Re: Efficient Evaluation of Image Expressions

On Jul 18, 11:40 pm, Hermann <hermann.rodrig...@gmail.com> wrote:
> I have a language used perform map/image algebra calculations using
> expressions like the following: ...


> Simple expressions, like the one above, have good performance, but if
> the expression gets more complicated, the evaluation process becomes
> painfully slow. Any advice?


      Well, you can easily compile it to C/C++ - change 'abs' to 'fabs',
and 'if x then y else z' to '((x)?(y):(z))', and create a function
with the given parameters that returns the corresponding value. This
translation can be done in one pass on the tree, but you might need to
add the function header at a later stage if you do not know the number
of parameters in advance. Compile this function, link it to your
module or load it from a dynamic library (if you want to compile it as
a part of computation), and call it whenever you need evaluation.


If you do not know the number of parameters, and this number can be
very large, you might need a bit of inlined assembly to put the
corresponding values on the stack, or alternatively pass the
parameters as an array.


      Michael

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