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Suggestion for speeding up Sort (GNU CoreUtils 7.4)
From: |
N . Shamsundar |
Subject: |
Suggestion for speeding up Sort (GNU CoreUtils 7.4) |
Date: |
Sun, 24 May 2009 02:29:45 +0000 (UTC) |
User-agent: |
Loom/3.14 (http://gmane.org/) |
This is a suggestion to speed up Sort, rather than a bug report.
The addition of the code given below at the entry to function mergelines() of
GNU Sort will exploit of the special relation between the arguments (HI - NHI =
T - (NLO + NHI)) to replace the merge operation with a less expensive copy
operation if it so happens that the last element of LO and the first element of
HI are in order with respect to each other. Since the two subarrays are already
sorted, the merging can be accomplished with a simple memory copy.
if(compare (lo - nlo, hi - 1) <= 0){
/* Skip merge */
if (t - lo) do *--t = *--lo; while (--nlo);
return;
}
Sincerely,
N. Shamsundar
Assoc. Professor (Retd.)
University of Houston
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