.. role:: python(code)
   :language: python


.. index::
   profiling
   profiling; deterministic
   profiling; probabilistic
      

Cpu profiling
-------------

There are two complementary objectives:

+ get a big picture of where the time is spent :python:`cProfile, pstats` (standard) or  :python:`pyinstrument` (external dependency). 
  For comments on `deterministic <https://docs.python.org/3/library/profile.html#what-is-deterministic-profiling>`_ vs 
  `statistical <https://pyinstrument.readthedocs.io/en/latest/how-it-works.html>`_ profiling.
+ monitor the performance of the most important functions (potentially as a function of the input size) with :python:`timeit`. 
  The goal can be to confirm a potential theoretical complexity analysis. 

During an optimization phase, it is mandatory to choose between different solutions based  on empirical evidence. 

.. code-block:: python
   :linenos:
   
   from collections.abc import Callable
   import cProfile
   import io
   from pathlib import Path
   import pstats

   import time
   from timeit import timeit


   import pyinstrument

.. literalinclude:: ../../../../src/tools_methods/profiling/cpu.py
   :pyobject: profile
   :name: profile
   :linenos:    
   :caption: src   

.. literalinclude:: ../../../../src/tools_methods/profiling/cpu.py
   :pyobject: example
   :name: example
   :linenos:    
   :caption: src   


The built-in package ``cProfile`` gives:

.. code-block:: console

      Ordered by: internal time

      Function                                          called...
                                                            ncalls  tottime  cumtime
      {built-in method time.sleep}                      -> 
      test_cpu.py:24(do_something)                      ->       1    0.000    0.010  test_cpu.py:18(single)
                                                                 3    0.000    0.030  test_cpu.py:21(repeated)
      test_cpu.py:21(repeated)                          ->       3    0.030    0.030  {built-in method time.sleep}
      test_cpu.py:18(single)                            ->       1    0.010    0.010  {built-in method time.sleep}
      {method 'disable' of '_lsprof.Profiler' objects}  -> 


which corresponds to the call graph:

.. _`fig:call_graph`:

.. figure:: call_graph.png 
   :width: 300
   :alt: Call graph

   Call graph

the package :python:`pyinstrument` returns:

.. code-block:: console 

   0.040 example  cpu.py:31
   └─ 0.040 do_something  cpu.py:44
      ├─ 0.030 repeated  cpu.py:41
      │  └─ 0.030 sleep  <built-in>
      └─ 0.010 single  cpu.py:38
         └─ 0.010 sleep  <built-in>