The function multi_array::resize() returns a multi_array reference. Does it mean that resize can change the memory location of the current multi_array object?
No, the multi-array object it self does not change it position in memory, if you read the code it returns simply (*this) after swapping member fields with another object. But, what can change is the memory location of the actual data, since the data sometimes (always?) is reallocated and copied to the new location. That means that the return value of origin() (i.e. pointer to the first element in memory) can change after resize. Like you, I don't know why the author choose to return a reference to (*this) after resize. Maybe it is to be able to easily keep track of the pointer to memory, as follows boost::multi_array A(....); double* actual_data=A.origin(); ... actual_data=A.resize(...).origin(); But, to be honest, I don't know if this is compelling enough to actually provide such return behavior. Another reason to do this is that, suppose that you want to resize the matrix but you are not interested in keeping the elements as resize tries to do. If you use resize directly then there is a waste in copying elements that you are not interested in, then I am pretty sure that it doesn't try to copy elements if you do: boost::multi_array A(extents[5][5]); A.resize(extents[0][0]).resize(extents[10][10]); //equivalent to A.resize(extents[10][10]); but elements are not preserved. As I tell you, these are wild guesses, I wish one of the authors can explain the reason for that.
can I just do my_array->resize()
yes, this is enough in my opinion.
or I should do my_array=my_array->resize()
this is not necessary. Cheers, Alfredo