Using Bigarrays, most of the problem seems to be solved.
However, I still have an important problem:
Now I define in the Ocaml code a matrix (Bigarray.Array2) "bpsi" and a vector (Bigarray.Array1) "by".
Both are defined using the kind Bigarray.float32 and the layout Bigarray.c_layout.
If I print them in Ocaml, they contains the good values.
Now I call my stub function from Ocaml, written in C: (definef with external ...etc)
let beta = solve_olsr bpsi by
In C, I have:
value solve_olsr(value bpsi, value by){
CAMLparam2(bpsi,by);
int rows = Bigarray_val(bpsi)->dim[0];
int cols = Bigarray_val(bpsi)->dim[1];
...
double * vec_data = Data_bigarray_val(by);
double ** mat_data = Data_bigarray_val(bpsi);
...
print_vector(rows, vec_data);
print_matrix(rows,cols,mat_data);
....
There are two problems :
- First, I need to have a matrix defined with type double **, due to the function I call next, which takes as input a matrix of type double ** and an array of type double *. I guess that Data_bigarray_val only outputs a flat array corresponding to an Array of any dimension. If this is the case, this is not what I want (it seems more difficult to allocate a such a contiguous block in memory when it is big). So is there another function that does the job, i.e. maps a Bigarray.Array2 to double ** with the right allocation ?
Now, when I print the matrix, the programs crashes (Segmentation fault), which seems coherent with the previous interpretation.
- When I print the vector vec_data, it has the right number of elements, but unfortunately all values are 0. Thus I guess there is some problem with the Bigarray.float32 thing. Is it that ?
Thanks,
Odalric
2010/3/4 Odalric-Ambrym Maillard
<odalricambrym.maillard@gmail.com>
Thanks, I was not aware of this relation between Bigarrays and C.
I will try to use this and tell you of it works as I want.
Odalric