Hello,
I am having trouble creating arma::mat with external writeable auxiliary
memory as class member;
ie:
struct Example {
Example( double *ptr ){
// ..... see provided minimal working example
}
arma::mat ExtPtr; // this is what I would like to have
}
What is it that I am doing wrong? Can someone point to the right direction
which preferably would use externally created memory location, with
encapsulated data structures?
----------------------------------------------------------------------------------------------
example: save it to 'arma_example.cpp', then:
sourceCpp('arma_example.cpp'); arma_example();
----------------------------------------------------------------------------------------------
/*
* Contact: Steven Varga
* steven.va...@gmail.com
* 2013 Toronto, On Canada
*/
#include <stdlib.h>
#include <RcppArmadillo.h>
using namespace std;
// [[Rcpp::depends(RcppArmadillo)]]
struct Example {
Example(double *ptr)
/*
* Initilizationlist wont do
* error: invalid initialization of non-const reference of type
* ‘arma::mat& {aka arma::Mat<double>&}’ from an rvalue of type
* ‘arma::mat {aka arma::Mat<double>
: A(arma::mat(ptr, 3,2, false, true) ){
*/
{
cout<<" creating arma mat, then assigning it to member B " <<endl;
B=arma::mat(ptr+6, 3,2, false, true ); // same area as original B
cout<<"resetting B to 'zeros' should affect datablock outside of
'Example' struct " <<endl;
B.zeros(); // reset to zero
cout<<" printing B inside of Example: "<<endl;
B.print();
cout<<" but B is a copy only, can I have a reference, or B with
original ptr?"<<endl<<endl;
}
//arma::mat& A;
arma::mat B;
};
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
void arma_example() {
double* p = static_cast<double*>( malloc( 30*sizeof(double) ));
arma::mat M(p, 3,10, false, true ); // this works nicely
bzero(p, 30*sizeof(double)); // reset M
M.zeros(); // same as above, but cleaner
arma::mat A(p, 3,1, false, true ); // these work as advertised we
have A,B
arma::mat B(p+6, 3,2, false, true ); // inside ptr area shifted slightly
A.ones(); B.ones(); // lets paint ptr with 'ones'
cout<<"area A and B are ones, rest are zeros as expected"<<endl;
M.print();
cout<< "Now I would like to have the above; encapsulating A,B inside
'Example' "
<< "keeping 'M' and ptr outside of class 'Example' "
<< "by passing 'ptr' in constructor "
<< "initializer list fails to create reference to 'A' from temporary
arma::mat "
<< "when using operator '=' B is initilized with the COPY of ptr
"<<endl;
Example E(p);
cout<<"This is B outside of struct 'Example', expected to be zeros, see
struct Example sonstructor"<<endl;
B.print(); // but B is still 'ones' because '=' copied memory from ptr
// passing B by reference would solve the problem; but that requires
// having B outside of struct Example; and I preferred hiding it; but
using
// RcppArmadillo/matlab syntax inside struct Example on ptr for matrix
multiplication
// and such
// CONTEXT:
// neural network implementation with weights, gradients parameter
unrolling,
// and efficiently passing them to optimizer.
// size: layer[n]*layer[n-1]*layers* sizeof(double)
// roughly:
// ~ 2* 1000*1000*6*8 = 2 * 6*8*10^6 ~= 100 * 10^6 = 100Mbyte
// gets called 10^6~10^7 times per epoch, depending on minibatch size
// epoch := 40 ~ 4000 depending on optimizer
free(p);
}
// EOF
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