nobu	2017-12-19 10:08:52 +0900 (Tue, 19 Dec 2017)

  New Revision: 61330

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=61330

  Log:
    Improve Array#- efficiency [Fixes GH-1756]
    
    When doing the difference of a small array with a big one it is not
    efficient in both time and memory to convert the second one to a hash.
    
    From: Ana Mar?\195?\173a Mart?\195?\173nez G?\195?\179mez <ammartinez@s...>

  Modified files:
    trunk/array.c
Index: array.c
===================================================================
--- array.c	(revision 61329)
+++ array.c	(revision 61330)
@@ -4163,7 +4163,7 @@ rb_ary_diff(VALUE ary1, VALUE ary2) https://github.com/ruby/ruby/blob/trunk/array.c#L4163
     ary2 = to_ary(ary2);
     ary3 = rb_ary_new();
 
-    if (RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
+    if (RARRAY_LEN(ary1) <= SMALL_ARRAY_LEN || RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
 	for (i=0; i<RARRAY_LEN(ary1); i++) {
 	    VALUE elt = rb_ary_elt(ary1, i);
 	    if (rb_ary_includes_by_eql(ary2, elt)) continue;

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