Re: Symbolic pkg vpa trig speed

[Daniel J Sebald]

On 07/06/2016 09:02 PM, LachlanA wrote:
> Colin Macdonald-2 wrote
> > x = rand(10, 10);
> >
> > % make vpa objects from x in 16, 32, 48 (of course these will not
> > magically have extra precision, its just for timing)
> > xv16 = vpa(x, 16);
> > xv32 = vpa(x, 32);
> > xv48 = vpa(x, 48);
> >
> > tic; sin(x); toc
> > Elapsed time is 0.000461817 seconds.
> > tic; sin(xv16); toc
> > Elapsed time is 0.156639 seconds.
> > tic; sin(xv32); toc
> > Elapsed time is 0.118703 seconds.
> > tic; sin(xv48); toc
> > Elapsed time is 0.175145 seconds.
> >
> > The xv16 = bit seems take longer than I expect...
>
> If the xv16 case was the first time sin was called for a symbolic variable,
> the time may include loading some code into memory, or other initialization.
> What happens if you do them in the reverse order?

Also, that native width of the CPU variables is likely 32 so there may 
be less machine cycles needed for 32 if 16-bit require rounding or 
something.  Try cputime() rather than clock time too:

stime = cputime();
<test code>
cputime() - stime

Dan