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From: Jason House (jhouse_at_[hidden])
Date: 20030424 09:56:30
Well, take erf using a single parameter for precision
template <precision = 0.00001>
double erf{};
Then in usage somewhere...
{
double x2 = erf<0.01>(0);
double x5 = erf(0);
cout << round(x2*100)/100.0 << round(x2*1E5)*1E5 << endl;
cout << round(x5*100)/100.0 << round(x5*1E5)*1E5 << endl;
}
Possible output:
1.00 0.99583
1.00 1.00000
The idea is that erf<0.01> only gives a result accurate to 2 decimal
places, while erf or erf<0.00001> gives a result accurate to 5 decimal
places.
That's the basic idea I tried to convey.
Getting multiple performance parameters in would be tougher... and I'm
unsure as to which would be most useful to people... I could imagine
something like trying to specify a time bound and a minimum precision...
possibly causing a compiletime error if there is no available
implementation that can achieve it. Of course, the defining of a time
bound is tricky... As far as precision, an integer number of decimal
places would probably be easier from the implementation standpoint.
Gabriel Dos Reis wrote:
>
> Jason House <jhouse_at_[hidden]> writes:
>
> [...]
>
>  Well, *practical* can mean a number of things to different people.
>  Maybe performance constraints should be template parameters with default
>  values?
>
> Once, you have defined meaning for "perfomance" and workable proposal
> I'd be glad to consider it.
>
>  One possibility being precision?
>
> Could you elaborate on this please?
>
>  Gaby
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