Re: lib/46433: tests/lib/libm/t_exp should not use exp() itself

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

The following reply was made to PR lib/46433; it has been noted by GNATS.

From: Jukka Ruohonen <jruohonen%iki.fi@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: lib/46433: tests/lib/libm/t_exp should not use exp() itself
Date: Wed, 30 May 2012 17:19:39 +0300

 On Wed, May 30, 2012 at 11:15:28PM +0900, Tetsuya Isaki wrote:
 > because I don't know about exp2()/exp2f() well...)
 > However, I'm not sure about its appropriate range and
 > appropriate epsilon.
 
 Looks good! Thanks for doing this.
 
 To Tsutsui: by immediate fix I mean that exp(3) (and maybe others?) are
 still completely broken on this architecture, with or without a test. I am
 not sure why systems without FPU even allow libm(3) or expose functions from
 there...
 
 - Jukka.
 
 > 
 > Index: t_exp.c
 > ===================================================================
 > RCS file: /cvsroot/src/tests/lib/libm/t_exp.c,v
 > retrieving revision 1.1
 > diff -u -r1.1 t_exp.c
 > --- t_exp.c  18 Sep 2011 05:19:18 -0000      1.1
 > +++ t_exp.c  30 May 2012 14:09:56 -0000
 > @@ -32,6 +32,22 @@
 >  #include <atf-c.h>
 >  #include <math.h>
 >  
 > +/* y = exp(x) */
 > +static const struct {
 > +    double x;
 > +    double y;
 > +} exp_values[] = {
 > +    {  -10, 0.4539992976248485e-4, },
 > +    {   -5, 0.6737946999085467e-2, },
 > +    {   -1, 0.3678794411714423, },
 > +    { -0.1, 0.9048374180359595, },
 > +    {    0, 1.0000000000000000, },
 > +    {  0.1, 1.1051709180756477, },
 > +    {    1, 2.7182818284590452, },
 > +    {    5, 148.41315910257660, },
 > +    {   10, 22026.465794806718, },
 > +};
 > +
 >  /*
 >   * exp2(3)
 >   */
 > @@ -305,22 +321,23 @@
 >  ATF_TC(exp_product);
 >  ATF_TC_HEAD(exp_product, tc)
 >  {
 > -    atf_tc_set_md_var(tc, "descr", "Test exp(x + y) == exp(x) * exp(y)");
 > +    atf_tc_set_md_var(tc, "descr", "Test some selected exp(x)");
 >  }
 >  
 >  ATF_TC_BODY(exp_product, tc)
 >  {
 >  #ifndef __vax__
 > -    const double x[] = { 0.0, 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7, 8.8 };
 > -    const double y[] = { 8.8, 7.7, 6.6, 5.5, 4.4, 3.3, 2.2, 1.1, 0.0 };
 > +    double x;
 > +    double y;
 >      const double eps = 1.0e-11;
 >      size_t i;
 >  
 > -    for (i = 0; i < __arraycount(x); i++) {
 > +    for (i = 0; i < __arraycount(exp_values); i++) {
 > +            x = exp_values[i].x;
 > +            y = exp_values[i].y;
 >  
 > -            if (fabs(exp(x[i] + y[i]) - (exp(x[i]) * exp(y[i]))) > eps)
 > -                    atf_tc_fail_nonfatal("exp(%0.01f + %0.01f) != exp("
 > -                        "%0.01f) * exp(%0.01f)", x[i], y[i], x[i], y[i]);
 > +            if (fabs(exp(x) - y) > eps)
 > +                    atf_tc_fail_nonfatal("exp(%0.01f) != %18.18e", x, y);
 >      }
 >  #endif
 >  }
 > @@ -413,22 +430,23 @@
 >  ATF_TC(expf_product);
 >  ATF_TC_HEAD(expf_product, tc)
 >  {
 > -    atf_tc_set_md_var(tc, "descr", "Test expf(x+y) == expf(x) * expf(y)");
 > +    atf_tc_set_md_var(tc, "descr", "Test some selected expf(x)");
 >  }
 >  
 >  ATF_TC_BODY(expf_product, tc)
 >  {
 >  #ifndef __vax__
 > -    const float x[] = { 0.0, 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7, 8.8 };
 > -    const float y[] = { 8.8, 7.7, 6.6, 5.5, 4.4, 3.3, 2.2, 1.1, 0.0 };
 > +    float x;
 > +    float y;
 >      const float eps = 1.0e-2;
 >      size_t i;
 >  
 > -    for (i = 0; i < __arraycount(x); i++) {
 > +    for (i = 0; i < __arraycount(exp_values); i++) {
 > +            x = exp_values[i].x;
 > +            y = exp_values[i].y;
 >  
 > -            if (fabsf(expf(x[i] + y[i]) - (expf(x[i]) * expf(y[i]))) > eps)
 > -                    atf_tc_fail_nonfatal("expf(%0.01f + %0.01f) != expf("
 > -                        "%0.01f) * expf(%0.01f)", x[i], y[i], x[i], y[i]);
 > +            if (fabsf(expf(x) - y) > eps)
 > +                    atf_tc_fail_nonfatal("expf(%0.01f) != %18.18e", x, y);
 >      }
 >  #endif
 >  }
 > 
 > ---
 > Tetsuya Isaki <isaki%pastel-flower.jp@localhost / isaki%NetBSD.org@localhost>