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

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

At Tue, 29 May 2012 11:50:04 +0000 (UTC),
Jukka Ruohonen wrote:
>  That is one option sure. But if there is no immedate fix available, we
>  likely want to count these cases as expected failures. So I think we can put
>  something like the following to the beginning of these cases:
>  
>       if (exp(1.0) == 0.0) {
>               atf_tc_expect_fail("PR lib/46433");
>               atf_tc_fail("exp(1.0) = 0.0");
>       }
>  
>       [start the actual test]

How about this?  (At first I rewrote about exp()/expf()
because I don't know about exp2()/exp2f() well...)
However, I'm not sure about its appropriate range and
appropriate epsilon.

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>