It would be great if you could add a paragraph on the aforementioned SimObject
page with your findings.
Andreas
From: Zheng Wu <[email protected]<mailto:[email protected]>>
Reply-To: gem5 users mailing list
<[email protected]<mailto:[email protected]>>
Date: Thursday, 11 July 2013 02:55
To: gem5 users mailing list <[email protected]<mailto:[email protected]>>
Subject: Re: [gem5-users] Python Interaction with C++
Okay ignore my previous question….I got it… Py_Initialize() is a python/c++ API
call provided by the python library.
On 2013-07-10, at 12:47 PM, Jack Wu
<[email protected]<mailto:[email protected]>> wrote:
Hi Andreas,
Thanks for your feedback. I looked over the tutorial and I'm reading about the
SimObjects (http://www.m5sim.org/SimObjects) and there is a call sequence
diagram.
Based on the diagram, the gem5 program starts at the main() function in c++ and
then invokes the python interpreter to deal with the configuration scripts like
you mentioned.
But what I am confused about is how the python is invoked. The functions that
main() calls are:
-initSignals()
-Py_SetProgramName(argv[0])
-Py_Initialize()
-initM5Python()
-m5Main(argc, argv)
-Py_Finalize()
>From comments in source code, the "Py_Initialize()" function is used to
>initialize the embedded python interpreter.
I tried to grep for this function and see where it's implemented and can't find
anything, so how does this function invoke the python interpreter?
(Also the Py_SetProgramName() and Py_Finalize() functions have no
implementation either )
Many Thanks,
Jack
On 2013-07-10, at 12:13 PM, Andreas Hansson
<[email protected]<mailto:[email protected]>> wrote:
Hi Jack,
If you look at the HiPEAC tutorial slides there is an overview of "the big
picture" that shows roughly what is going on. gem5 kicks off a python
interpreter that reads your configuration script, for example se.py. This
script works with a bunch of Python classes to assemble and configure your
system. The System() class you mention is a Python class with a bunch of
knobs (and some of these also have ports).
Once you have got all these configured and assembled, the simulate.py
script goes and turns them into their corresponding C++ classes and passes
the parameters that you set in the Python code. Thus, the Python code is
used to assemble and configure the system (and orchestrate the
simulation), and the C++ classes actually _do_ something during the
simulation itself.
I hope that makes things a bit more clear.
Andreas
On 10/07/2013 16:52, "Jack Wu" <[email protected]<mailto:[email protected]>>
wrote:
Dear Community,
I am new to gem5 and trying to understand gem5 by looking at the source
code starting from the main() function and configuration scripts such as
config/example/se.py.
I don't quite understand the interaction between python and c++. The
following are what I think how it works, please correct me if something
is not right.
1) Python accessing c++ objects:
-SWIG is used to provide the abstraction of c++ object through *.i files
so these objects can be used in python like regular python objects (e.g.
list or dictionary).
- all c++ objects are compiled into a python module called "m5", which is
compiled directly into the gem5 binary (e.g. gem.opt).
-an example of using c++ objects in python would something like (from
se.py): system = System(Š.) // I am guessing System is an object in c++?
2) c++ accessing python objects:
-while looking at the main() function, it calls initM5python(), which in
turn calls a) EmeddedSwig::initAll() and b) EmbeddedPython::initAll()
-I am quite confused about these function calls and their purpose. Are
they trying to access certain objects in python?
-For example: I see an variable called "PyObject" and it's a "typedef
_object PyObject" (in src/sim/init.hh). However "_object" is declared as
"struct _object" and it's not defined anywhere.
-There are a bunch of other variables which are declared but not defined
and it seems to have something to do with python, but I am not sure how
this works
Comments and feedback are much appreciated.
Thanks In Advance,
Jack
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