers.

          Compute  a = 2.0**m  with the  smallest positive integer m s
uch
          that

             fl( a + 1.0 ) = a. */

	a = 1.;
	c = 1.;

/* +       WHILE( C.EQ.ONE )LOOP */
L10:
	if (c == one) {
	    a *= 2;
	    c = dlamc3_(&a, &one);
	    d__1 = -a;
	    c = dlamc3_(&c, &d__1);
	    goto L10;
	}
/* +       END WHILE

          Now compute  b = 2.0**m  with the smallest positive integer
m
          such that

             fl( a + b ) .gt. a. */

	b = 1.;
	c = dlamc3_(&a, &b);

/* +       WHILE( C.EQ.A )LOOP */
L20:
	if (c == a) {
	    b *= 2;
	    c = dlamc3_(&a, &b);
	    goto L20;
	}
/* +       END WHILE

          Now compute the base.  a and c  are neighbouring floating po
int
          numbers  in the  interval  ( beta**t, beta**( t + 1 ) )  and
 so
          their difference is beta. Adding 0.25 to c is to ensure that
 it
          is truncated to beta and not ( beta - 1 ). */

	qtr = one / 4;
	savec = c;
	d__1 = -a;
	c = dlamc3_(&c, &d__1);
	lbeta = (integer) (c + qtr);

/*        Now determine whether rounding or chopping occurs,  by addin
g a
          bit  less  than  beta/2  and a  bit  more  than  beta/2  to
 a. */

	b = (doublereal) lbeta;
	d__1 = b / 2;
	d__2 = -b / 100;
	f = dlamc3_(&d__1, &d__2);
	c = dlamc3_(&f, &a);
	if (c == a) {
	    lrnd = TRUE_;
	} else {
	    lrnd = FALSE_;
	}
	d__1 = b / 2;
	d__2 = b / 100;
	f = dlamc3_(&d__1, &d__2);
	c = dlamc3_(&f, &a);
	if (lrnd && c == a) {
	    lrnd = FALSE_;
	}

/*        Try and decide whether rounding is done in the  IEEE  'round
 to
          nearest' style. B/2 is half a unit in the last place of the
two
          numbers A and SAVEC. Furthermore, A is even, i.e. has last
bit
          zero, and SAVEC is odd. Thus adding B/2 to A should not  cha
nge
          A, but adding B/2 to SAVEC should change SAVEC. */

	d__1 = b / 2;
	t1 = dlamc3_(&d__1, &a);
	d__1 = b / 2;
	t2 = dlamc3_(&d__1, &savec);
	lieee1 = t1 == a && t2 > savec && lrnd;

/*        Now find  the  mantissa, t.  It should  be the  integer part
 of
          log to the base beta of a,  however it is safer to determine
  t
          by powering.  So we find t as the smallest positive integer
for
          which

             fl( beta**t + 1.0 ) = 1.0. */

	lt = 0;
	a = 1.;
	c = 1.;

/* +       WHILE( C.EQ.ONE )LOOP */
L30:
	if (c == one) {
	    ++lt;
	    a *= lbeta;
	    c = dlamc3_(&a, &one);
	    d__1 = -a;
	    c = dlamc3_(&c, &d__1);
	    goto L30;
	}
/* +       END WHILE */

    }

    *beta = lbeta;
    *t = lt;
    *rnd = lrnd;
    *ieee1 = lieee1;
    return 0;

/*     End of DLAMC1 */

} /* dlamc1_ */


/* Subroutine */ int dlamc2_(integer *beta, integer *t, logical *rnd,
	doublereal *eps, integer *emin, doublereal *rmin, integer *emax,
	doublereal *rmax)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       October 31, 1992


    Purpose
    =======

    DLAMC2 determines the machine parameters specified in its argument
    list.

    Arguments
    =========

    BETA    (output) INTEGER
            The base of the machine.

    T       (output) INTEGER
            The number of ( BETA ) digits in the mantissa.

    RND     (output) LOGICAL
            Specifies whether proper rounding  ( RND = .TRUE. )  or
            chopping  ( RND = .FALSE. )  occurs in addition. This may not

            be a reliable guide to the way in which the machine performs

            its arithmetic.

    EPS     (output) DOUBLE PRECISION
            The smallest positive number such that

               fl( 1.0 - EPS ) .LT. 1.0,

            where fl denotes the computed value.

    EMIN    (output) INTEGER
            The minimum exponent before (gradual) underflow occurs.

    RMIN    (output) DOUBLE PRECISION
            The smallest normalized number for the machine, given by
            BASE**( EMIN - 1 ), where  BASE  is the floating point value

            of BETA.

    EMAX    (output) INTEGER
            The maximum exponent before overflow occurs.

    RMAX    (output) DOUBLE PRECISION
            The largest positive number for the machine, given by
            BASE**EMAX * ( 1 - EPS ), where  BASE  is the floating point

            value of BETA.

    Further Details
    ===============

    The computation of  EPS  is based on a routine PARANOIA by
    W. Kahan of the University of California at Berkeley.

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

    /* Initialized data */
    static logical first = TRUE_;
    static logical iwarn = FALSE_;
    /* System generated locals */
    integer i__1;
    doublereal d__1, d__2, d__3, d__4, d__5;
    /* Builtin functions */
    double pow_di(doublereal *, integer *);
    /* Local variables */
    static logical ieee;
    static doublereal half;
    static logical lrnd;
    static doublereal leps, zero, a, b, c;
    static integer i, lbeta;
    static doublereal rbase;
    static integer lemin, lemax, gnmin;
    static doublereal small;
    static integer gpmin;
    static doublereal third, lrmin, lrmax, sixth;
    extern /* Subroutine */ int dlamc1_(integer *, integer *, logical *,
	    logical *);
    extern doublereal dlamc3_(doublereal *, doublereal *);
    static logical lieee1;
    extern /* Subroutine */ int dlamc4_(integer *, doublereal *, integer *),
	    dlamc5_(integer *, integer *, integer *, logical *, integer *,
	    doublereal *);
    static integer lt, ngnmin, ngpmin;
    static doublereal one, two;



    if (first) {
	first = FALSE_;
	zero = 0.;
	one = 1.;
	two = 2.;

/*        LBETA, LT, LRND, LEPS, LEMIN and LRMIN  are the local values
 of
          BETA, T, RND, EPS, EMIN and RMIN.

          Throughout this routine  we use the function  DLAMC3  to ens
ure
          that relevant values are stored  and not held in registers,
 or
          are not affected by optimizers.

          DLAMC1 returns the parameters  LBETA, LT, LRND and LIEEE1.
*/

	dlamc1_(&lbeta, &lt, &lrnd, &lieee1);

/*        Start to find EPS. */

	b = (doublereal) lbeta;
	i__1 = -lt;
	a = pow_di(&b, &i__1);
	leps = a;

/*        Try some tricks to see whether or not this is the correct  E
PS. */

	b = two / 3;
	half = one / 2;
	d__1 = -half;
	sixth = dlamc3_(&b, &d__1);
	third = dlamc3_(&sixth, &sixth);
	d__1 = -half;
	b = dlamc3_(&third, &d__1);
	b = dlamc3_(&b, &sixth);
	b = abs(b);
	if (b < leps) {
	    b = leps;
	}

	leps = 1.;

/* +       WHILE( ( LEPS.GT.B ).AND.( B.GT.ZERO ) )LOOP */
L10:
	if (leps > b && b > zero) {
	    leps = b;
	    d__1 = half * leps;
/* Computing 5th power */
	    d__3 = two, d__4 = d__3, d__3 *= d__3;
/* Computing 2nd power */
	    d__5 = leps;
	    d__2 = d__4 * (d__3 * d__3) * (d__5 * d__5);
	    c = dlamc3_(&d__1, &d__2);
	    d__1 = -c;
	    c = dlamc3_(&half, &d__1);
	    b = dlamc3_(&half, &c);
	    d__1 = -b;
	    c = dlamc3_(&half, &d__1);
	    b = dlamc3_(&half, &c);
	    goto L10;
	}
/* +       END WHILE */

	if (a < leps) {
	    leps = a;
	}

/*        Computation of EPS complete.

          Now find  EMIN.  Let A = + or - 1, and + or - (1 + BASE**(-3
)).
          Keep dividing  A by BETA until (gradual) underflow occurs. T
his
          is detected when we cannot recover the previous A. */

	rbase = one / lbeta;
	small = one;
	for (i = 1; i <= 3; ++i) {
	    d__1 = small * rbase;
	    small = dlamc3_(&d__1, &zero);
/* L20: */
	}
	a = dlamc3_(&one, &small);
	dlamc4_(&ngpmin, &one, &lbeta);
	d__1 = -one;
	dlamc4_(&ngnmin, &d__1, &lbeta);
	dlamc4_(&gpmin, &a, &lbeta);
	d__1 = -a;
	dlamc4_(&gnmin, &d__1, &lbeta);
	ieee = FALSE_;

	if (ngpmin == ngnmin && gpmin == gnmin) {
	    if (ngpmin == gpmin) {
		lemin = ngpmin;
/*            ( Non twos-complement machines, no gradual under
flow;
                e.g.,  VAX ) */
	    } else if (gpmin - ngpmin == 3) {
		lemin = ngpmin - 1 + lt;
		ieee = TRUE_;
/*            ( Non twos-complement machines, with gradual und
erflow;
                e.g., IEEE standard followers ) */
	    } else {
		lemin = min(ngpmin,gpmin);
/*            ( A guess; no known machine ) */
		iwarn = TRUE_;
	    }

	} else if (ngpmin == gpmin && ngnmin == gnmin) {
	    if ((i__1 = ngpmin - ngnmin, abs(i__1)) == 1) {
		lemin = max(ngpmin,ngnmin);
/*            ( Twos-complement machines, no gradual underflow
;
                e.g., CYBER 205 ) */
	    } else {
		lemin = min(ngpmin,ngnmin);
/*            ( A guess; no known machine ) */
		iwarn = TRUE_;
	    }

	} else if ((i__1 = ngpmin - ngnmin, abs(i__1)) == 1 && gpmin == gnmin)
		 {
	    if (gpmin - min(ngpmin,ngnmin) == 3) {
		lemin = max(ngpmin,ngnmin) - 1 + lt;
/*            ( Twos-complement machines with gradual underflo
w;
                no known machine ) */
	    } else {
		lemin = min(ngpmin,ngnmin);
/*            ( A guess; no known machine ) */
		iwarn = TRUE_;
	    }

	} else {
/* Computing MIN */
	    i__1 = min(ngpmin,ngnmin), i__1 = min(i__1,gpmin);
	    lemin = min(i__1,gnmin);
/*         ( A guess; no known machine ) */
	    iwarn = TRUE_;
	}
/* **
   Comment out this if block if EMIN is ok */
	if (iwarn) {
	    first = TRUE_;
	    printf("\n\n WARNING. The value EMIN may be incorrect:- ");
	    printf("EMIN = %8i\n",lemin);
	    printf("If, after inspection, the value EMIN looks acceptable");
            printf("please comment out \n the IF block as marked within the");
            printf("code of routine DLAMC2, \n otherwise supply EMIN");
            printf("explicitly.\n");
	}
/* **

          Assume IEEE arithmetic if we found denormalised  numbers abo
ve,
          or if arithmetic seems to round in the  IEEE style,  determi
ned
          in routine DLAMC1. A true IEEE machine should have both  thi
ngs
          true; however, faulty machines may have one or the other. */

	ieee = ieee || lieee1;

/*        Compute  RMIN by successive division by  BETA. We could comp
ute
          RMIN as BASE**( EMIN - 1 ),  but some machines underflow dur
ing
          this computation. */

	lrmin = 1.;
	i__1 = 1 - lemin;
	for (i = 1; i <= 1-lemin; ++i) {
	    d__1 = lrmin * rbase;
	    lrmin = dlamc3_(&d__1, &zero);
/* L30: */
	}

/*        Finally, call DLAMC5 to compute EMAX and RMAX. */

	dlamc5_(&lbeta, &lt, &lemin, &ieee, &lemax, &lrmax);
    }

    *beta = lbeta;
    *t = lt;
    *rnd = lrnd;
    *eps = leps;
    *emin = lemin;
    *rmin = lrmin;
    *emax = lemax;
    *rmax = lrmax;

    return 0;


/*     End of DLAMC2 */

} /* dlamc2_ */
#endif


doublereal dlamc3_(doublereal *a, doublereal *b)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       October 31, 1992


    Purpose
    =======

    DLAMC3  is intended to force  A  and  B  to be stored prior to doing

    the addition of  A  and  B ,  for use in situations where optimizers

    might hold one of these in a register.

    Arguments
    =========

    A, B    (input) DOUBLE PRECISION
            The values A and B.

   =====================================================================
*/
/* >>Start of File<<
       System generated locals */
    volatile doublereal ret_val;



    ret_val = *a + *b;

    return ret_val;

/*     End of DLAMC3 */

} /* dlamc3_ */


#ifndef HAVE_CONFIG
/* Subroutine */ int dlamc4_(integer *emin, doublereal *start, integer *base)
{
/*  -- LAPACK auxiliary routine (version 2.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       October 31, 1992


    Purpose
    =======

    DLAMC4 is a service routine for DLAMC2.

    Arguments
    =========

    EMIN    (output) EMIN
            The minimum exponent before (gradual) underflow, computed by

            setting A = START and dividing by BASE until the previous A
            can not be recovered.

    START   (input) DOUBLE PRECISION
            The starting point for determining EMIN.

    BASE    (input) INTEGER
            The base of the machine.

   =====================================================================
*/
    /* System generated locals */
    integer i__1;
    doublereal d__1;
    /* Local variables */
    static doublereal zero, a;
    static integer i;
    static doublereal rbase, b1, b2, c1, c2, d1, d2;
    extern doublereal dlamc3_(doublereal *, doublereal *);
    static doublereal one;



    a = *start;
    one = 1.;
    rbase = one / *base;
    zero = 0.;
    *emin = 1;
    d__1 = a * rbase;
    b1 = dlamc3_(&d__1, &zero);
    c1 = a;
    c2 = a;
    d1 = a;
    d2 = a;
/* +    WHILE( ( C1.EQ.A ).AND.( C2.EQ.A ).AND.
      $       ( D1.EQ.A ).AND.( D2.EQ.A )      )LOOP */
L10:
    if (c1 == a && c2 == a && d1 == a && d2 == a) {
	--(*emin);
	a = b1;
	d__1 = a / *base;
	b1 = dlamc3_(&d__1, &zero);
	d__1 = b1 * *base;
	c1 = dlamc3_(&d__1, &zero);
	d1 = zero;
	i__1 = *base;
	for (i = 1; i <= *base; ++i) {
	    d1 += b1;
/* L20: */
	}
	d__1 = a * rbase;
	b2 = dlamc3_(&d__1, &zero);
	d__1 = b2 / rbase;
	c2 = dlamc3_(&d__1, &zero);
	d2 = zero;
	i__1 = *base;
	for (i = 1; i <= *base; ++i) {
	    d2 += b2;
/* L30: */
	}
	goto L10;
    }
/* +    END WHILE */

    return 0;

/*     End of DLAMC4 */

} /* dlamc4_ */


/* Subroutine */ int dlamc5_(integer *beta, integer *p, integer *emin,
	logical *ieee, integer *emax, doublereal *rmax)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       October 31, 1992


    Purpose
    =======

    DLAMC5 attempts to compute RMAX, the largest machine floating-point
    number, without overflow.  It assumes that EMAX + abs(EMIN) sum
    approximately to a power of 2.  It will fail on machines where this
    assumption does not hold, for example, the Cyber 205 (EMIN = -28625,

    EMAX = 28718).  It will also fail if the value supplied for EMIN is
    too large (i.e. too close to zero), probably with overflow.

    Arguments
    =========

    BETA    (input) INTEGER
            The base of floating-point arithmetic.

    P       (input) INTEGER
            The number of base BETA digits in the mantissa of a
            floating-point value.

    EMIN    (input) INTEGER
            The minimum exponent before (gradual) underflow.

    IEEE    (input) LOGICAL
            A logical flag specifying whether or not the arithmetic
            system is thought to comply with the IEEE standard.

    EMAX    (output) INTEGER
            The largest exponent before overflow

    RMAX    (output) DOUBLE PRECISION
            The largest machine floating-point number.

   =====================================================================



       First compute LEXP and UEXP, two powers of 2 that bound
       abs(EMIN). We then assume that EMAX + abs(EMIN) will sum
       approximately to the bound that is closest to abs(EMIN).
       (EMAX is the exponent of the required number RMAX). */
    /* Table of constant values */
    static doublereal c_b5 = 0.;

    /* System generated locals */
    integer i__1;
    doublereal d__1;
    /* Local variables */
    static integer lexp;
    static doublereal oldy;
    static integer uexp, i;
    static doublereal y, z;
    static integer nbits;
    extern doublereal dlamc3_(doublereal *, doublereal *);
    static doublereal recbas;
    static integer exbits, expsum, try__;



    lexp = 1;
    exbits = 1;
L10:
    try__ = lexp << 1;
    if (try__ <= -(*emin)) {
	lexp = try__;
	++exbits;
	goto L10;
    }
    if (lexp == -(*emin)) {
	uexp = lexp;
    } else {
	uexp = try__;
	++exbits;
    }

/*     Now -LEXP is less than or equal to EMIN, and -UEXP is greater
       than or equal to EMIN. EXBITS is the number of bits needed to
       store the exponent. */

    if (uexp + *emin > -lexp - *emin) {
	expsum = lexp << 1;
    } else {
	expsum = uexp << 1;
    }

/*     EXPSUM is the exponent range, approximately equal to
       EMAX - EMIN + 1 . */

    *emax = expsum + *emin - 1;
    nbits = exbits + 1 + *p;

/*     NBITS is the total number of bits needed to store a
       floating-point number. */

    if (nbits % 2 == 1 && *beta == 2) {

/*        Either there are an odd number of bits used to store a
          floating-point number, which is unlikely, or some bits are

          not used in the representation of numbers, which is possible
,
          (e.g. Cray machines) or the mantissa has an implicit bit,
          (e.g. IEEE machines, Dec Vax machines), which is perhaps the

          most likely. We have to assume the last alternative.
          If this is true, then we need to reduce EMAX by one because

          there must be some way of representing zero in an implicit-b
it
          system. On machines like Cray, we are reducing EMAX by one

          unnecessarily. */

	--(*emax);
    }

    if (*ieee) {

/*        Assume we are on an IEEE machine which reserves one exponent

          for infinity and NaN. */

	--(*emax);
    }

/*     Now create RMAX, the largest machine number, which should
       be equal to (1.0 - BETA**(-P)) * BETA**EMAX .

       First compute 1.0 - BETA**(-P), being careful that the
       result is less than 1.0 . */

    recbas = 1. / *beta;
    z = *beta - 1.;
    y = 0.;
    i__1 = *p;
    for (i = 1; i <= *p; ++i) {
	z *= recbas;
	if (y < 1.) {
	    oldy = y;
	}
	y = dlamc3_(&y, &z);
/* L20: */
    }
    if (y >= 1.) {
	y = oldy;
    }

/*     Now multiply by BETA**EMAX to get RMAX. */

    i__1 = *emax;
    for (i = 1; i <= *emax; ++i) {
	d__1 = y * *beta;
	y = dlamc3_(&d__1, &c_b5);
/* L30: */
    }

    *rmax = y;
    return 0;

/*     End of DLAMC5 */

} /* dlamc5_ */
#endif