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nwn-lib erf bottleneck solved (mostly Attn: elven)

 
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Fireboar



Joined: 17 Feb 2008
Posts: 323
PostPosted: Tue Mar 27, 2012 2:06    Post subject: nwn-lib erf bottleneck solved (mostly Attn: elven) Reply with quote
I noticed recently that building a large-ish (over 6k files) module (or hak, or erf) using nwn-lib's Erf class takes a long time (over a minute) - slightly longer than the toolset itself. This didn't seem right, so I did some investigating to find the bottleneck. After my investigation I propose the following patch.

Code:
diff -u a/erf.rb b/erf.rb
--- a/erf.rb   2012-03-27 01:02:35.000000000 +0100
+++ b/erf.rb   2012-03-27 01:03:01.000000000 +0100
@@ -133,12 +133,12 @@
           [c.resref, @content.index(c), c.res_type, 0].pack("a#{fnlen} V v v")
         }.join("")
 
-        pre_offset = 160 + locstr.size + keylist.size + 8 * @content.size
+        offset = 160 + locstr.size + keylist.size + 8 * @content.size
 
         reslist = @content.map {|c|
-          offset = pre_offset +
-            @content[0, @content.index(c)].inject(0) {|sum,x| sum + x.size }
-          [offset, c.size].pack("V V")
+          r = [offset, c.size].pack("V V")
+          offset += c.size
+          r
         }.join("")
 
         offset_to_locstr = 160


The bottleneck is in calculating the offset - the original code sums the size each time and generates sub-arrays. My alteration is simpler: it simply keeps a running offset total, relying on the fact that arrays always enumerate in order. In my tests, this reduced the time taken from over a minute to under 5 seconds.
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elven



Joined: 28 Jul 2006
Posts: 259
Location: Germany
PostPosted: Tue May 01, 2012 23:47    Post subject: Reply with quote
Hi,

thanks for reporting this. :) I was away for a while, and saw this thread just now (the forum didn't notify me either). Feel free to open issues on github next time, too - that's the official bugtracker for this project.

Anyways:

I'm not really sure why I did it that way when I wrote that code. I've committed your changes in master. They'll end up in the new release that I'll get out one of these days - including native ruby1.9 support.
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