问题
The title summarizes the goal that is more exactly to dynamically retrieve the number of dimensions of MATLAB arrays passed to armadillo matrices.
I would like to change the second and third arguments of mY() and mD() to parametric ones below.
// mat(ptr_aux_mem, n_rows, n_cols, copy_aux_mem = true, strict = false)
arma::mat mY(&dY[0], 2, 168, false);
arma::mat mD(&dD[0], 2, 168, false);
This must be definitely a common use case, but I still could not find a nice way of achieving it for the general case when the number of dimensions of the arrays feeding from MATLAB could be arbitrary (n > 2).
For the matrix (two dimensional) case, I could possibly hack my way around but I feel like that is not elegant enough (probably not efficient either).
IMHO, the way to go must be:
matlab::data::TypedArray<double>
has getDimensions()
member function which retrieves matlab::data::ArrayDimensions
that is fundamentally a std::vector<size_t>
.
Indexing the first and second element of the vector retrieved by getDimensions()
one can retrieve the number of rows and columns, for instance like below.
unsigned int mYrows = matrixY.getDimensions()[0];
unsigned int mYcols = matrixY.getDimensions()[1];
However, with my current setup, I cannot get to call getDimensions()
through pointers/references in the foo()
function of sub.cpp. If it is feasible, I would neither like to create additional temporary objects nor passing other arguments to foo()
. How it possible that way?
Intuition keeps telling me that there must be an elegant solution that way too. Maybe using multiple indirection?
I would highly appreciate any help, hints or constructive comments from more knowledgeable SO members. Thank you in advance.
Setup:
Two C++ source files and a header file:
main.cpp
- contains the general IO interface between MATLAB and C++
- feeds two double arrays and two double const doubles into C++
- it does some Armadillo based looping (this part is not that important therefore omitted) by calling foo()
- returns outp which is a “just a plain” scalar double
- Nothing fancy or complicated.
sub.cpp
- This is only for the foo() looping part.
sub.hpp
- Just a simple header file.
// main.cpp
// MATLAB API Header Files
#include "mex.hpp"
#include "mexAdapter.hpp"
// Custom header
#include "sub.hpp"
// Overloading the function call operator, thus class acts as a functor
class MexFunction : public matlab::mex::Function {
public:
void operator()(matlab::mex::ArgumentList outputs,
matlab::mex::ArgumentList inputs){
matlab::data::ArrayFactory factory;
// Validate arguments
checkArguments(outputs, inputs);
matlab::data::TypedArray<double> matrixY = std::move(inputs[0]);
matlab::data::TypedArray<double> matrixD = std::move(inputs[1]);
const double csT = inputs[2][0];
const double csKy = inputs[3][0];
buffer_ptr_t<double> mY = matrixY.release();
buffer_ptr_t<double> mD = matrixD.release();
double* darrY = mY.get();
double* darrD = mD.get();
// data type of outp is "just" a plain double, NOT a double array
double outp = foo(darrY, darrD, csT, csKy);
outputs[0] = factory.createScalar(outp);
void checkArguments(matlab::mex::ArgumentList outputs, matlab::mex::ArgumentList inputs){
// Create pointer to MATLAB engine
std::shared_ptr<matlab::engine::MATLABEngine> matlabPtr = getEngine();
// Create array factory, allows us to create MATLAB arrays in C++
matlab::data::ArrayFactory factory;
// Check input size and types
if (inputs[0].getType() != ArrayType::DOUBLE ||
inputs[0].getType() == ArrayType::COMPLEX_DOUBLE)
{
// Throw error directly into MATLAB if type does not match
matlabPtr->feval(u"error", 0,
std::vector<Array>({ factory.createScalar("Input must be double array.") }));
}
// Check output size
if (outputs.size() > 1) {
matlabPtr->feval(u"error", 0,
std::vector<Array>({ factory.createScalar("Only one output is returned.") }));
}
}
};
// sub.cpp
#include "sub.hpp"
#include "armadillo"
double foo(double* dY, double* dD, const double T, const double Ky) {
double sum = 0;
// Conversion of input parameters to Armadillo types
// mat(ptr_aux_mem, n_rows, n_cols, copy_aux_mem = true, strict = false)
arma::mat mY(&dY[0], 2, 168, false);
arma::mat mD(&dD[0], 2, 168, false);
// Armadillo calculations
for(int t=0; t<int(T); t++){
// some armadillo based calculation
// each for cycle increments sum by its return value
}
return sum;
}
// sub.hpp
#ifndef SUB_H_INCLUDED
#define SUB_H_INCLUDED
double foo(double* dY, double* dD, const double T, const double Ky);
#endif // SUB_H_INCLUDED
回答1:
One way is to convert it to arma matrix using a function
template<class T>
arma::Mat<T> getMat( matlab::data::TypedArray<T> A)
{
matlab::data::TypedIterator<T> it = A.begin();
matlab::data::ArrayDimensions nDim = A.getDimensions();
return arma::Mat<T>(it.operator->(), nDim[0], nDim[1]);
}
and call it by
arma::mat Y = getMat<double>(inputs[0]);
arma::mat D = getMat<double>(inputs[1]);
...
double outp = foo(Y,D, csT, csKy);
and change foo()
to
double foo( arma::mat& dY, arma::mat& dD, const double T, const double Ky)
来源:https://stackoverflow.com/questions/65868123/dynamic-parameterization-of-armadillo-matrix-dimensions-in-c