Author: Dann Corbit
Date: 11:48:54 10/25/99
Go up one level in this thread
On October 25, 1999 at 12:26:37, Michel Langeveld wrote:
>On October 25, 1999 at 10:17:53, Dann Corbit wrote:
>>On October 23, 1999 at 10:36:40, Robert Hyatt wrote:
>>
>>>On October 22, 1999 at 10:03:29, Dann Corbit wrote:
>>>
>>>>Change to binary insertion and you will see a much bigger benefit.
>>>
>>>I tried both (from Knuth Sorting and Searching). Binary is very bad for
>>>lists that have 1-5 entries max. from testing on my machine. Simple
>>>insertion is no faster than the bubble sort I used, but it also turns out
>>>to be no slower either, after testing Crafty over 300 different positions.
>>>
>>>I think I'll leave insertion in, to prevent such discussions in the
>>>future, however. :)
>>I have found a new modification to insertion sort (binary or linear) that will
>>make a large improvement in speed. It has to do with the data movements to
>>perform the actual insertion. By delaying the insertion, I can do all data
>>movements as a single permutation and never move any element more than once. It
>>won't work for big lists though, since the code size is O(n!). With just ten
>>items there are a million leaves in the tree. However, for very small sublists
>>I think it will do very well.
>
>Best way to prove your statement is code it, and prove it's faster!
>Good news by the way.
Got the idea from a web page. Here is an example for n=3. Number of
comparisons is O(n*log(n)). For the left branch (1,2,3) do not move anything.
For (1,3,2) permute the 3 & 2. For (3,1,2) and (2,3,1) we must move all of
them, since none is in the right place, and for (3,2,1) we permute 1 & 3. It is
very simple, really. I have a code generator to write the output, but I think I
can simplify it a lot and use the inline keyword (it's C99). The colon in the
diagram means compare. We don't actually compare twice (e.g. if I test for 1 <
2 I do not have another test for 2<1 {because that only finds equal which is
unlikely and therefore a mostly wasted comparison}
1:2
/ \
< / > \
/ \
2:3 1:3
/ \ / \
< / > \ < / > \
/ \ / \
1,2,3 1:3 2,1,3 2:3
/ \ / \
< / > \ < / > \
/ \ / \
1,3,2 3,1,2 2,3,1 3,2,1
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