Dynamic size matrix with QVarLengthArray

[marceloarguello700]

Hi i am making a software for stadistic calculus,
then need to declare a matrix of given size
it is declared only once time and dont resize during the process.

Then need to create a matrix in the rangue of [1 to 10, 100 to 100.000] items.
It only store doubles.

In the begin process declare the matrix,populate with the numbers
and make many calculus, not need to insert o delete items.
Now i do:
double matrix * = new double [dim1 * dim2];
an when need the item (i,j) I do Aij = matrix[i*dim2+j];

Then i have next-> FTH: (2336): *** Fault tolerant heap shim applied to current process. This is usually due to previous crashes. ***

After reading some post, i see that matrix is stored in the heap.
As can give me some problem.
Question:

1. Someone can tell me wich problems?

Reading the doc i see that QVarLengthArray allocates the declared size of
elements on the stack then grow up on the heap.
If use QVarLengthArray, all elements will be in heap

Question:
2) QVarLengthArray will be a better choice o use std::vector with reserve() or which other?

3. To avoid write on copy, how must to use QVarLengthArray,
   wit a pointer or with instance:

QVarLengthArray * ptVLA;
QVarLengthArray VLA;

May be are basic question but i need high performance in my program
Greetings