star-mc

commit 37b67451efbc4fa5d430c3aab1ad67f7824c51e6
parent 2efd7d71eb5a2d3b500b95482963342205a6c6e0
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Wed, 15 Jul 2015 08:38:53 +0200

Fix a precision issue in the smc_<float|double> sqrt function

When the variance is null one could note a tiny negative value due to
numerical imprecisions. The variance is now clamped to 0 when its value
is a small negative number.

Diffstat:
M
src/smc_type_real.h
 | 
7
+++++--

1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/src/smc_type_real.h b/src/smc_type_real.h
@@ -33,6 +33,8 @@
   #error "Missing the SMC_TYPE_REAL definition"
 #endif
 
+#include <rsys/math.h>
+
 #define SMC_REAL_FUNC__(Func) \
   CONCAT(CONCAT(CONCAT(smc_, SMC_TYPE_REAL), _), Func)
 
@@ -102,8 +104,9 @@ SMC_REAL_FUNC__(divi)(void* result, const void* op0, const size_t op1)
 static void
 SMC_REAL_FUNC__(sqrt)(void* result, const void* value)
 {
-  ASSERT(result && value && *(const SMC_TYPE_REAL*)value >= (SMC_TYPE_REAL)0);
-  *(SMC_TYPE_REAL*)result = (SMC_TYPE_REAL)sqrt(*(const SMC_TYPE_REAL*)value);
+  ASSERT(result && value && *(const SMC_TYPE_REAL*)value >= (SMC_TYPE_REAL)-1.e-6);
+  *(SMC_TYPE_REAL*)result = (SMC_TYPE_REAL)sqrt
+    (MMAX(*(const SMC_TYPE_REAL*)value, (SMC_TYPE_REAL)0.0));
 }
 
 /*******************************************************************************