Re: [Gretl-devel] basic Julia support
On Thu, 21 Jan 2016, Riccardo (Jack) Lucchetti wrote:
On Wed, 20 Jan 2016, Allin Cottrell wrote:
> Perhaps we should offer a prize for the first example of actual time-saving
> (and/or improvement in accuracy) in sending a calculation of the sort that
> might be required in gretl out to julia for computation.
Easy: just take Oleh's recursion example.
<hansl>
set echo off
set messages off
function scalar fib(scalar n)
return n<2 ? n : fib(n-1) + fib(n-2)
end function
set stopwatch
eval fib(30)
native = $stopwatch
foreign language=julia
function fib(n)
if n<2
return n
else
return fib(n-1)+fib(n-2)
end
end
println(fib(30))
end foreign
julia = $stopwatch
print native julia
</hansl>
<output>
832040
832040
native = 71.920384
julia = 4.4912745
</output>
For sure, that's an example of something that julia does a lot faster
than gretl. But my notional prize is not yet awarded since if I insert
this native function
<hansl>
function scalar smartfib(scalar n)
if n < 2
return n
endif
scalar r5 = sqrt(5)
return (((1+r5)/2)^n - ((1-r5)/2)^n)/r5
end function
</hansl>
and time it as "native_smart", I get
<output>
832040
832040
832040
native = 35.508119
native_smart = 8.5512991e-05
julia = 0.54034932
</output>
Your example shows that recursion is a _lot_ faster in julia; so now
we want a case where recursion is actually needed.
Allin