Tests for module 'log2'.

* modules/log2-tests: New file.
* tests/test-log2.c: New file.
* tests/test-log2.h: New file.

4 files changed, 206 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index dc323d7ac6..196cdeef8f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2012-03-11  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'log2'.
+	* modules/log2-tests: New file.
+	* tests/test-log2.c: New file.
+	* tests/test-log2.h: New file.
+
 	New module 'log2'.
 	* lib/math.in.h (log2): New declaration.
 	* lib/log2.c: New file.
diff --git a/modules/log2-tests b/modules/log2-tests
new file mode 100644
index 0000000000..2fc41fc6eb
--- /dev/null
+++ b/modules/log2-tests
@@ -0,0 +1,17 @@
+Files:
+tests/test-log2.c
+tests/test-log2.h
+tests/minus-zero.h
+tests/signature.h
+tests/macros.h
+tests/randomd.c
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-log2
+check_PROGRAMS += test-log2
+test_log2_SOURCES = test-log2.c randomd.c
+test_log2_LDADD = $(LDADD) @LOG2_LIBM@
diff --git a/tests/test-log2.c b/tests/test-log2.c
new file mode 100644
index 0000000000..8c8ae8bdf0
--- /dev/null
+++ b/tests/test-log2.c
@@ -0,0 +1,53 @@
+/* Test of log2() function.
+   Copyright (C) 2010-2012 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2012.  */
+
+#include <config.h>
+
+#include <math.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (log2, double, (double));
+
+#include <float.h>
+
+#include "minus-zero.h"
+#include "macros.h"
+
+#define DOUBLE double
+#define HUGEVAL HUGE_VAL
+#define L_(literal) literal
+#define MANT_DIG DBL_MANT_DIG
+#define MAX_EXP DBL_MAX_EXP
+#define MIN_EXP DBL_MIN_EXP
+#define MINUS_ZERO minus_zerod
+#define LOG2 log2
+#define RANDOM randomd
+#include "test-log2.h"
+
+int
+main ()
+{
+  /* A particular value.  */
+  x = 0.6;
+  y = log2 (x);
+  ASSERT (y >= -0.7369655942 && y <= -0.7369655941);
+
+  test_function ();
+
+  return 0;
+}
diff --git a/tests/test-log2.h b/tests/test-log2.h
new file mode 100644
index 0000000000..5872a790d7
--- /dev/null
+++ b/tests/test-log2.h
@@ -0,0 +1,131 @@
+/* Test of log2*() function family.
+   Copyright (C) 2012 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+static void
+test_function (void)
+{
+  int i;
+  int j;
+  const DOUBLE TWO_MANT_DIG =
+    /* Assume MANT_DIG <= 5 * 31.
+       Use the identity
+         n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
+    (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
+    * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
+
+  /* Pole.  */
+  ASSERT (LOG2 (L_(0.0)) == - HUGEVAL);
+  ASSERT (LOG2 (MINUS_ZERO) == - HUGEVAL);
+
+  /* Integral values.  */
+  {
+    DOUBLE x = L_(1.0);
+    DOUBLE y = LOG2 (x);
+    ASSERT (y == L_(0.0));
+  }
+  {
+    int e;
+    DOUBLE x;
+    DOUBLE y;
+    for (e = 0, x = L_(0.0), y = L_(1.0);
+         e <= MAX_EXP - 1;
+         e++, x = x + L_(1.0), y = y * L_(2.0))
+      {
+        /* Invariant: x = e, y = 2^e.  */
+        DOUBLE z = LOG2 (y);
+        ASSERT (z == x);
+      }
+  }
+  {
+    int e;
+    DOUBLE x;
+    DOUBLE y;
+    for (e = 0, x = L_(0.0), y = L_(1.0);
+         e >= MIN_EXP - 1;
+         e--, x = x - L_(1.0), y = y * L_(0.5))
+      {
+        /* Invariant: x = e, y = 2^e.  */
+        DOUBLE z = LOG2 (y);
+        ASSERT (z == x);
+      }
+  }
+
+  /* Randomized tests.  */
+  {
+    /* Error bound, in ulps.  */
+    const DOUBLE err_bound =
+      (sizeof (DOUBLE) > sizeof (double) ?
+#if defined __i386__ && defined __FreeBSD__
+       /* On FreeBSD/x86 6.4, the 'long double' type really has only 53 bits of
+          precision in the compiler but 64 bits of precision at runtime.  See
+          <http://lists.gnu.org/archive/html/bug-gnulib/2008-07/msg00063.html>.
+          The compiler has truncated all 'long double' literals in log2l.c to
+          53 bits of precision.  */
+       L_(8193.0)
+#else
+       L_(5.0)
+#endif
+       : L_(5.0));
+
+    for (i = 0; i < SIZEOF (RANDOM); i++)
+      {
+        DOUBLE x = L_(16.0) * RANDOM[i] + L_(1.0); /* 1.0 <= x <= 17.0 */
+        DOUBLE y = LOG2 (x);
+        DOUBLE z = LOG2 (L_(1.0) / x);
+        DOUBLE err = y + z;
+        ASSERT (y >= L_(0.0));
+        ASSERT (z <= L_(0.0));
+        ASSERT (err > - err_bound / TWO_MANT_DIG
+                && err < err_bound / TWO_MANT_DIG);
+      }
+  }
+
+  {
+    /* Error bound, in ulps.  */
+    const DOUBLE err_bound =
+      (sizeof (DOUBLE) > sizeof (double) ?
+#if defined __i386__ && defined __FreeBSD__
+       /* On FreeBSD/x86 6.4, the 'long double' type really has only 53 bits of
+          precision in the compiler but 64 bits of precision at runtime.  See
+          <http://lists.gnu.org/archive/html/bug-gnulib/2008-07/msg00063.html>.
+          The compiler has truncated all 'long double' literals in log2l.c to
+          53 bits of precision.  */
+       L_(8193.0)
+#else
+       L_(9.0)
+#endif
+       : L_(9.0));
+
+    for (i = 0; i < SIZEOF (RANDOM) / 5; i++)
+      for (j = 0; j < SIZEOF (RANDOM) / 5; j++)
+        {
+          DOUBLE x = L_(17.0) / (L_(16.0) - L_(15.0) * RANDOM[i]) - L_(1.0);
+          DOUBLE y = L_(17.0) / (L_(16.0) - L_(15.0) * RANDOM[j]) - L_(1.0);
+          /* 1/16 <= x,y <= 16 */
+          DOUBLE z = L_(1.0) / (x * y);
+          /* Approximately  x * y * z = 1.  */
+          DOUBLE err = LOG2 (x) + LOG2 (y) + LOG2 (z);
+          ASSERT (err > - err_bound / TWO_MANT_DIG
+                  && err < err_bound / TWO_MANT_DIG);
+        }
+  }
+}
+
+volatile DOUBLE x;
+DOUBLE y;