I spent some effort with this idea of pre-allocation of Perl hashes. I thought it was cool and that it would do a lot. But I found out differently. In one application, I found that pre-sizing a 128K hash table made almost no significant difference at all versus letting the hash grow "naturally".
The Perl hash function has changed over the years, but the low level C implementation appears to be "solid". The Intel integer multiply has gotten faster over the years and using shifts and addition versus multiply doesn't make as much difference as it used to. Also the low level Perl mem to mem copies appear to be "fast enough" - this more apparent with bigger data sizes to be copied.
My conclusion: With less than 128K keys, don't worry about it unless there is some extreme requirement for this hash.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.
|