Matlab defaults to double precision, but single precision is sufficient for many computational problems. In addition, single precision uses half the memory, and is generally twice as fast.
To convert from double to single precision is easy, in that all that is needed is to define the starting variables as single, and then all subsequent variables will default to the variable in each calculation with the lowest precision.
The best approach to define type single is:
X = zeros(10,10, 'single');
The construction: X = single(zeros(10,10)); is four times slower!!
Note that there is no difference between these two constructions for type double given that double precision is the default.
I ran into two problems that dimmed my enthusiasm for single precision.
1) Some Matlab functions will only work with double precision. The interpolation functions are the main examples that I have come across. (It would be great to have some documentation, either informal or formal, listing those Matlab functions that have type limitations. I have yet to find this information on the web.) To use the interpolation functions, you have to convert the input arguments to double, and then convert the output arguments back to single, which is cumbersome, and perhaps troublesome as well, as noted below.
2) A second problem is that the transition back and forth between single and double can cause errors in the limits for the interpolation. I ran across an error where the interpolation started to return nans after conversion to single precision. This problem would not have occured if the interpolation functions were able to work with single precision. That said, it might be possible to set the extrapolation option to "nearest" in order to navigate around the small round-off errors associated with the transition between single and double precision. Of course, this option could only be trusted when the algorithm was known to be fully functional.
For now, I have decided to stick with double precision.
I found very little discussion of this issue on the web. Surely there are others out there with experiences and recommendations about single precision.