Is there any way to increase 'realmax' in MATLAB?

Question

realmax on my machine is:

1.7977e+308

I know I have to write my code in a way to avoid long integer calculations, but is there

Answer 1

You may find vpa (variable- precision arithmetic) helpful:

R = vpa(A) uses variable-precision arithmetic (VPA) to compute each element of A to at least d decimal digits of accuracy, where d is the current setting of digits.

R = vpa(A,d) uses at least d significant (nonzero) digits, instead of the current setting of digits.

Here's an example how to use it:

>> x = vpa('10^500/20')
ans =
5.0e498

Note that:

• The output x is of symbolic (sym) type. Of course, you shouldn't convert it to double, because it would exceed realmax:

  >> double(x)
  ans =
     Inf
  

• Use string input in order to avoid evaluating large input values as double. For example, this doesn't work

  >> vpa(10^500/20)
  ans =
  Inf
  

  because 10^500 is evaluated as double, giving inf, and then is used as an input to vpa.