MATLAB Compiler

Optimizing Arrays

Scalar Arrays

(fold_scalar_mxarrays) When this optimization is enabled, all constant, scalar-valued array operations are folded at compile time and are stored in a constant pool that is created once at program initialization time. Folding reduces the number of computations that are performed at run-time, thus improving run-time performance.

Scalar folding can dramatically improve the performance of code that is manipulating scalar arrays, but it makes the code less readable. For example:

• function y = foo(x)
  y = 2*pi*x;
  

If you compile this with the -O none option, you get

• ...
  mlfAssign(&y, mclMtimes(mlfScalar(6.283185307179586), 
            mclVa(x, "x")));
  ...
  

Compiling with -O none -O fold_scalar_mxarrays:on, gives

• ...
  mlfAssign(&y, mclMtimes(_mxarray0_, mclVa(x, "x")));
  ...
  

In the optimized case, this code uses _mxarray0_, which is initialized at program start-up to hold the correct value. All constants with the same value use the same mxArray variable in the constant pool.

Optimization Bundles

Nonscalar Arrays