path: root/src/math/nearbyint.c
diff options
authornsz <>2012-03-20 22:49:19 +0100
committernsz <>2012-03-20 22:49:19 +0100
commit91c28f61f43ba029166772e8ac25808ea3c3dc98 (patch)
treea9993bc53514ade564171678339a14470864d8e1 /src/math/nearbyint.c
parent8c6fc860a97f79146bf5c092d5cfb90fa6d9355a (diff)
nearbyint optimization (only clear inexact when necessary)
old code saved/restored the fenv (the new code is only as slow as that when inexact is not set before the call, but some other flag is set and the rounding is inexact, which is rare) before: bench_nearbyint_exact 5000000 N 261 ns/op bench_nearbyint_inexact_set 5000000 N 262 ns/op bench_nearbyint_inexact_unset 5000000 N 261 ns/op after: bench_nearbyint_exact 10000000 N 94.99 ns/op bench_nearbyint_inexact_set 25000000 N 65.81 ns/op bench_nearbyint_inexact_unset 10000000 N 94.97 ns/op
Diffstat (limited to 'src/math/nearbyint.c')
1 files changed, 11 insertions, 12 deletions
diff --git a/src/math/nearbyint.c b/src/math/nearbyint.c
index 714c55ca..7a4c58cf 100644
--- a/src/math/nearbyint.c
+++ b/src/math/nearbyint.c
@@ -1,20 +1,19 @@
#include <fenv.h>
#include <math.h>
-rint may raise inexact (and it should not alter the fenv otherwise)
-nearbyint must not raise inexact
+/* nearbyint is the same as rint, but it must not raise the inexact exception */
-(according to ieee754r section 7.9 both functions should raise invalid
-when the input is signaling nan, but c99 does not define snan so saving
-and restoring the entire fenv should be fine)
+double nearbyint(double x)
+#ifdef FE_INEXACT
+ int e;
-double nearbyint(double x) {
- fenv_t e;
- fegetenv(&e);
+ e = fetestexcept(FE_INEXACT);
x = rint(x);
- fesetenv(&e);
+#ifdef FE_INEXACT
+ if (!e)
+ feclearexcept(FE_INEXACT);
return x;