Lua is faster than Fortran???

[Stefan Behnel]

sturlamolden, 04.07.2010 05:30:
> I was just looking at Debian's benchmarks. It seems LuaJIT is now (on
> median) beating Intel Fortran!
>
> C (gcc) is running the benchmarks faster by less than a factor of two.
> Consider that Lua is a dynamically typed scripting language very
> similar to Python.

Sort of. One of the major differences is the "number" type, which is (by 
default) a floating point type - there is no other type for numbers. The 
main reason why Python is slow for arithmetic computations is its integer 
type (int in Py3, int/long in Py2), which has arbitrary size and is an 
immutable object. So it needs to be reallocated on each computation. If it 
was easily mappable to a CPU integer, Python implementations could just do 
that and be fast. But its arbitrary size makes this impossible (or requires 
a noticeable overhead, at least). The floating point type is less of a 
problem, e.g. Cython safely maps that to a C double already. But the 
integer type is.

So it's not actually surprising that Lua beats CPython (and the other 
dynamic languages) in computational benchmarks.

It's also not surprising to me that a JIT compiler beats a static compiler. 
A static compiler can only see static behaviour of the code, potentially 
with an artificially constructed idea about the target data. A JIT compiler 
can see the real data that flows through the code and can optimise for that.

Stefan