Next on the FDLIBM C -> Java port, expm1.
Coming soon, hyperbolic transcendentals (sinh, cosh, tanh)!
For expm1, the C vs transliteration port show the usual kind of differences,
beside formatting of the constants, the use of the __HI macro on the left-hand
side needs to be replaced by a method call and an assignment, as seen below:
<
< #include "fdlibm.h"
<
< #ifdef __STDC__
< static const double
< #else
< static double
< #endif
< one = 1.0,
< huge = 1.0e+300,
< tiny = 1.0e-300,
< o_threshold = 7.09782712893383973096e+02,/* 0x40862E42, 0xFEFA39EF */
< ln2_hi = 6.93147180369123816490e-01,/* 0x3fe62e42, 0xfee00000 */
< ln2_lo = 1.90821492927058770002e-10,/* 0x3dea39ef, 0x35793c76 */
< invln2 = 1.44269504088896338700e+00,/* 0x3ff71547, 0x652b82fe */
---
> static class Expm1 {
> private static final double one = 1.0;
> private static final double huge = 1.0e+300;
> private static final double tiny = 1.0e-300;
> private static final double o_threshold =
> 7.09782712893383973096e+02; /* 0x40862E42, 0xFEFA39EF */
> private static final double ln2_hi =
> 6.93147180369123816490e-01; /* 0x3fe62e42, 0xfee00000 */
> private static final double ln2_lo =
> 1.90821492927058770002e-10; /* 0x3dea39ef, 0x35793c76 */
> private static final double invln2 =
> 1.44269504088896338700e+00; /* 0x3ff71547, 0x652b82fe */
111,115c104,108
< Q1 = -3.33333333333331316428e-02, /* BFA11111 111110F4 */
< Q2 = 1.58730158725481460165e-03, /* 3F5A01A0 19FE5585 */
< Q3 = -7.93650757867487942473e-05, /* BF14CE19 9EAADBB7 */
< Q4 = 4.00821782732936239552e-06, /* 3ED0CFCA 86E65239 */
< Q5 = -2.01099218183624371326e-07; /* BE8AFDB7 6E09C32D */
---
> private static final double Q1 = -3.33333333333331316428e-02; /*
> BFA11111 111110F4 */
> private static final double Q2 = 1.58730158725481460165e-03; /*
> 3F5A01A0 19FE5585 */
> private static final double Q3 = -7.93650757867487942473e-05; /*
> BF14CE19 9EAADBB7 */
> private static final double Q4 = 4.00821782732936239552e-06; /*
> 3ED0CFCA 86E65239 */
> private static final double Q5 = -2.01099218183624371326e-07; /*
> BE8AFDB7 6E09C32D */
117,123c110
< #ifdef __STDC__
< double expm1(double x)
< #else
< double expm1(x)
< double x;
< #endif
< {
---
> static double compute(double x) {
126c113
< unsigned hx;
---
> /*unsigned*/ int hx;
157c144
< k = invln2*x+((xsb==0)?0.5:-0.5);
---
> k = (int)(invln2*x+((xsb==0)?0.5:-0.5));
188c175
< __HI(y) += (k<<20); /* add k to y's exponent */
---
> y = __HI(y, __HI(y) + (k<<20)); /* add k to y's
> exponent */
193c180
< __HI(t) = 0x3ff00000 - (0x200000>>k); /* t=1-2^-k */
---
> t = __HI(t, 0x3ff00000 - (0x200000>>k)); /* t=1-2^-k */
195c182
< __HI(y) += (k<<20); /* add k to y's exponent */
---
> y = __HI(y, __HI(y) + (k<<20)); /* add k to y's
> exponent */
197c184
< __HI(t) = ((0x3ff-k)<<20); /* 2^-k */
---
> t = __HI(t, ((0x3ff-k)<<20)); /* 2^-k */
200c187
< __HI(y) += (k<<20); /* add k to y's exponent */
---
> y = __HI(y, __HI(y) + (k<<20)); /* add k to y's
> exponent */
205c192
<
---
> }
When comparing the transliteration port and the more idiomatic port, there were
no surprising or notable differences:
$ diff -w Expm1.translit.java Expm1.fdlibm.java
99,102c99,102
< private static final double o_threshold =
7.09782712893383973096e+02; /* 0x40862E42, 0xFEFA39EF */
< private static final double ln2_hi =
6.93147180369123816490e-01; /* 0x3fe62e42, 0xfee00000 */
< private static final double ln2_lo =
1.90821492927058770002e-10; /* 0x3dea39ef, 0x35793c76 */
< private static final double invln2 =
1.44269504088896338700e+00; /* 0x3ff71547, 0x652b82fe */
---
> private static final double o_threshold = 0x1.62e42fefa39efp9; //
> 7.09782712893383973096e+02
> private static final double ln2_hi = 0x1.62e42feep-1; //
> 6.93147180369123816490e-01
> private static final double ln2_lo = 0x1.a39ef35793c76p-33; //
> 1.90821492927058770002e-10
> private static final double invln2 = 0x1.71547652b82fep0; //
> 1.44269504088896338700e+00
104,108c104,108
< private static final double Q1 = -3.33333333333331316428e-02; /*
BFA11111 111110F4 */
< private static final double Q2 = 1.58730158725481460165e-03; /*
3F5A01A0 19FE5585 */
< private static final double Q3 = -7.93650757867487942473e-05; /*
BF14CE19 9EAADBB7 */
< private static final double Q4 = 4.00821782732936239552e-06; /*
3ED0CFCA 86E65239 */
< private static final double Q5 = -2.01099218183624371326e-07; /*
BE8AFDB7 6E09C32D */
---
> private static final double Q1 = -0x1.11111111110f4p-5; //
> -3.33333333333331316428e-02
> private static final double Q2 = 0x1.a01a019fe5585p-10; //
> 1.58730158725481460165e-03
> private static final double Q3 = -0x1.4ce199eaadbb7p-14; //
> -7.93650757867487942473e-05
> private static final double Q4 = 0x1.0cfca86e65239p-18; //
> 4.00821782732936239552e-06
> private static final double Q5 = -0x1.afdb76e09c32dp-23; //
> -2.01099218183624371326e-07
116,118c116,118
< xsb = hx&0x80000000; /* sign bit of x */
< if(xsb==0) y=x; else y= -x; /* y = |x| */
< hx &= 0x7fffffff; /* high word of |x| */
---
> xsb = hx & 0x8000_0000; /* sign bit of x */
> y = Math.abs(x);
> hx &= 0x7fff_ffff; /* high word of |x| */
121,124c121,124
< if(hx >= 0x4043687A) { /* if |x|>=56*ln2 */
< if(hx >= 0x40862E42) { /* if |x|>=709.78... */
< if(hx>=0x7ff00000) {
< if(((hx&0xfffff)|__LO(x))!=0)
---
> if (hx >= 0x4043_687A) { /* if |x| >= 56*ln2 */
> if (hx >= 0x4086_2E42) { /* if |x| >= 709.78...
> */
> if (hx >= 0x7ff_00000) {
> if (((hx & 0xf_ffff) | __LO(x)) != 0) {
126c126,131
< else return (xsb==0)? x:-1.0;/* exp(+-inf)={inf,-1} */
---
> } else {
> return (xsb == 0)? x : -1.0; /*
> exp(+-inf)={inf,-1} */
> }
> }
> if (x > o_threshold) {
> return huge*huge; /* overflow */
128d132
< if(x > o_threshold) return huge*huge; /* overflow */
131c135
< if(x+tiny<0.0) /* raise inexact */
---
> if (x + tiny < 0.0) { /* raise inexact */
134a139
> }
137,142c142,152
< if(hx > 0x3fd62e42) { /* if |x| > 0.5 ln2 */
< if(hx < 0x3FF0A2B2) { /* and |x| < 1.5 ln2 */
< if(xsb==0)
< {hi = x - ln2_hi; lo = ln2_lo; k = 1;}
< else
< {hi = x + ln2_hi; lo = -ln2_lo; k = -1;}
---
> if (hx > 0x3fd6_2e42) { /* if |x| > 0.5 ln2 */
> if (hx < 0x3FF0_A2B2) { /* and |x| < 1.5 ln2 */
> if (xsb == 0) {
> hi = x - ln2_hi;
> lo = ln2_lo;
> k = 1;}
> else {
> hi = x + ln2_hi;
> lo = -ln2_lo;
> k = -1;
> }
151,152c161
< }
< else if(hx < 0x3c900000) { /* when |x|<2**-54, return x */
---
> } else if (hx < 0x3c90_0000) { /* when |x|<2**-54, return x
> */
154a164,165
> } else {
> k = 0;
156d166
< else k = 0;
164,165c174,176
< if(k==0) return x - (x*e-hxs); /* c is 0 */
< else {
---
> if (k == 0) {
> return x - (x*e - hxs); /* c is 0 */
> } else {
168c179,181
< if(k== -1) return 0.5*(x-e)-0.5;
---
> if (k == -1) {
> return 0.5*(x - e) - 0.5;
> }
170,171c183,187
< if(x < -0.25) return -2.0*(e-(x+0.5));
< else return one+2.0*(x-e);
---
> if(x < -0.25) {
> return -2.0*(e - (x + 0.5));
> } else {
> return one + 2.0*(x - e);
> }
180c196
< t = __HI(t, 0x3ff00000 - (0x200000>>k)); /* t=1-2^-k */
---
> t = __HI(t, 0x3ff0_0000 - (0x2_00000 >> k)); /* t=1-2^-k
> */
-------------
Commit messages:
- JDK-8301396: Port fdlibm expm1 to Java
Changes: https://git.openjdk.org/jdk/pull/12394/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12394&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8301396
Stats: 516 lines in 4 files changed: 497 ins; 12 del; 7 mod
Patch: https://git.openjdk.org/jdk/pull/12394.diff
Fetch: git fetch https://git.openjdk.org/jdk pull/12394/head:pull/12394
PR: https://git.openjdk.org/jdk/pull/12394
