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<H1><A NAME="SECTION0012200000000000000000">
10.2 How Is This Profiler Different From The Old Profiler?</A>
</H1>
<A NAME="Profiler_Changes"></A>
<P>
(This section is of historical importance only; the old profiler
discussed here was last seen in Python 1.1.)

<P>
The big changes from old profiling module are that you get more
information, and you pay less CPU time.  It's not a trade-off, it's a
trade-up.

<P>
To be specific:

<P>
<DL>
<DT><STRONG>Bugs removed:</STRONG></DT>
<DD>Local stack frame is no longer molested, execution time is now charged
to correct functions.

<P>
</DD>
<DT><STRONG>Accuracy increased:</STRONG></DT>
<DD>Profiler execution time is no longer charged to user's code,
calibration for platform is supported, file reads are not done <em>by</em>
profiler <em>during</em> profiling (and charged to user's code!).

<P>
</DD>
<DT><STRONG>Speed increased:</STRONG></DT>
<DD>Overhead CPU cost was reduced by more than a factor of two (perhaps a
factor of five), lightweight profiler module is all that must be
loaded, and the report generating module (<tt class="module">pstats</tt>) is not needed
during profiling.

<P>
</DD>
<DT><STRONG>Recursive functions support:</STRONG></DT>
<DD>Cumulative times in recursive functions are correctly calculated;
recursive entries are counted.

<P>
</DD>
<DT><STRONG>Large growth in report generating UI:</STRONG></DT>
<DD>Distinct profiles runs can be added together forming a comprehensive
report; functions that import statistics take arbitrary lists of
files; sorting criteria is now based on keywords (instead of 4 integer
options); reports shows what functions were profiled as well as what
profile file was referenced; output format has been improved.

<P>
</DD>
</DL>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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