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Subject: Re: [boost] [math] Does any one interesting in calculating derivative for a expression automatically?
From: Dongfei Yin (yin.dongfei_at_[hidden])
Date: 2009-03-04 05:41:07

Hi John,
  1. I have tried that if you write d(d(d(d(x*x*x*x, x), x), x), x), it
will take a long compile time without optimized. I have do something to
optimized it. I need to write a lot of specialized
template class for most of the operators.
  2. Because of the C++ grammar, I think it can just accept expression
like C++ style. think about operator^, the priority is lower in C++ than
in math.
  3. As I said, high derivative will cost lots of compile time without
"simplify", so you are right, the expression should be simplified. but
at compile time, it is a little difficult to do it, but I'll do my best
to optimized it.


> Good idea, and this is all very neat, but I see a couple of issues:
> 1) Compile times for a compile time derivative is likely to be slow?
> 2) Isn't it easier to just calculate the derivative within a symbolic math
> package and then cut and paste the result into your code (Yacas is free for
> example)?
> 3) What happens for very complex expressions? Can the compile time code
> simplify the resulting derivative so that it is optimally evaluated? Most
> symbolic math packages will have a "simplify" function that does just that,
> without it, code might be very inefficient to evaluate, with it, compile
> times might be way too long :-(
> Regards, John.

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