How much memory is required to store a matrix using the armadillo linear algebra package?

Question

I am getting the same value on using the sizeOf operator for a matrix of size 100*100 and 1*1 respectively.

mat A(100,100),B(1,1);
A.randu();
B.randu();
cout<<"Memory requested for A:"<<sizeOf(A);
cout<<"Memory requested for B:"<<sizeOf(B);

Output:
Memory requested for A:160
Memory requested for B:160

Well how do I get the actual memory required by the code for each variable A,B.

What is `sizeOf`? Is it some function in the Armadillo library? The type `mat` only stores pointers to the memory that it allocates. There's probably some member function that returns the number of elements in the matrix being managed by a `mat` instance. Multiply the number returned by that with the size of each matrix element. — Praetorian, Apr 19 '15 at 01:21
@Raw N : It returns only 160 , whenever I use sizeOf(). For both variable A and B — backcoder, Apr 19 '15 at 01:25
possible duplicate of [sizeof() a vector](http://stackoverflow.com/questions/2373189/sizeof-a-vector) — Dirk Eddelbuettel, Apr 20 '15 at 11:45

score 2 · Accepted Answer · answered Apr 19 '15 at 02:18

2

The mat type stores an array of doubles, so to get the size of the array as bytes:

A.n_elem * sizeof(double)

The total amount of memory used by A is sizeof(A) + (A.n_elem * sizeof(double)).

answered Apr 19 '15 at 02:18

mtall

1 Answers1