Re: [boost] [complex] Feedback and Potential Review Manager

Subject: Re: [boost] [complex] Feedback and Potential Review Manager
From: Christopher Kormanyos (e_float_at_[hidden])
Date: 2012-05-01 17:41:43

>> But then aren't you removing the optimization
>> complex<double> * int that Chris originally proposed ?
>> As your int is promoted to a double. Or are you talking
>> about non-POD integer-like types ?


> No, the promotion is only in calculating the *type of the result*,
> if you look at the actual arithmetic in the example,
> then the real and imaginary components are directly
> multiplied by the arithmetic type.
> John. 

Thanks for the suggestion, John.

Matthieu, I checked John's suggestion with both
(complex * unsigned int) as well as (signed int * complex)
The desired optimization was achieved and numerical
integrity was retained with the multiprecision type
cpp_dec_float.

Matthieu, your code is already looking good!
I don't know if you would like to go with this suggestion
and I can not pressure you to act on it. I do believe, however,
that the suggestion to optimize binary ops with POD will arise
in a potential review. In my opinion, this optimization will
improve your code. So you might want to look into it.
But the decision is yours. I can assist you with the testing of
our multiprecision type if this would help your progress.

So if you want to look into this, you may want to start with:

	1. Binary add, sub, mul, div (complex op POD) and (POD op complex) = 8 template functions

	2. Binary equality/inequality (complex op POD) and (POD op complex) = 4 template functions
	3. Binary add, sub, mul, div (imaginary op POD) and (POD op imaginary) = 8 template functions
The sample below shows  both (complex * POD) and (POD * complex)
You need to be very careful with stuff like (POD / complex)
because the math is a bit more tricky. But you know all that tricky stuff
with the norm, etc.

Best regards, Chris.

/// Returns the value of x times built-in arithmetic type val
template <typename Float, typename Arithmetic>
inline typename enable_if<is_arithmetic<Arithmetic>, complex<typename boost::math::tools::promote_args<Float, Arithmetic>::type> >::type
operator*(const complex<Float>& x, const Arithmetic& val)
{
  typedef complex<typename boost::math::tools::promote_args<Float, Arithmetic>::type> result_type;
  return result_type(x.real() * val, x.imag() * val);
}

/// Returns the value of built-in arithmetic type val times x
template <typename Arithmetic, typename Float>
inline typename enable_if<is_arithmetic<Arithmetic>, complex<typename boost::math::tools::promote_args<Float, Arithmetic>::type> >::type
operator*(const Arithmetic& val, const complex<Float>& x)
{
  typedef complex<typename boost::math::tools::promote_args<Float, Arithmetic>::type> result_type;
  return result_type(x.real() * val, x.imag() * val);
}