MATLAB: Is there a faster way to cube a array

arrayoperation

Hi everyone
I have an array A whose size is 80000 x 4 x 4.
In order to calculate the cube of each element of A, I am doing
B=A.*A.*A;
Is there a faster way to calculate the cube of each element? Thanks in advance,

Best Answer

On my i5, Matlab R2018b:
tic; y = x.^3; toc
% Elapsed time is 0.109015 seconds.
tic; y = x.*x.*x; toc
% Elapsed time is 0.002039 seconds.
tic; y = Power3(x); toc
% Elapsed time is 0.005729 seconds.
where Power3 is a C-mex:
#include "mex.h"
// Main function ===============================================================
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
  size_t ndim, n;
  const size_t *dims;
  double *x, *y;
  
  ndim = mxGetNumberOfDimensions(prhs[0]);
  dims = mxGetDimensions(prhs[0]);
  n    = mxGetNumberOfElements(prhs[0]);
  x    = mxGetPr(prhs[0]);
  
  plhs[0] = mxCreateUninitNumericArray(ndim, dims, mxDOUBLE_CLASS, mxREAL);
  
  y = mxGetPr(plhs[0]);
  while (n--) {
     *y++ = *x * *x * *x;
     x++;
  }
}
This means: No, x .* x .* x is realy fast already.
Related Question