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| 55 | <H1><A NAME="SECTION0012800000000000000000"> |
| 56 | 10.8 Extensions -- Deriving Better Profilers</A> |
| 57 | </H1> |
| 58 | <A NAME="Profiler_Extensions"></A> |
| 59 | <P> |
| 60 | The <tt class="class">Profile</tt> class of module <tt class="module">profile</tt> was written so that |
| 61 | derived classes could be developed to extend the profiler. The details |
| 62 | are not described here, as doing this successfully requires an expert |
| 63 | understanding of how the <tt class="class">Profile</tt> class works internally. Study |
| 64 | the source code of module <tt class="module">profile</tt> carefully if you want to |
| 65 | pursue this. |
| 66 | |
| 67 | <P> |
| 68 | If all you want to do is change how current time is determined (for |
| 69 | example, to force use of wall-clock time or elapsed process time), |
| 70 | pass the timing function you want to the <tt class="class">Profile</tt> class |
| 71 | constructor: |
| 72 | |
| 73 | <P> |
| 74 | <div class="verbatim"><pre> |
| 75 | pr = profile.Profile(your_time_func) |
| 76 | </pre></div> |
| 77 | |
| 78 | <P> |
| 79 | The resulting profiler will then call <code>your_time_func()</code>. |
| 80 | The function should return a single number, or a list of |
| 81 | numbers whose sum is the current time (like what <tt class="function">os.times()</tt> |
| 82 | returns). If the function returns a single time number, or the list of |
| 83 | returned numbers has length 2, then you will get an especially fast |
| 84 | version of the dispatch routine. |
| 85 | |
| 86 | <P> |
| 87 | Be warned that you should calibrate the profiler class for the |
| 88 | timer function that you choose. For most machines, a timer that |
| 89 | returns a lone integer value will provide the best results in terms of |
| 90 | low overhead during profiling. (<tt class="function">os.times()</tt> is |
| 91 | <em>pretty</em> bad, as it returns a tuple of floating point values). If |
| 92 | you want to substitute a better timer in the cleanest fashion, |
| 93 | derive a class and hardwire a replacement dispatch method that best |
| 94 | handles your timer call, along with the appropriate calibration |
| 95 | constant. |
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| 131 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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