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Re: [Public WebGL] WebGL Shader Validation



There is a rather fundamental problem with detecting infinite loops
either by code inspection or simulation. Alan Turing had a few words to
say about that:

        http://en.wikipedia.org/wiki/Halting_problem

It is a mathematical certainty that no "verifier" can possibly detect
whether an arbitary program will eventually halt.

Absolutely the ONLY way out of that trap is to limit our shader
programming language to not be "Turing Complete"...which is a rather
nasty limitation for some kinds of shader algorithm.

Since there is little or no practical use for shader programs that don't
complete within a very small fraction of a second - a one second (or so)
watchdog timer would seem to be the best - and perhaps only - pragmatic
solution.  We could even allow users to set how long the timer would
wait before killing the web page in some 'about:config' page just in
case they want to use WebGL for some kind of non-traditional use (eg
CUDA-like applications).

  -- Steve

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