[Numpy-discussion] Adopt Mersenne Twister 64bit?

Neal Becker ndbecker2@gmail....
Thu Mar 14 08:25:53 CDT 2013


Robert Kern wrote:

> On Thu, Mar 14, 2013 at 11:00 AM, Neal Becker <ndbecker2@gmail.com> wrote:
>> Robert Kern wrote:
>>
>>> On Wed, Mar 13, 2013 at 12:16 AM, Neal Becker <ndbecker2@gmail.com> wrote:
>>>> I guess I talked to you about 100 years ago about sharing state between
>>>> numpy
>>>> rng and code I have in c++ that wraps boost::random.  So is there a C-api
>>>> for
>>>> this RandomState object I could use to call from c++?  Maybe I could do
>>>> something with that.
>>>
>>> There is not one currently. Cython has provisions for sharing such
>>> low-level access to other Cython extensions, but I'm not sure how well
>>> it works for exporting data pointers and function pointers to general
>>> C/++ code. We could probably package the necessities into a struct and
>>> export a pointer to it via a PyCapsule.
>>>
>>
>> One thing this code doesn't do: it requires construction of the wrapper class
>> passing in a RandomState object.  It doesn't verify you actually gave it a
>> RandomState object.  It's hard to do that.  The problem as I see it is to
>> perform this check, I need the RandomStateType object, which unfortunately
>> mtrand.so does not export.
>>
>> The only way to do it is in c++ code:
>>
>> 1. import numpy.random
>> 2. get RandomState class
>> 3. call it to create RandomState instance
>> 4. get the ob_type pointer.
>>
>> Pretty ugly:
>>
>>   object mod = object (handle<>
>> (borrowed((PyImport_ImportModule("numpy.random")))));
>>   object rs_obj = mod.attr("RandomState");
>>   object rs_inst = call<object> (rs_obj.ptr(), 0);
>>   RandomStateTypeObj = rs_inst.ptr()->ob_type;
> 
> PyObject_IsInstance() should be sufficient.
> 
> http://docs.python.org/2/c-api/object.html#PyObject_IsInstance
> 
> --
> Robert Kern

Thanks!
For the record, an updated version attached.
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