I try to use Julia language from Qt C++ for getting result of SVD function:
jl_value_t *array_type = jl_apply_array_type(jl_float64_type, 2);
jl_array_t *x = jl_alloc_array_2d(array_type, matrixForSvd.rows(), matrixForSvd.cols());
jl_value_t * bol = jl_box_bool(true);
double *p = (double*)jl_array_data(x);
int ndims = jl_array_ndims(x);
size_t size0 = jl_array_dim(x,0);
size_t size1 = jl_array_dim(x,1);
// Fill array with data
for(size_t i=0; i<size1; i++)
for(size_t j=0; j<size0; j++)
p[j + size0*i] = matrixForSvd(j,i);
jl_function_t *func = jl_get_function(jl_base_module, "svd");
jl_tupletype_t *y = (jl_tupletype_t*)jl_call1(func, (jl_value_t*)x);
But when I trying to parse y I get many of trash(it's ok) and only U and V but not S:
double *res = (double*)jl_array_data(y);
for(int t = 0; t < 50; t++){
cout<<res[t]<<endl;
}
Output:
6.94448e-310
1.97626e-323
2.7725e-318
9.88131e-324
9.88131e-324
0
-0.404554 //U
-0.914514
-0.914514
0.404554
0
6.94448e-310
6.94448e-310
1.97626e-323
2.7725e-318
9.88131e-324
9.88131e-324
0
-0.576048 //V
0.817416
-0.817416
-0.576048
0
6.94448e-310
6.94448e-310
1.97626e-323
2.7725e-318
So, how can I correctly get tuple from Julia function like SVD?
svd.cpp:
#include <julia.h>
#include <iostream>
#include <vector>
void print_vector(jl_array_t *vec) {
double *data = (double *) jl_array_data(vec);
size_t n = jl_array_dim(vec, 0);
for(int i = 0; i < n; ++i)
std::cout << data[i] << " ";
std::cout << std::endl;
}
// from column major vector
void print_2d_matrix(jl_array_t *mat) {
double *data = (double *) jl_array_data(mat);
size_t m = jl_array_dim(mat, 0);
size_t n = jl_array_dim(mat, 1);
for(int i = 0; i < m; ++i) {
for(int j = 0; j < n; ++j)
std::cout << data[i+j*m] << " ";
std::cout << std::endl;
}
}
int main() {
// matrix represented as a vector in column-major order
std::vector<double> mat = {
1, 0, 0, 0, 0, 0, 0, 2, 0, 3, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0
};
// initialize Julia
jl_init(NULL);
jl_value_t* dims = (jl_value_t *) jl_eval_string("(4, 5)");
// make sure dims isn't cleaned up by the Julia gc till we're done with it.
JL_GC_PUSH(&dims);
// get the svd function
jl_function_t *svd = jl_get_function(jl_base_module, "svd");
// build a wrapper around the std::vector data to pass our matrix
// to the svd function
jl_value_t* array_type = jl_apply_array_type(jl_float64_type, 2);
jl_array_t *jl_mat = jl_ptr_to_array(array_type, mat.data(), dims, 0);
JL_GC_POP();
// call svd
jl_value_t *ret = jl_call1(svd, (jl_value_t*)jl_mat);
// make sure we don't lose our return data
JL_GC_PUSH1(&ret);
jl_array_t *jl_U = (jl_array_t*)(jl_fieldref(ret, 0));
jl_array_t *jl_S = (jl_array_t*)(jl_fieldref(ret, 1));
jl_array_t *jl_V = (jl_array_t*)(jl_fieldref(ret, 2));
std::cout << "M: " << std::endl;
print_2d_matrix(jl_mat);
std::cout << "U: " << std::endl;
print_2d_matrix(jl_U);
std::cout << "S: " << std::endl;
print_vector(jl_S);
std::cout << "V: " << std::endl;
print_2d_matrix(jl_V);
JL_GC_POP();
jl_atexit_hook(0);
return 0;
}
compile with:
g++ -std=c++14 -fPIC -I$HOME/local/include/julia svd.cpp -L$HOME/local/lib/julia -ljulia
run:
LD_LIBRARY_PATH=$HOME/local/lib/julia JULIA_HOME=$HOME/local/bin ./a.out
output:
M:
1 0 0 0 2
0 0 3 0 0
0 0 0 0 0
0 2 0 0 0
U:
0 1 0 0
1 0 0 0
0 0 0 -1
0 0 1 0
S:
3 2.23607 2 0
V:
-0 0.447214 -0 0
0 0 1 0
1 0 0 0
-0 0 -0 1
0 0.894427 0 0
julia output:
_
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_) | Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type "?help" for help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.4.6 (2016-06-19 17:16 UTC)
_/ |\__'_|_|_|\__'_| |
|__/ | x86_64-redhat-linux
julia> mat = [1 0 0 0 2; 0 0 3 0 0; 0 0 0 0 0; 0 2 0 0 0]
4x5 Array{Int64,2}:
1 0 0 0 2
0 0 3 0 0
0 0 0 0 0
0 2 0 0 0
julia> svd(mat)
(
4x4 Array{Float64,2}:
0.0 1.0 0.0 0.0
1.0 0.0 0.0 0.0
0.0 0.0 0.0 -1.0
0.0 0.0 1.0 0.0,
[3.0,2.23606797749979,2.0,0.0],
5x4 Array{Float64,2}:
-0.0 0.447214 -0.0 0.0
0.0 0.0 1.0 0.0
1.0 0.0 0.0 0.0
-0.0 0.0 -0.0 1.0
0.0 0.894427 0.0 0.0)
julia>