From 948006be75947f11d3928e653091109ae5478d99 Mon Sep 17 00:00:00 2001
From: Ben Elliston <bje@air.net.au>
Date: Tue, 19 Aug 2014 21:36:19 +1000
Subject: [PATCH] Add an optional max_processes parameter to
 setMultiProcessing() to control the number of worker processes in the pool. 
 Defaults to None, which leads to one worker for every CPU available (as the
 Python multiprocessing module does).

---
 pyevolve/GPopulation.py | 9 +++++----
 pyevolve/GSimpleGA.py   | 5 +++--
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/pyevolve/GPopulation.py b/pyevolve/GPopulation.py
index 0746dd4..a8b7f19 100644
--- a/pyevolve/GPopulation.py
+++ b/pyevolve/GPopulation.py
@@ -152,13 +152,13 @@ def __init__(self, genome):
       self.allSlots = [self.scaleMethod]
 
       self.internalParams = {}
-      self.multiProcessing = (False, False)
+      self.multiProcessing = (False, False, None)
 
       # Statistics
       self.statted = False
       self.stats = Statistics()
 
-   def setMultiProcessing(self, flag=True, full_copy=False):
+   def setMultiProcessing(self, flag=True, full_copy=False, max_processes=None):
       """ Sets the flag to enable/disable the use of python multiprocessing module.
       Use this option when you have more than one core on your CPU and when your
       evaluation function is very slow.
@@ -168,6 +168,7 @@ def setMultiProcessing(self, flag=True, full_copy=False):
 
       :param flag: True (default) or False
       :param full_copy: True or False (default)
+      :param max_processes: None (default) or an integer value
 
       .. warning:: Use this option only when your evaluation function is slow, se you
                    will get a good tradeoff between the process communication speed and the
@@ -177,7 +178,7 @@ def setMultiProcessing(self, flag=True, full_copy=False):
          The `setMultiProcessing` method.
 
       """
-      self.multiProcessing = (flag, full_copy)
+      self.multiProcessing = (flag, full_copy, max_processes)
 
    def setMinimax(self, minimax):
       """ Sets the population minimax
@@ -385,7 +386,7 @@ def evaluate(self, **args):
       # We have multiprocessing
       if self.multiProcessing[0] and MULTI_PROCESSING:
          logging.debug("Evaluating the population using the multiprocessing method")
-         proc_pool = Pool()
+         proc_pool = Pool(processes=self.multiProcessing[2])
 
          # Multiprocessing full_copy parameter
          if self.multiProcessing[1]:
diff --git a/pyevolve/GSimpleGA.py b/pyevolve/GSimpleGA.py
index b750a86..8f39aa7 100644
--- a/pyevolve/GSimpleGA.py
+++ b/pyevolve/GSimpleGA.py
@@ -383,7 +383,7 @@ def __repr__(self):
         ret += "\n"
         return ret
 
-    def setMultiProcessing(self, flag=True, full_copy=False):
+    def setMultiProcessing(self, flag=True, full_copy=False, max_processes=None):
         """ Sets the flag to enable/disable the use of python multiprocessing module.
         Use this option when you have more than one core on your CPU and when your
         evaluation function is very slow.
@@ -403,6 +403,7 @@ def setMultiProcessing(self, flag=True, full_copy=False):
 
         :param flag: True (default) or False
         :param full_copy: True or False (default)
+        :param max_processes: None (default) or an integer value
 
         .. warning:: Use this option only when your evaluation function is slow, so you'll
                      get a good tradeoff between the process communication speed and the
@@ -424,7 +425,7 @@ def setMultiProcessing(self, flag=True, full_copy=False):
         if type(full_copy) != BooleanType:
             Util.raiseException("Multiprocessing 'full_copy' option must be True or False", TypeError)
 
-        self.internalPop.setMultiProcessing(flag, full_copy)
+        self.internalPop.setMultiProcessing(flag, full_copy, max_processes)
 
     def setMigrationAdapter(self, migration_adapter=None):
         """ Sets the Migration Adapter