Hello to everyone.
I'm trying to write "from Python" converters for PETSc objects of the
petsc4py package.
Even if no-one of you uses petsc4py, I think you can help me, if I
explain some basics.
Please, be patient.
I want to make converters for the PETSc Mat type.
Mat is defined as below:
typedef struct _p_Mat* Mat;
where _p_Mat is a structure whose details are not interesting for my problem.
Now, I managed to make a functioning "to Python converter".
My problem is the "from Python converter".
I made a test function
void print_Mat(Mat m) {
... // The implementation is not interesting
};
And I tried to make a "from Python converter" with the code below
(please, look at it ... it's not too long and it's very simple):
struct PETSc_Mat_from_Python {
PETSc_Mat_from_Python() {
static bool do_registration(true);
if (do_registration) {
boost::python::converter::registry::push_back(
&convertible,&construct,boost::python::type_id<Mat>());
do_registration = false;
}
}
static void* convertible(PyObject* obj_ptr) {
// In the line below, PyPetscMat_Get takes a PyObject*
as input and returns a Mat
// (if it succedes) or a PETSC_NULL (if it fails).
This is a function of the petsc4py C API.
// The ownership of the returned Mat is not
transferred (I think)
if (PyPetscMat_Get(obj_ptr) == PETSC_NULL) return NULL;
return obj_ptr;
}
static void construct(PyObject* obj_ptr,
boost::python::converter::rvalue_from_python_stage1_data* data) {
void* storage = (
(boost::python::converter::
rvalue_from_python_storage<Mat>*)data)->storage.bytes;
data->convertible = storage;
// NOTE: The instruction below does not transfer
ownership, but this is not my problem, for now
new (storage) Mat(PyPetscMat_Get(obj_ptr));
}
};
Then, obviously ...
BOOST_PYTHON_MODULE(petsc_ext) {
... some not important lines ...
PETSc_Mat_from_Python(); // Registers the converter
def("print_Mat",print_Mat);
}
The code compiles without errors.
The problem is that when calling "print_Mat" from the Python shell,
the interpreter gives the error:
print_Mat(m) # where m was previously and correctly built from Python
and it is a Python object containing a Mat
Traceback (most recent call last):
File "<stdin>", line 1, in ?
Boost.Python.ArgumentError: Python argument types in
petsc_ext.print_Mat(petsc4py.PETSc.Mat)
did not match C++ signature:
print_Mat(_p_Mat*)
I tried also to modify "void print_Mat(Mat m)" into "void
print_Mat(const Mat m)" or "void print_Mat(const Mat& m)", but the
result is the same.
I tried also to debug the code, but the debugger does not enter into
the "convertible" method, so I guess there is something wrong that I
can't see.
So may be I am missing something for the process of writing a "from
Python converter" for pointer arguments.
Can anyone help me, please ?
--
Michele De Stefano
http://www.linkedin.com/in/micdestefano
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