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Re: help
*To*: mathgroup at yoda.physics.unc.edu
*Subject*: Re: help
*From*: keiper (Jerry Keiper)
*Date*: Mon, 20 Jun 1994 13:50:56 -0500
> My question is the following.
> Should I choose this way:
>
> function[x_Real,y_Real]:=
> N[
> Module[{z,t,aa,bb,cc,...},
> aa=2*Pi*x-y*3.12;
> bb=x-y;
> ...
> ]
> ]
>
> or is it better this other one:
>
> function[x_Real,y_Real]:=
> Module[{z,t,aa,bb,cc,...},
> aa=N[ 2*Pi*x-y*3.12 ];
> bb=N[ x-y ];
> ...
> ]
>
> Or maybe anyother thing?. Here my main interest is the
> computation speed.
It depends on what thos calculations are. Clearly
N[Pi - Pi + 1, 10000]
will be much faster than
N[Pi, 10000] - N[Pi, 10000] + 1
On the other hand, intermediate symbolic growth can become so large
that using N[ ] first is much better:
In[5]:= $RecursionLimit = Infinity
Out[5]= Infinity
In[6]:= N[Nest[Sin, 1, 1000]] // Timing
Out[6]= {6.35 Second, 0.054593}
In[7]:= Nest[Sin, 1., 1000] // Timing
Out[7]= {0.166667 Second, 0.054593}
Jerry B. Keiper
keiper at wri.com
Wolfram Research, Inc.
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