Add more information about random numbers (cf NeuralEnsemble#621)

doc/conf.py

@@ -71,7 +71,7 @@ class MockNESTModule(mock.Mock):
 # General information about the project.
 project = u'PyNN'
 authors = u'the PyNN community'
-copyright = u'2006-2017, ' + authors
+copyright = u'2006-2019, ' + authors
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
@@ -80,7 +80,7 @@ class MockNESTModule(mock.Mock):
 # The short X.Y version.
 version = '0.9'
 # The full version, including alpha/beta/rc tags.
-release = '0.9.3'
+release = '0.9.4.dev'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.

doc/random_numbers.txt

@@ -57,6 +57,13 @@ simulation. This independence can be computationally costly, however, so it is
 possible to set *parallel_safe=False*, accepting that the results will be
 dependent on the number of nodes, in order to get better performace.
 
+.. note:: if you do not provide a seed, PyNN will provide one for you, the
+          same each time. This means that running the same simulation several
+          times will use identical random numbers each time, so if you want
+          to have different random numbers on different runs, you must
+          provide your own seed and change it (or randomly generate it)
+          each time.
+
 .. note:: *parallel_safe* may or may not have any effect when using
           a :class:`~pyNN.random.NativeRNG`, depending on the simulator.
 
@@ -135,4 +142,12 @@ arguments returns a single number, not an array:
           digits but the numbers in the array have full precision.
 
 
+SpikeSourcePoisson
+==================
+
+The :class:`SpikeSourcePoisson` model is currently an exception to the situation outlined above.
+It ought to take an `rng` argument, but at present this is not supported, and the model uses the
+global random number generator seed, as set in the :func:`setup()` function.
+
+
 .. _`GNU Scientific Library random number generators`: http://pygsl.sourceforge.net/reference/pygsl/module-pygsl.rng.html