changeset:   100167:986184c355e8
user:        Yury Selivanov <yselivanov@sprymix.com>
date:        Fri Feb 05 19:40:01 2016 -0500
files:       Misc/NEWS Objects/longobject.c
description:
Issue #26288: Optimize PyLong_AsDouble.


diff -r f6a89f6cadd0 -r 986184c355e8 Misc/NEWS
--- a/Misc/NEWS	Fri Feb 05 18:26:20 2016 -0500
+++ b/Misc/NEWS	Fri Feb 05 19:40:01 2016 -0500
@@ -165,6 +165,7 @@
 
 - Issue #25660: Fix TAB key behaviour in REPL with readline.
 
+- Issue #26288: Optimize PyLong_AsDouble.
 
 Library
 -------
diff -r f6a89f6cadd0 -r 986184c355e8 Objects/longobject.c
--- a/Objects/longobject.c	Fri Feb 05 18:26:20 2016 -0500
+++ b/Objects/longobject.c	Fri Feb 05 19:40:01 2016 -0500
@@ -2769,6 +2769,13 @@
         PyErr_SetString(PyExc_TypeError, "an integer is required");
         return -1.0;
     }
+    if (Py_ABS(Py_SIZE(v)) <= 1) {
+        /* Fast path; single digit will always fit decimal.
+           This improves performance of FP/long operations by at
+           least 20%. This is even visible on macro-benchmarks.
+        */
+        return (double)MEDIUM_VALUE((PyLongObject *)v);
+    }
     x = _PyLong_Frexp((PyLongObject *)v, &exponent);
     if ((x == -1.0 && PyErr_Occurred()) || exponent > DBL_MAX_EXP) {
         PyErr_SetString(PyExc_OverflowError,