On Wed, 1 Feb 2023 07:16:25 GMT, Joe Darcy <da...@openjdk.org> wrote:
>> Another day, another PR to port FDLBIM to Java, this time for the log1p
>> method.
>>
>> Other than using the two-argument form of the __HI method in Java
>> transliteration version rather than C macro, there are no appreciable
>> differences between the original C source in
>>
>> src/java.base/share/native/libfdlibm/s_log1p.c
>>
>> and the transliteration for testing purposes in
>>
>> test/jdk/java/lang/StrictMath/FdlibmTranslit.java
>>
>> The more idiomatic port in
>>
>> src/java.base/share/classes/java/lang/FdLibm.java
>>
>> has had a series of transformation applied layering on the transliteration.
>> The intermediate commits show the progress.
>>
>> The regression tests include probing around input values the implementation
>> uses to decided which branch to take.
>
> Joe Darcy has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - Appease jcheck.
> - Fix typo; improve tests.
PS To provide more context for the review, below are the "diff -w" output for
the original C fdlibm with the transliteration port and the transliteration
port with the more idiomatic port.
$ diff -w Log1p.c Log1p.translit.java
1c1,2
< /* double log1p(double x)
---
> /**
> * Returns the natural logarithm of the sum of the argument and 1.
64a66,77
> static class Log1p {
> private static double ln2_hi = 6.93147180369123816490e-01; /*
> 3fe62e42 fee00000 */
> private static double ln2_lo = 1.90821492927058770002e-10; /*
> 3dea39ef 35793c76 */
> private static double two54 = 1.80143985094819840000e+16; /*
> 43500000 00000000 */
> private static double Lp1 = 6.666666666666735130e-01; /* 3FE55555
> 55555593 */
> private static double Lp2 = 3.999999999940941908e-01; /* 3FD99999
> 9997FA04 */
> private static double Lp3 = 2.857142874366239149e-01; /* 3FD24924
> 94229359 */
> private static double Lp4 = 2.222219843214978396e-01; /* 3FCC71C5
> 1D8E78AF */
> private static double Lp5 = 1.818357216161805012e-01; /* 3FC74664
> 96CB03DE */
> private static double Lp6 = 1.531383769920937332e-01; /* 3FC39A09
> D078C69F */
> private static double Lp7 = 1.479819860511658591e-01; /* 3FC2F112
> DF3E5244 */
> private static double zero = 0.0;
66,92c79
< #include "fdlibm.h"
<
< #ifdef __STDC__
< static const double
< #else
< static double
< #endif
< ln2_hi = 6.93147180369123816490e-01, /* 3fe62e42 fee00000 */
< ln2_lo = 1.90821492927058770002e-10, /* 3dea39ef 35793c76 */
< two54 = 1.80143985094819840000e+16, /* 43500000 00000000 */
< Lp1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
< Lp2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
< Lp3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
< Lp4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
< Lp5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
< Lp6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
< Lp7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
<
< static double zero = 0.0;
<
< #ifdef __STDC__
< double log1p(double x)
< #else
< double log1p(x)
< double x;
< #endif
< {
---
> public static double compute(double x) {
137c124
< __HI(u) = hu|0x3ff00000; /* normalize u */
---
> u = __HI(u, hu|0x3ff00000); /* normalize u */
140c127
< __HI(u) = hu|0x3fe00000; /* normalize u/2 */
---
> u = __HI(u, hu|0x3fe00000); /* normalize u/2 */
158a146
> }
The constants are reformatted as expected and the __HI() C macro used on the
left-hand side of an assignment is replaced by a Java method call.
And port-vs-port:
$ diff -w Log1p.translit.java Log1p.fdlibm.java
67,77c67,75
< private static double ln2_hi = 6.93147180369123816490e-01; /*
3fe62e42 fee00000 */
< private static double ln2_lo = 1.90821492927058770002e-10; /*
3dea39ef 35793c76 */
< private static double two54 = 1.80143985094819840000e+16; /*
43500000 00000000 */
< private static double Lp1 = 6.666666666666735130e-01; /* 3FE55555
55555593 */
< private static double Lp2 = 3.999999999940941908e-01; /* 3FD99999
9997FA04 */
< private static double Lp3 = 2.857142874366239149e-01; /* 3FD24924
94229359 */
< private static double Lp4 = 2.222219843214978396e-01; /* 3FCC71C5
1D8E78AF */
< private static double Lp5 = 1.818357216161805012e-01; /* 3FC74664
96CB03DE */
< private static double Lp6 = 1.531383769920937332e-01; /* 3FC39A09
D078C69F */
< private static double Lp7 = 1.479819860511658591e-01; /* 3FC2F112
DF3E5244 */
< private static double zero = 0.0;
---
> 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 Lp1 = 0x1.5555555555593p-1; //
> 6.666666666666735130e-01
> private static final double Lp2 = 0x1.999999997fa04p-2; //
> 3.999999999940941908e-01
> private static final double Lp3 = 0x1.2492494229359p-2; //
> 2.857142874366239149e-01
> private static final double Lp4 = 0x1.c71c51d8e78afp-3; //
> 2.222219843214978396e-01
> private static final double Lp5 = 0x1.7466496cb03dep-3; //
> 1.818357216161805012e-01
> private static final double Lp6 = 0x1.39a09d078c69fp-3; //
> 1.531383769920937332e-01
> private static final double Lp7 = 0x1.2f112df3e5244p-3; //
> 1.479819860511658591e-01
84c82
< ax = hx&0x7fffffff;
---
> ax = hx & 0x7fff_ffff;
87,94c85,88
< if (hx < 0x3FDA827A) { /* x < 0.41422 */
< if(ax>=0x3ff00000) { /* x <= -1.0 */
< /*
< * Added redundant test against hx to work around VC++
< * code generation problem.
< */
< if(x==-1.0 && (hx==0xbff00000)) /* log1p(-1)=-inf */
< return -two54/zero;
---
> if (hx < 0x3FDA_827A) { /* x < 0.41422 */
> if (ax >= 0x3ff0_0000) { /* x <= -1.0 */
> if (x == -1.0) /* log1p(-1)=-inf */
> return -INFINITY;
96c90
< return (x-x)/(x-x); /* log1p(x<-1)=NaN */
---
> return Double.NaN; /* log1p(x < -1) = NaN */
98,100c92,95
< if(ax<0x3e200000) { /* |x| < 2**-29 */
< if(two54+x>zero /* raise inexact */
< &&ax<0x3c900000) /* |x| < 2**-54 */
---
>
> if (ax < 0x3e20_0000) { /* |x| < 2**-29 */
> if (TWO54 + x > 0.0 /* raise inexact */
> && ax < 0x3c90_0000) /* |x| < 2**-54 */
105,106c100,105
< if(hx>0||hx<=((int)0xbfd2bec3)) {
< k=0;f=x;hu=1;} /* -0.2929<x<0.41422 */
---
>
> if (hx > 0 || hx <= 0xbfd2_bec3) { /* -0.2929 < x < 0.41422 */
> k=0;
> f=x;
> hu=1;
> }
108c107,111
< if (hx >= 0x7ff00000) return x+x;
---
>
> if (hx >= 0x7ff0_0000) {
> return x+x;
> }
>
110c113
< if(hx<0x43400000) {
---
> if (hx < 0x4340_0000) {
122,124c125,127
< hu &= 0x000fffff;
< if(hu<0x6a09e) {
< u = __HI(u, hu|0x3ff00000); /* normalize u */
---
> hu &= 0x000f_ffff;
> if (hu < 0x6_a09e) {
> u = __HI(u, hu | 0x3ff0_0000); /* normalize u */
127,128c130,131
< u = __HI(u, hu|0x3fe00000); /* normalize u/2 */
< hu = (0x00100000-hu)>>2;
---
> u = __HI(u, hu | 0x3fe0_0000); /* normalize u/2 */
> hu = (0x0010_0000 - hu) >> 2;
131a135
>
134,135c138,145
< if(f==zero) { if(k==0) return zero;
< else {c += k*ln2_lo; return k*ln2_hi+c;}}
---
> if (f == 0.0) {
> if (k == 0) {
> return 0.0;
> } else {
> c += k * ln2_lo;
> return k * ln2_hi + c;
> }
> }
137c147,149
< if(k==0) return f-R; else
---
> if (k == 0) {
> return f - R;
> } else {
139a152
> }
143c156,158
< if(k==0) return f-(hfsq-s*(hfsq+R)); else
---
> if (k == 0) {
> return f-(hfsq-s*(hfsq+R));
> } else {
144a160
> }
-------------
PR: https://git.openjdk.org/jdk/pull/12301
