[En-Nut-Discussion] Problems using global variables and/or floating point numbers on Nut/Os (using ethernut 5)

Ole Reinhardt ole.reinhardt at embedded-it.de
Wed May 30 14:29:32 CEST 2012


> I have managed to transfer and run a small example optimization on the
> board, but scaling up the problem failed. The code managed to run, but the
> optimization did not converge.
> As I see it, there might be two problems. Numerical issues or the size of
> the problem.
> What prescision are used on the Ethernut? How many digits?

That depends on the datatype you use. (float, double, ?)
For a double the IEEE 754 standard says 53bit for the fractional part,
which means more or less 16 digits.

> Is there a limit for the size of global variables?

In general I would suggest not to use that much (or large) global
variables but allocate memory from the heap to save your variables in.




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