Re: lib/49256: exp2f subtests 9 and 10 of lib/libm/t_exp/exp2_values test case failing

[Tetsuya Isaki <isaki%pastel-flower.jp@localhost>]

The following reply was made to PR lib/49256; it has been noted by GNATS.

From: Tetsuya Isaki <isaki%pastel-flower.jp@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: lib-bug-people%netbsd.org@localhost,
	gnats-admin%netbsd.org@localhost,
	netbsd-bugs%netbsd.org@localhost, gson%gson.org@localhost
Subject: Re: lib/49256: exp2f subtests 9 and 10 of lib/libm/t_exp/exp2_values test case failing
Date: Sun, 05 Oct 2014 12:17:42 +0900

 According to Makoto Kamada's analisys,
 it's a mistake to share the expected value of exp2f(7.7)
 with the expected value of exp2(7.7) in tests/lib/libm/t_exp.c.
 
 This test runs exp2f((float)7.7) = 207.93658...
 but the expected value was calculated by exp2((double)7.7) = 207.93661...
 This problem is only actualized with the case of 7.7 and 8.8,
 but the other cases (1.1 - 6.6) has the same problem.
 
 Here is a sample code to help to understand.
 
 % cat a.c
 #include <stdio.h>
 #include <stdint.h>
 #include <math.h>
 
 int main(int ac, char *av[])
 {
     float a;
     float b;
 
     float f = 7.7;
     double d = 7.7;
 
     a = (float)exp2((double)f);
     b = (float)exp2(d);
     printf("exp2((float)7.7)  = %8.8g (0x%08x)\n", a, *(uint32_t*)&a);
     printf("exp2((double)7.7) = %8.8g (0x%08x)\n", b, *(uint32_t*)&b);
 
     return 0;
 }
 % gcc a.c -lm && ./a.out
 exp2((float)7.7)  = 207.93658 (0x434fefc4)
 exp2((double)7.7) = 207.93661 (0x434fefc6)
 %
 ---
 Tetsuya Isaki <isaki%pastel-flower.jp@localhost / isaki%NetBSD.org@localhost>