From: matz@... (Yukihiro Matsumoto)
Date: 2001-02-14T04:03:14+09:00
Subject: [ruby-talk:10794] Re: perform. of Dir["**/*"]

Hi,

In message "[ruby-talk:10778] perform. of Dir["**/*"]"
    on 01/02/13, "Richard Hensh" <hensh@math.msu.edu> writes:

|Now that someone has straightened me out on the use of **, I have a
|performance question. Running the following script on my C: drive took about
|497 seconds. The drive contains 32701 files. Is this slow?

Slow.  Since it had to create 32701 string objects, GC intervals
became burden.  On my Linux box,

  % ruby -e 'p Dir.glob("**/*").length'

took 1m43sec.  OTOH, 

  % ruby -e 'GC.disable; p Dir.glob("**/*").length'

took 1m13sec.

Then I hacked to reduce memory consumption by using block,
so that now

  % ruby -e 'GC.disable; n = 0; p Dir.glob("**/*"){n+=1}; p n'

takes 4.08sec.  Here's the patch from the latest.

							matz.

--- dir.c~	Mon Nov 20 10:24:22 2000
+++ dir.c	Wed Feb 14 03:29:05 2001
@@ -679,7 +709,14 @@
     char *path;
     VALUE ary;
 {
-    rb_ary_push(ary, rb_tainted_str_new2(path));
+    VALUE str = rb_tainted_str_new2(path);
+
+    if (ary) {
+	rb_ary_push(ary, str);
+    }
+    else {
+	rb_yield(str);
+    }
 }
 
 static void
@@ -753,10 +790,12 @@
     char buffer[MAXPATHLEN], *buf = buffer;
     char *t;
     int nest;
-    VALUE ary;
+    VALUE ary = 0;
 
     Check_SafeStr(str);
-    ary = rb_ary_new();
+    if (!rb_block_given_p()) {
+	ary = rb_ary_new();
+    }
     if (RSTRING(str)->len >= MAXPATHLEN)
 	buf = xmalloc(RSTRING(str)->len + 1);
 
@@ -783,14 +826,6 @@
     }
     if (buf != buffer)
 	free(buf);
-    if (rb_block_given_p()) {
-	long len = RARRAY(ary)->len;
-	VALUE *ptr = RARRAY(ary)->ptr;
-
-	while (len--) {
-	    rb_yield(*ptr++);
-	}
-    }
     return ary;
 }