Hi,
It seems that julia does not "optimize away" constant expressions in
functions:
julia> f(x)=x+2-2
f (generic function with 1 method)
julia> f(1.e-18)
0.0
This is of course correct in Float64 arithmetics.
But I wonder: In languages like Fortran and C the result of such code
depends on the "optimization flags" used when compiling.
With optimization, the compiler would reduce the function to f(x)=x.
Is there something comparable in Julia?
Another test. Compare
f(x)=x+sin(.34567)
to
const sn=sin(.34567)
g(x)=x+sn
julia> y=0; @time(for i in 1:10^9; y=f(y); end)
22.489526 seconds (2.00 G allocations: 29.802 GB, 3.50% gc time)
julia> y=0; @time(for i in 1:10^9; y=g(y); end)
16.268512 seconds (1000.00 M allocations: 14.901 GB, 2.61% gc time)
It looks like Julia does not optimize even the simplest constant
expressions so that they are evaluated only once.
And why, by all means, does it allocate so much memory for that?
Is there something I overlook?
Best wishes,
Meik
