take an early exit when gvprintdouble-ing a "0"

In large graphs, the value being printed is frequently zero and the snprintf in
this function shows up as a minor hotspot. Profiling with
tests/regression_tests/large/long_chain this drops the total snprintf calls
within gvprintdouble from 924019 to 858017. This lowers the contributing runtime
of gvprintdouble to overall execution from 28.89% to 28.12%.

diff --git a/lib/gvc/gvdevice.c b/lib/gvc/gvdevice.c
index 03a348d0261e88bf8025737c08fd26371dc0cc69..145f99a7f8c5e3d0bd4fe6c51d210592781c24e6 100644 (file)
--- a/lib/gvc/gvdevice.c
+++ b/lib/gvc/gvdevice.c
@@ -562,7 +562,8 @@ void gvprintdouble(GVJ_t * job, double num)
     // Prevents values like -0
     if (num > -0.00000001 && num < 0.00000001)
     {
-        num = 0;
+        gvwrite(job, "0", 1);
+        return;
     }
 
     char buf[50];