MATLAB Programming

11 Improving Performance and Memory Usage
sprintf('The new value of A is %d', A)
function Y = myfun(X)
X(400,:) = 0;
Y = X;
Working with Large Data Sets. Again, when working with large data sets,
you should be aware that MATLAB makes a temporary copy of A if the called
function modifies its value. This temporarily doubles the memory required
to store the array, which causes MATLAB to generate an error if sufficient
memory is not available.
One way to avoid running out of memory in this situation is to use nested
functions. A nested function shares the workspace of all outer functions,
giving the nested function access to data outside of its usual scope. In the
example shown here, nested function setrowval has direct access to the
workspace of the outer function myfun, making it unnecessary to pass a copy
of the variable in the function call. When setrowval modifies the value of A, it
modifies it in the workspace of the calling function. There is no need to use
additional memory to hold a separate array for the function being called, and
therealsoisnoneedtoreturnthemodifiedvalueofA:
function myfun
A = magic(500);
function setrowval(row, value)
A(row,:) = value;
end
setrowval(400, 0);
disp('The new value of A(399:401,1:10) is')
A(399:401,1:10)
end
Data Structures and Memory
Memory requirements differ for the various types of MATLAB data structures.
You may be able to reduce the amount of memory used for these structures by
considering how MATLAB stores them.
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