1 2 /* @(#)e_sinh.c 1.3 95/01/18 */ 3 /* 4 * ==================================================== 5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6 * 7 * Developed at SunSoft, a Sun Microsystems, Inc. business. 8 * Permission to use, copy, modify, and distribute this 9 * software is freely granted, provided that this notice 10 * is preserved. 11 * ==================================================== 12 */ 13 14 #include <sys/cdefs.h> 15 16 17 /* __ieee754_sinh(x) 18 * Method : 19 * mathematically sinh(x) if defined to be (exp(x)-exp(-x))/2 20 * 1. Replace x by |x| (sinh(-x) = -sinh(x)). 21 * 2. 22 * E + E/(E+1) 23 * 0 <= x <= 22 : sinh(x) := --------------, E=expm1(x) 24 * 2 25 * 26 * 22 <= x <= lnovft : sinh(x) := exp(x)/2 27 * lnovft <= x <= ln2ovft: sinh(x) := exp(x/2)/2 * exp(x/2) 28 * ln2ovft < x : sinh(x) := x*shuge (overflow) 29 * 30 * Special cases: 31 * sinh(x) is |x| if x is +INF, -INF, or NaN. 32 * only sinh(0)=0 is exact for finite x. 33 */ 34 35 #include "openlibm.h" 36 #include "math_private.h" 37 38 static const double one = 1.0, shuge = 1.0e307; 39 40 double 41 __ieee754_sinh(double x) 42 { 43 double t,w,h; 44 int32_t ix,jx; 45 u_int32_t lx; 46 47 /* High word of |x|. */ 48 GET_HIGH_WORD(jx,x); 49 ix = jx&0x7fffffff; 50 51 /* x is INF or NaN */ 52 if(ix>=0x7ff00000) return x+x; 53 54 h = 0.5; 55 if (jx<0) h = -h; 56 /* |x| in [0,22], return sign(x)*0.5*(E+E/(E+1))) */ 57 if (ix < 0x40360000) { /* |x|<22 */ 58 if (ix<0x3e300000) /* |x|<2**-28 */ 59 if(shuge+x>one) return x;/* sinh(tiny) = tiny with inexact */ 60 t = expm1(fabs(x)); 61 if(ix<0x3ff00000) return h*(2.0*t-t*t/(t+one)); 62 return h*(t+t/(t+one)); 63 } 64 65 /* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */ 66 if (ix < 0x40862E42) return h*__ieee754_exp(fabs(x)); 67 68 /* |x| in [log(maxdouble), overflowthresold] */ 69 GET_LOW_WORD(lx,x); 70 if (ix<0x408633CE || ((ix==0x408633ce)&&(lx<=(u_int32_t)0x8fb9f87d))) { 71 w = __ieee754_exp(0.5*fabs(x)); 72 t = h*w; 73 return t*w; 74 } 75 76 /* |x| > overflowthresold, sinh(x) overflow */ 77 return x*shuge; 78 } 79