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4 <strong>Search</strong> result quality<br />
Frequency<br />
0 50 150 250<br />
to stay within the goal of 100 ms.<br />
4.5.2 Source matching latency<br />
Histogram of trigram lookup latency<br />
0 10 20 30 40 50 60 70 80 90 100<br />
trigram lookup latency [ms]<br />
Figure 4.3: Histogram of trigram lookup latency<br />
The source matching step is where the potentially matching files from the trigram lookup<br />
are actually searched/matched for the query string.<br />
Due to the complex nature of the source code (a regular expression matcher), it is out<br />
of scope for this work to perform algorithmic optimizations or code optimizations on this<br />
step. This is unlike the trigram lookup, which was small and understandable enough to be<br />
re-implemented in optimized C. Therefore, the regular expression matching of the <strong>Code</strong>search<br />
tools has been used as-is.<br />
Figure 4.4 (page 43) shows that the source matching latency spans a larger range (from 0 ms<br />
up to 200 ms) than the trigram lookup latency. Furthermore, it does not linearly correlate<br />
with the number of potential results (the amount of input files for source matching).<br />
42
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