From 39c808eb0b4e61bcd0e6c9803a13b78da9046b11 Mon Sep 17 00:00:00 2001 From: "William F. Jolitz" Date: Fri, 12 Apr 1991 13:03:53 -0800 Subject: [PATCH 1/1] 386BSD 0.0 development Work on file usr/src/lib/libm/ieee/support.c Work on file usr/src/lib/libm/ieee/cbrt.c Work on file usr/src/lib/libm/ieee/cabs.c Co-Authored-By: Lynne Greer Jolitz Synthesized-from: 386BSD-0.0/src --- usr/src/lib/libm/ieee/cabs.c | 228 ++++++++++++++ usr/src/lib/libm/ieee/cbrt.c | 120 ++++++++ usr/src/lib/libm/ieee/support.c | 524 ++++++++++++++++++++++++++++++++ 3 files changed, 872 insertions(+) create mode 100644 usr/src/lib/libm/ieee/cabs.c create mode 100644 usr/src/lib/libm/ieee/cbrt.c create mode 100644 usr/src/lib/libm/ieee/support.c diff --git a/usr/src/lib/libm/ieee/cabs.c b/usr/src/lib/libm/ieee/cabs.c new file mode 100644 index 0000000000..f40a7e79b1 --- /dev/null +++ b/usr/src/lib/libm/ieee/cabs.c @@ -0,0 +1,228 @@ +/* + * Copyright (c) 1985 Regents of the University of California. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)cabs.c 5.6 (Berkeley) 10/9/90"; +#endif /* not lint */ + +/* HYPOT(X,Y) + * RETURN THE SQUARE ROOT OF X^2 + Y^2 WHERE Z=X+iY + * DOUBLE PRECISION (VAX D format 56 bits, IEEE DOUBLE 53 BITS) + * CODED IN C BY K.C. NG, 11/28/84; + * REVISED BY K.C. NG, 7/12/85. + * + * Required system supported functions : + * copysign(x,y) + * finite(x) + * scalb(x,N) + * sqrt(x) + * + * Method : + * 1. replace x by |x| and y by |y|, and swap x and + * y if y > x (hence x is never smaller than y). + * 2. Hypot(x,y) is computed by: + * Case I, x/y > 2 + * + * y + * hypot = x + ----------------------------- + * 2 + * sqrt ( 1 + [x/y] ) + x/y + * + * Case II, x/y <= 2 + * y + * hypot = x + -------------------------------------------------- + * 2 + * [x/y] - 2 + * (sqrt(2)+1) + (x-y)/y + ----------------------------- + * 2 + * sqrt ( 1 + [x/y] ) + sqrt(2) + * + * + * + * Special cases: + * hypot(x,y) is INF if x or y is +INF or -INF; else + * hypot(x,y) is NAN if x or y is NAN. + * + * Accuracy: + * hypot(x,y) returns the sqrt(x^2+y^2) with error less than 1 ulps (units + * in the last place). See Kahan's "Interval Arithmetic Options in the + * Proposed IEEE Floating Point Arithmetic Standard", Interval Mathematics + * 1980, Edited by Karl L.E. Nickel, pp 99-128. (A faster but less accurate + * code follows in comments.) In a test run with 500,000 random arguments + * on a VAX, the maximum observed error was .959 ulps. + * + * Constants: + * The hexadecimal values are the intended ones for the following constants. + * The decimal values may be used, provided that the compiler will convert + * from decimal to binary accurately enough to produce the hexadecimal values + * shown. + */ +#include "mathimpl.h" + +vc(r2p1hi, 2.4142135623730950345E0 ,8279,411a,ef32,99fc, 2, .9A827999FCEF32) +vc(r2p1lo, 1.4349369327986523769E-17 ,597d,2484,754b,89b3, -55, .84597D89B3754B) +vc(sqrt2, 1.4142135623730950622E0 ,04f3,40b5,de65,33f9, 1, .B504F333F9DE65) + +ic(r2p1hi, 2.4142135623730949234E0 , 1, 1.3504F333F9DE6) +ic(r2p1lo, 1.2537167179050217666E-16 , -53, 1.21165F626CDD5) +ic(sqrt2, 1.4142135623730951455E0 , 0, 1.6A09E667F3BCD) + +#ifdef vccast +#define r2p1hi vccast(r2p1hi) +#define r2p1lo vccast(r2p1lo) +#define sqrt2 vccast(sqrt2) +#endif + +double +hypot(x,y) +double x, y; +{ + static const double zero=0, one=1, + small=1.0E-18; /* fl(1+small)==1 */ + static const ibig=30; /* fl(1+2**(2*ibig))==1 */ + double t,r; + int exp; + + if(finite(x)) + if(finite(y)) + { + x=copysign(x,one); + y=copysign(y,one); + if(y > x) + { t=x; x=y; y=t; } + if(x == zero) return(zero); + if(y == zero) return(x); + exp= logb(x); + if(exp-(int)logb(y) > ibig ) + /* raise inexact flag and return |x| */ + { one+small; return(x); } + + /* start computing sqrt(x^2 + y^2) */ + r=x-y; + if(r>y) { /* x/y > 2 */ + r=x/y; + r=r+sqrt(one+r*r); } + else { /* 1 <= x/y <= 2 */ + r/=y; t=r*(r+2.0); + r+=t/(sqrt2+sqrt(2.0+t)); + r+=r2p1lo; r+=r2p1hi; } + + r=y/r; + return(x+r); + + } + + else if(y==y) /* y is +-INF */ + return(copysign(y,one)); + else + return(y); /* y is NaN and x is finite */ + + else if(x==x) /* x is +-INF */ + return (copysign(x,one)); + else if(finite(y)) + return(x); /* x is NaN, y is finite */ +#if !defined(vax)&&!defined(tahoe) + else if(y!=y) return(y); /* x and y is NaN */ +#endif /* !defined(vax)&&!defined(tahoe) */ + else return(copysign(y,one)); /* y is INF */ +} + +/* CABS(Z) + * RETURN THE ABSOLUTE VALUE OF THE COMPLEX NUMBER Z = X + iY + * DOUBLE PRECISION (VAX D format 56 bits, IEEE DOUBLE 53 BITS) + * CODED IN C BY K.C. NG, 11/28/84. + * REVISED BY K.C. NG, 7/12/85. + * + * Required kernel function : + * hypot(x,y) + * + * Method : + * cabs(z) = hypot(x,y) . + */ + +double +cabs(z) +struct { double x, y;} z; +{ + return hypot(z.x,z.y); +} + +double +z_abs(z) +struct { double x,y;} *z; +{ + return hypot(z->x,z->y); +} + +/* A faster but less accurate version of cabs(x,y) */ +#if 0 +double hypot(x,y) +double x, y; +{ + static const double zero=0, one=1; + small=1.0E-18; /* fl(1+small)==1 */ + static const ibig=30; /* fl(1+2**(2*ibig))==1 */ + double temp; + int exp; + + if(finite(x)) + if(finite(y)) + { + x=copysign(x,one); + y=copysign(y,one); + if(y > x) + { temp=x; x=y; y=temp; } + if(x == zero) return(zero); + if(y == zero) return(x); + exp= logb(x); + x=scalb(x,-exp); + if(exp-(int)logb(y) > ibig ) + /* raise inexact flag and return |x| */ + { one+small; return(scalb(x,exp)); } + else y=scalb(y,-exp); + return(scalb(sqrt(x*x+y*y),exp)); + } + + else if(y==y) /* y is +-INF */ + return(copysign(y,one)); + else + return(y); /* y is NaN and x is finite */ + + else if(x==x) /* x is +-INF */ + return (copysign(x,one)); + else if(finite(y)) + return(x); /* x is NaN, y is finite */ + else if(y!=y) return(y); /* x and y is NaN */ + else return(copysign(y,one)); /* y is INF */ +} +#endif diff --git a/usr/src/lib/libm/ieee/cbrt.c b/usr/src/lib/libm/ieee/cbrt.c new file mode 100644 index 0000000000..cdaf33a935 --- /dev/null +++ b/usr/src/lib/libm/ieee/cbrt.c @@ -0,0 +1,120 @@ +/* + * Copyright (c) 1985 Regents of the University of California. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)cbrt.c 5.9 (Berkeley) 2/13/91"; +#endif /* not lint */ + +#include + +/* kahan's cube root (53 bits IEEE double precision) + * for IEEE machines only + * coded in C by K.C. Ng, 4/30/85 + * + * Accuracy: + * better than 0.667 ulps according to an error analysis. Maximum + * error observed was 0.666 ulps in an 1,000,000 random arguments test. + * + * Warning: this code is semi machine dependent; the ordering of words in + * a floating point number must be known in advance. I assume that the + * long interger at the address of a floating point number will be the + * leading 32 bits of that floating point number (i.e., sign, exponent, + * and the 20 most significant bits). + * On a National machine, it has different ordering; therefore, this code + * must be compiled with flag -DNATIONAL. + */ +#if !defined(vax)&&!defined(tahoe) + +static const unsigned long + B1 = 715094163, /* B1 = (682-0.03306235651)*2**20 */ + B2 = 696219795; /* B2 = (664-0.03306235651)*2**20 */ +static const double + C= 19./35., + D= -864./1225., + E= 99./70., + F= 45./28., + G= 5./14.; + +double cbrt(x) +double x; +{ + double r,s,t=0.0,w; + unsigned long *px = (unsigned long *) &x, + *pt = (unsigned long *) &t, + mexp,sign; + +#ifdef national /* ordering of words in a floating points number */ + const int n0=1,n1=0; +#else /* national */ + const int n0=0,n1=1; +#endif /* national */ + + mexp=px[n0]&0x7ff00000; + if(mexp==0x7ff00000) return(x); /* cbrt(NaN,INF) is itself */ + if(x==0.0) return(x); /* cbrt(0) is itself */ + + sign=px[n0]&0x80000000; /* sign= sign(x) */ + px[n0] ^= sign; /* x=|x| */ + + + /* rough cbrt to 5 bits */ + if(mexp==0) /* subnormal number */ + {pt[n0]=0x43500000; /* set t= 2**54 */ + t*=x; pt[n0]=pt[n0]/3+B2; + } + else + pt[n0]=px[n0]/3+B1; + + + /* new cbrt to 23 bits, may be implemented in single precision */ + r=t*t/x; + s=C+r*t; + t*=G+F/(s+E+D/s); + + /* chopped to 20 bits and make it larger than cbrt(x) */ + pt[n1]=0; pt[n0]+=0x00000001; + + + /* one step newton iteration to 53 bits with error less than 0.667 ulps */ + s=t*t; /* t*t is exact */ + r=x/s; + w=t+t; + r=(r-t)/(w+r); /* r-t is exact */ + t=t+t*r; + + + /* retore the sign bit */ + pt[n0] |= sign; + return(t); +} +#endif diff --git a/usr/src/lib/libm/ieee/support.c b/usr/src/lib/libm/ieee/support.c new file mode 100644 index 0000000000..e51f62d9dd --- /dev/null +++ b/usr/src/lib/libm/ieee/support.c @@ -0,0 +1,524 @@ +/* + * Copyright (c) 1985 Regents of the University of California. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)support.c 5.6 (Berkeley) 10/9/90"; +#endif /* not lint */ + +/* + * Some IEEE standard 754 recommended functions and remainder and sqrt for + * supporting the C elementary functions. + ****************************************************************************** + * WARNING: + * These codes are developed (in double) to support the C elementary + * functions temporarily. They are not universal, and some of them are very + * slow (in particular, drem and sqrt is extremely inefficient). Each + * computer system should have its implementation of these functions using + * its own assembler. + ****************************************************************************** + * + * IEEE 754 required operations: + * drem(x,p) + * returns x REM y = x - [x/y]*y , where [x/y] is the integer + * nearest x/y; in half way case, choose the even one. + * sqrt(x) + * returns the square root of x correctly rounded according to + * the rounding mod. + * + * IEEE 754 recommended functions: + * (a) copysign(x,y) + * returns x with the sign of y. + * (b) scalb(x,N) + * returns x * (2**N), for integer values N. + * (c) logb(x) + * returns the unbiased exponent of x, a signed integer in + * double precision, except that logb(0) is -INF, logb(INF) + * is +INF, and logb(NAN) is that NAN. + * (d) finite(x) + * returns the value TRUE if -INF < x < +INF and returns + * FALSE otherwise. + * + * + * CODED IN C BY K.C. NG, 11/25/84; + * REVISED BY K.C. NG on 1/22/85, 2/13/85, 3/24/85. + */ + +#include "mathimpl.h" + +#if defined(vax)||defined(tahoe) /* VAX D format */ +#include + static const unsigned short msign=0x7fff , mexp =0x7f80 ; + static const short prep1=57, gap=7, bias=129 ; + static const double novf=1.7E38, nunf=3.0E-39, zero=0.0 ; +#else /* defined(vax)||defined(tahoe) */ + static const unsigned short msign=0x7fff, mexp =0x7ff0 ; + static const short prep1=54, gap=4, bias=1023 ; + static const double novf=1.7E308, nunf=3.0E-308,zero=0.0; +#endif /* defined(vax)||defined(tahoe) */ + +double scalb(x,N) +double x; int N; +{ + int k; + +#ifdef national + unsigned short *px=(unsigned short *) &x + 3; +#else /* national */ + unsigned short *px=(unsigned short *) &x; +#endif /* national */ + + if( x == zero ) return(x); + +#if defined(vax)||defined(tahoe) + if( (k= *px & mexp ) != ~msign ) { + if (N < -260) + return(nunf*nunf); + else if (N > 260) { + return(copysign(infnan(ERANGE),x)); + } +#else /* defined(vax)||defined(tahoe) */ + if( (k= *px & mexp ) != mexp ) { + if( N<-2100) return(nunf*nunf); else if(N>2100) return(novf+novf); + if( k == 0 ) { + x *= scalb(1.0,(int)prep1); N -= prep1; return(scalb(x,N));} +#endif /* defined(vax)||defined(tahoe) */ + + if((k = (k>>gap)+ N) > 0 ) + if( k < (mexp>>gap) ) *px = (*px&~mexp) | (k< -prep1 ) + /* gradual underflow */ + {*px=(*px&~mexp)|(short)(1<>gap)-bias); +#else /* defined(vax)||defined(tahoe) */ + if( (k= *px & mexp ) != mexp ) + if ( k != 0 ) + return ( (k>>gap) - bias ); + else if( x != zero) + return ( -1022.0 ); + else + return(-(1.0/zero)); + else if(x != x) + return(x); + else + {*px &= msign; return(x);} +#endif /* defined(vax)||defined(tahoe) */ +} + +finite(x) +double x; +{ +#if defined(vax)||defined(tahoe) + return(1); +#else /* defined(vax)||defined(tahoe) */ +#ifdef national + return( (*((short *) &x+3 ) & mexp ) != mexp ); +#else /* national */ + return( (*((short *) &x ) & mexp ) != mexp ); +#endif /* national */ +#endif /* defined(vax)||defined(tahoe) */ +} + +double drem(x,p) +double x,p; +{ + short sign; + double hp,dp,tmp; + unsigned short k; +#ifdef national + unsigned short + *px=(unsigned short *) &x +3, + *pp=(unsigned short *) &p +3, + *pd=(unsigned short *) &dp +3, + *pt=(unsigned short *) &tmp+3; +#else /* national */ + unsigned short + *px=(unsigned short *) &x , + *pp=(unsigned short *) &p , + *pd=(unsigned short *) &dp , + *pt=(unsigned short *) &tmp; +#endif /* national */ + + *pp &= msign ; + +#if defined(vax)||defined(tahoe) + if( ( *px & mexp ) == ~msign ) /* is x a reserved operand? */ +#else /* defined(vax)||defined(tahoe) */ + if( ( *px & mexp ) == mexp ) +#endif /* defined(vax)||defined(tahoe) */ + return (x-p)-(x-p); /* create nan if x is inf */ + if (p == zero) { +#if defined(vax)||defined(tahoe) + return(infnan(EDOM)); +#else /* defined(vax)||defined(tahoe) */ + return zero/zero; +#endif /* defined(vax)||defined(tahoe) */ + } + +#if defined(vax)||defined(tahoe) + if( ( *pp & mexp ) == ~msign ) /* is p a reserved operand? */ +#else /* defined(vax)||defined(tahoe) */ + if( ( *pp & mexp ) == mexp ) +#endif /* defined(vax)||defined(tahoe) */ + { if (p != p) return p; else return x;} + + else if ( ((*pp & mexp)>>gap) <= 1 ) + /* subnormal p, or almost subnormal p */ + { double b; b=scalb(1.0,(int)prep1); + p *= b; x = drem(x,p); x *= b; return(drem(x,p)/b);} + else if ( p >= novf/2) + { p /= 2 ; x /= 2; return(drem(x,p)*2);} + else + { + dp=p+p; hp=p/2; + sign= *px & ~msign ; + *px &= msign ; + while ( x > dp ) + { + k=(*px & mexp) - (*pd & mexp) ; + tmp = dp ; + *pt += k ; + +#if defined(vax)||defined(tahoe) + if( x < tmp ) *pt -= 128 ; +#else /* defined(vax)||defined(tahoe) */ + if( x < tmp ) *pt -= 16 ; +#endif /* defined(vax)||defined(tahoe) */ + + x -= tmp ; + } + if ( x > hp ) + { x -= p ; if ( x >= hp ) x -= p ; } + +#if defined(vax)||defined(tahoe) + if (x) +#endif /* defined(vax)||defined(tahoe) */ + *px ^= sign; + return( x); + + } +} + + +double sqrt(x) +double x; +{ + double q,s,b,r; + double t; + double const zero=0.0; + int m,n,i; +#if defined(vax)||defined(tahoe) + int k=54; +#else /* defined(vax)||defined(tahoe) */ + int k=51; +#endif /* defined(vax)||defined(tahoe) */ + + /* sqrt(NaN) is NaN, sqrt(+-0) = +-0 */ + if(x!=x||x==zero) return(x); + + /* sqrt(negative) is invalid */ + if(x1.0) t=1; /* b>1 : Round-to-(+INF) */ + if(t>=0) q+=r; } /* else: Round-to-nearest */ + else { + s *= 2; x *= 4; + t = (x-s)-1; + b=1.0+3*r/4; if(b==1.0) goto end; + b=1.0+r/4; if(b>1.0) t=1; + if(t>=0) q+=r; } + +end: return(scalb(q,n)); +} + +#if 0 +/* DREM(X,Y) + * RETURN X REM Y =X-N*Y, N=[X/Y] ROUNDED (ROUNDED TO EVEN IN THE HALF WAY CASE) + * DOUBLE PRECISION (VAX D format 56 bits, IEEE DOUBLE 53 BITS) + * INTENDED FOR ASSEMBLY LANGUAGE + * CODED IN C BY K.C. NG, 3/23/85, 4/8/85. + * + * Warning: this code should not get compiled in unless ALL of + * the following machine-dependent routines are supplied. + * + * Required machine dependent functions (not on a VAX): + * swapINX(i): save inexact flag and reset it to "i" + * swapENI(e): save inexact enable and reset it to "e" + */ + +double drem(x,y) +double x,y; +{ + +#ifdef national /* order of words in floating point number */ + static const n0=3,n1=2,n2=1,n3=0; +#else /* VAX, SUN, ZILOG, TAHOE */ + static const n0=0,n1=1,n2=2,n3=3; +#endif + + static const unsigned short mexp =0x7ff0, m25 =0x0190, m57 =0x0390; + static const double zero=0.0; + double hy,y1,t,t1; + short k; + long n; + int i,e; + unsigned short xexp,yexp, *px =(unsigned short *) &x , + nx,nf, *py =(unsigned short *) &y , + sign, *pt =(unsigned short *) &t , + *pt1 =(unsigned short *) &t1 ; + + xexp = px[n0] & mexp ; /* exponent of x */ + yexp = py[n0] & mexp ; /* exponent of y */ + sign = px[n0] &0x8000; /* sign of x */ + +/* return NaN if x is NaN, or y is NaN, or x is INF, or y is zero */ + if(x!=x) return(x); if(y!=y) return(y); /* x or y is NaN */ + if( xexp == mexp ) return(zero/zero); /* x is INF */ + if(y==zero) return(y/y); + +/* save the inexact flag and inexact enable in i and e respectively + * and reset them to zero + */ + i=swapINX(0); e=swapENI(0); + +/* subnormal number */ + nx=0; + if(yexp==0) {t=1.0,pt[n0]+=m57; y*=t; nx=m57;} + +/* if y is tiny (biased exponent <= 57), scale up y to y*2**57 */ + if( yexp <= m57 ) {py[n0]+=m57; nx+=m57; yexp+=m57;} + + nf=nx; + py[n0] &= 0x7fff; + px[n0] &= 0x7fff; + +/* mask off the least significant 27 bits of y */ + t=y; pt[n3]=0; pt[n2]&=0xf800; y1=t; + +/* LOOP: argument reduction on x whenever x > y */ +loop: + while ( x > y ) + { + t=y; + t1=y1; + xexp=px[n0]&mexp; /* exponent of x */ + k=xexp-yexp-m25; + if(k>0) /* if x/y >= 2**26, scale up y so that x/y < 2**26 */ + {pt[n0]+=k;pt1[n0]+=k;} + n=x/t; x=(x-n*t1)-n*(t-t1); + } + /* end while (x > y) */ + + if(nx!=0) {t=1.0; pt[n0]+=nx; x*=t; nx=0; goto loop;} + +/* final adjustment */ + + hy=y/2.0; + if(x>hy||((x==hy)&&n%2==1)) x-=y; + px[n0] ^= sign; + if(nf!=0) { t=1.0; pt[n0]-=nf; x*=t;} + +/* restore inexact flag and inexact enable */ + swapINX(i); swapENI(e); + + return(x); +} +#endif + +#if 0 +/* SQRT + * RETURN CORRECTLY ROUNDED (ACCORDING TO THE ROUNDING MODE) SQRT + * FOR IEEE DOUBLE PRECISION ONLY, INTENDED FOR ASSEMBLY LANGUAGE + * CODED IN C BY K.C. NG, 3/22/85. + * + * Warning: this code should not get compiled in unless ALL of + * the following machine-dependent routines are supplied. + * + * Required machine dependent functions: + * swapINX(i) ...return the status of INEXACT flag and reset it to "i" + * swapRM(r) ...return the current Rounding Mode and reset it to "r" + * swapENI(e) ...return the status of inexact enable and reset it to "e" + * addc(t) ...perform t=t+1 regarding t as a 64 bit unsigned integer + * subc(t) ...perform t=t-1 regarding t as a 64 bit unsigned integer + */ + +static const unsigned long table[] = { +0, 1204, 3062, 5746, 9193, 13348, 18162, 23592, 29598, 36145, 43202, 50740, +58733, 67158, 75992, 85215, 83599, 71378, 60428, 50647, 41945, 34246, 27478, +21581, 16499, 12183, 8588, 5674, 3403, 1742, 661, 130, }; + +double newsqrt(x) +double x; +{ + double y,z,t,addc(),subc() + double const b54=134217728.*134217728.; /* b54=2**54 */ + long mx,scalx; + long const mexp=0x7ff00000; + int i,j,r,e,swapINX(),swapRM(),swapENI(); + unsigned long *py=(unsigned long *) &y , + *pt=(unsigned long *) &t , + *px=(unsigned long *) &x ; +#ifdef national /* ordering of word in a floating point number */ + const int n0=1, n1=0; +#else + const int n0=0, n1=1; +#endif +/* Rounding Mode: RN ...round-to-nearest + * RZ ...round-towards 0 + * RP ...round-towards +INF + * RM ...round-towards -INF + */ + const int RN=0,RZ=1,RP=2,RM=3; + /* machine dependent: work on a Zilog Z8070 + * and a National 32081 & 16081 + */ + +/* exceptions */ + if(x!=x||x==0.0) return(x); /* sqrt(NaN) is NaN, sqrt(+-0) = +-0 */ + if(x<0) return((x-x)/(x-x)); /* sqrt(negative) is invalid */ + if((mx=px[n0]&mexp)==mexp) return(x); /* sqrt(+INF) is +INF */ + +/* save, reset, initialize */ + e=swapENI(0); /* ...save and reset the inexact enable */ + i=swapINX(0); /* ...save INEXACT flag */ + r=swapRM(RN); /* ...save and reset the Rounding Mode to RN */ + scalx=0; + +/* subnormal number, scale up x to x*2**54 */ + if(mx==0) {x *= b54 ; scalx-=0x01b00000;} + +/* scale x to avoid intermediate over/underflow: + * if (x > 2**512) x=x/2**512; if (x < 2**-512) x=x*2**512 */ + if(mx>0x5ff00000) {px[n0] -= 0x20000000; scalx+= 0x10000000;} + if(mx<0x1ff00000) {px[n0] += 0x20000000; scalx-= 0x10000000;} + +/* magic initial approximation to almost 8 sig. bits */ + py[n0]=(px[n0]>>1)+0x1ff80000; + py[n0]=py[n0]-table[(py[n0]>>15)&31]; + +/* Heron's rule once with correction to improve y to almost 18 sig. bits */ + t=x/y; y=y+t; py[n0]=py[n0]-0x00100006; py[n1]=0; + +/* triple to almost 56 sig. bits; now y approx. sqrt(x) to within 1 ulp */ + t=y*y; z=t; pt[n0]+=0x00100000; t+=z; z=(x-z)*y; + t=z/(t+x) ; pt[n0]+=0x00100000; y+=t; + +/* twiddle last bit to force y correctly rounded */ + swapRM(RZ); /* ...set Rounding Mode to round-toward-zero */ + swapINX(0); /* ...clear INEXACT flag */ + swapENI(e); /* ...restore inexact enable status */ + t=x/y; /* ...chopped quotient, possibly inexact */ + j=swapINX(i); /* ...read and restore inexact flag */ + if(j==0) { if(t==y) goto end; else t=subc(t); } /* ...t=t-ulp */ + b54+0.1; /* ..trigger inexact flag, sqrt(x) is inexact */ + if(r==RN) t=addc(t); /* ...t=t+ulp */ + else if(r==RP) { t=addc(t);y=addc(y);}/* ...t=t+ulp;y=y+ulp; */ + y=y+t; /* ...chopped sum */ + py[n0]=py[n0]-0x00100000; /* ...correctly rounded sqrt(x) */ +end: py[n0]=py[n0]+scalx; /* ...scale back y */ + swapRM(r); /* ...restore Rounding Mode */ + return(y); +} +#endif -- 2.20.1