Subnormal cancellation correctness

[Stefan Westerfeld <stefan space twc de>]

   Hi!

I've extended subnormals.cc to perform correctness tests as well. It
checks both variants - float and double - offered by BSE. Here is the
patch. Ok to commit? Or should I put the code in a seperate test?

   Cu... Stefan

Index: ChangeLog
===================================================================
RCS file: /cvs/gnome/beast/bse/ChangeLog,v
retrieving revision 1.605
diff -u -p -r1.605 ChangeLog
--- ChangeLog	2 Apr 2006 16:20:29 -0000	1.605
+++ ChangeLog	3 Apr 2006 13:54:17 -0000
@@ -1,3 +1,8 @@
+Mon Apr  3 15:50:14 2006  Stefan Westerfeld <stefan space twc de>
+
+	* tests/subnormals.cc: Added code which verifies that subnormal
+	elimination functions are correct.
+
 Sun Apr  2 18:19:42 2006  Tim Janik  <timj gtk org>
 
 	* bse/Makefile.am: some more dependency and minor build fixes.
Index: tests/subnormals.cc
===================================================================
RCS file: /cvs/gnome/beast/bse/tests/subnormals.cc,v
retrieving revision 1.5
diff -u -p -r1.5 subnormals.cc
--- tests/subnormals.cc	1 Apr 2006 14:42:43 -0000	1.5
+++ tests/subnormals.cc	3 Apr 2006 13:54:17 -0000
@@ -1,5 +1,6 @@
 /* BSE - Bedevilled Sound Engine
  * Copyright (C) 2006 Tim Janik
+ * Copyright (C) 2006 Stefan Westerfeld
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -18,6 +19,7 @@
  */
 #include <bse/bse.h>
 #include <bse/bseieee754.h>
+#include <stdio.h>
 
 #if 1
 inline float    test1 (float v) { return v;     }
@@ -33,6 +35,53 @@ extern float    test4 (float v);
 extern float    test5 (float v);
 #endif
 
+inline double test2d (double v) { return bse_double_zap_denormal (v); }
+inline double test3d (double v) { BSE_DOUBLE_FLUSH_with_cond (v); return v; }
+inline double test4d (double v) { BSE_DOUBLE_FLUSH_with_if (v); return v; }
+inline double test5d (double v) { BSE_DOUBLE_FLUSH_with_threshold (v); return v; }
+
+template<float Func(float)>
+void
+test_correct_subnormal_elimination (const char* algo_name)
+{
+  g_print ("testing algorithm %s for correctness... ", algo_name);
+  fflush (stdout);
+  const int n = 1000000;
+  for (int i = 1; i < n; i++)
+    {
+      float value = BSE_FLOAT_MAX_SUBNORMAL * i / n;
+      g_assert (BSE_FLOAT_IS_SUBNORMAL (value));
+
+      float normalized_positive_value = Func (value);
+      g_assert (!BSE_FLOAT_IS_SUBNORMAL (normalized_positive_value));
+
+      float normalized_negative_value = Func (-value);
+      g_assert (!BSE_FLOAT_IS_SUBNORMAL (normalized_negative_value));
+    }
+  g_print ("PASSED\n");
+}
+
+template<double Func(double)>
+void
+test_correct_subnormal_elimination (const char* algo_name)
+{
+  g_print ("testing algorithm %s for correctness... ", algo_name);
+  fflush (stdout);
+  const int n = 1000000;
+  for (int i = 1; i < n; i++)
+    {
+      double value = BSE_DOUBLE_MAX_SUBNORMAL * i / n;
+      g_assert (BSE_DOUBLE_IS_SUBNORMAL (value));
+
+      double normalized_positive_value = Func (value);
+      g_assert (!BSE_DOUBLE_IS_SUBNORMAL (normalized_positive_value));
+
+      double normalized_negative_value = Func (-value);
+      g_assert (!BSE_DOUBLE_IS_SUBNORMAL (normalized_negative_value));
+    }
+  g_print ("PASSED\n");
+}
+
 int
 main (int   argc,
       char *argv[])
@@ -122,6 +171,16 @@ main (int   argc,
 
   g_print ("subnormal cancellation times: keep=%fs zap=%fs inlined-cond=%fs if-cond=%fs arithmetic=%f\n",
            test1_time, test2_time, test3_time, test4_time, test5_time);
+
+  test_correct_subnormal_elimination<test2>("zap");
+  test_correct_subnormal_elimination<test3>("inlined-cond");
+  test_correct_subnormal_elimination<test4>("if-cond");
+  test_correct_subnormal_elimination<test5>("arithmetic");
+
+  test_correct_subnormal_elimination<test2d>("zap-double");
+  test_correct_subnormal_elimination<test3d>("inlined-cond-double");
+  test_correct_subnormal_elimination<test4d>("if-cond-double");
+  test_correct_subnormal_elimination<test5d>("arithmetic-double");
 
   return 0;
 }
-- 
Stefan Westerfeld, Hamburg/Germany, http://space.twc.de/~stefan