Thanks demetri. Your suggestions are appreciated. You are right I am not a lua jit expert but I do appreciate the feedback and advice. The response times are in seconds. I averaged results across runs so I don't think a few 100ms will make a material difference.
I have been dabbling with FFI to use externally allocated arrays intending to bypass some of the limits imposed by the Lua GC. The results are promising but not yet conclusive. A draft version is at: http://bayesanalytic.com/access-extra-memory-from-lua-jit/ I will l update as I improve the Lua code. The big issue right is that I still have not successfully allocated memory beyond 4 Gig even using the ffi.C.malloc(). Please do send me your suggestions for improvements and I will add them to the article. Let me know if you want attribution.
On 12/12/2014 4:30 PM, demetri wrote:
I am already spreading the word [link to Julia vs LuaJIT post]
This is an interesting comparison to Julia but you might want to
consider two things:
1) if these tests run short enough that milliseconds matter (I can't
tell just from looking at them), then you should get a more precise
timer than os.clock. You may want to ffi.cdef QueryPerformanceCounter
since you seem to be on Windows.
2) Since you're already doing a variant of the Julia code with typed
arrays you might do the same in your LuaJIT example. In particular,
in your sma function you could replace
local tout = {}
with
local tout = {slots = ffi.new("float[?]",numElements)}
or something analogous. That would be the most fair comparison
if I'm understanding your example correctly (if you are new to ffi
code, the wrapper table around ffi.new is one of several ways to
ensure that the allocated memory is anchored for the GC and
lasts beyond the function invocation).
Anyway, I am definitely interested in LuaJIT vs Julia comparisons
as a matter of professional education, so thanks for taking the
time to try this out :) I think this kind of work aimed at educating
newcomers is probably more valuable than monetary donations.
I think most people on this list are more pressed for free time
than they are for a few incremental donations.
Cheers,
Demetri
