1. Strange benchmark result for Phix vs Eu 3.1.1
- Posted by lesterb Aug 21, 2017
- 1329 views
I was messing about with file benchmarks and came across a case where Phix is much slower than Eu 3.1. The benchmark requires 100 files to be created on disk, with each file containing 1000000 random bytes. The program for Eu is...
constant BUFFER_SIZE = 10000, SizeOfFile = 1000000, FilesToWrite = 100, randbuff = repeat(255, BUFFER_SIZE) integer cnt, fptr, blen atom tend, tstart tstart = time() for NFiles = 1 to FilesToWrite do fptr = open(sprintf("f%d.dum", NFiles), "wb") cnt = SizeOfFile blen = BUFFER_SIZE while cnt > 0 do if cnt < blen then blen = cnt end if puts(fptr, rand(randbuff[1..blen])) -- EU -- puts(fptr, sq_rand(randbuff[1..blen])) -- PHIX cnt -= blen end while close(fptr) end for tend = time() printf(1, "Execution time = %3.2f\n", tend - tstart)
On my setup with Eu 3.1.1, this runs in about 5 sec. Very reasonable. With Phix 0.7.6 (change the rand call to sq_rand) it takes almost 13 sec. I have verified that it's the sq_rand call that makes the big difference by removing all the file stuff and just generating random data.
The sawn-off Eu benchmark code is...
constant BUFFER_SIZE = 10000, SizeOfFile = 1000000, FilesToWrite = 100, randbuff = repeat(255, BUFFER_SIZE) integer cnt, blen atom tend, tstart sequence p tstart = time() for NFiles = 1 to FilesToWrite do cnt = SizeOfFile blen = BUFFER_SIZE while cnt > 0 do if cnt < blen then blen = cnt end if p = rand(randbuff[1..blen]) -- EU -- p = sq_rand(randbuff[1..blen]) -- PHIX cnt -= blen end while end for tend = time() printf(1, "Execution time = %3.2f\n", tend - tstart)
The timings are now Eu: 4.5 sec, Phix: 12.4 sec.
Since I know in this case that the random buffer has no nested sequences, I wrote my own function which avoids the nested call to sq_rand as follows...
function bsq_rand(object a) for i = 1 to length(a) do a[i] = rand(a[i]) end for return a end function
Using bsq_rand instead of sq_rand in the code above gives Phix: 4.21 sec.
So I know how to improve the Phix benchmark result but it surprised me how big the difference in time is.
Is this related to the other discussion on function calling?
2. Re: Strange benchmark result for Phix vs Eu 3.1.1
- Posted by petelomax Aug 21, 2017
- 1288 views
Since I know in this case that the random buffer has no nested sequences, I wrote my own function which avoids the nested call to sq_rand as follows...
function bsq_rand(object a) for i = 1 to length(a) do a[i] = rand(a[i]) end for return a end function
Using bsq_rand instead of sq_rand in the code above gives Phix: 4.21 sec.
So I know how to improve the Phix benchmark result but it surprised me how big the difference in time is.
In case you didn't know (though I expect you did), the actual definition for sq_rand is in builtins\psqop.e:
global function sq_rand(object a) if atom(a) then return rand(a) end if for i=1 to length(a) do a[i] = sq_rand(a[i]) end for return a end function
Is this related to the other discussion on function calling?
Yes, with another little bugbear: after/with s[i] = <tmp>, the compiler should somehow mark <tmp> as unassigned/zero (since it then is), and not need to test/decref/deallocate it, but it don't...
Anyway, modifying builtins/psqop.e to:
global function sq_rand(object a) if atom(a) then return rand(a) end if for i=1 to length(a) do -- a[i] = sq_rand(a[i]) object ai = a[i] ai = iff(atom(ai)?rand(ai):sq_rand(ai)) a[i] = ai end for return a end function
Then I get RDS Eu (2.4): 3.40s, Phix: 3.48s
Putting a[i] = ai on a separate line allows the nested call to use pbr, otherwise it would double-up on that test/decref/deallocate bugbear (which is still there, not that you could legally remove it for a named temp, ai in this case).
I'll make that change for the next release, to solve this specific problem, but yes, there's room for some more general improvement, somehow.
Regards,
Pete
3. Re: Strange benchmark result for Phix vs Eu 3.1.1
- Posted by lesterb Aug 21, 2017
- 1291 views
Thanks Pete.
I did the mod in my psqop.e and Phix now runs the benchmark faster than Eu - which is as it should be .
I was thinking of using the Win function CryptGenRandom to fill an allocated buffer with random bytes in one shot (which is very fast). I think that may be a legitimate tactic, but my Eu/Phix coding is a bit stale at the moment and I can't think how to get a buffer of bytes output without using more external functions.
Perhaps I'll try it just to see how it performs.
Thanks again.
Regards,
Les
4. Re: Strange benchmark result for Phix vs Eu 3.1.1
- Posted by lesterb Aug 24, 2017
- 1224 views
Just to round off this topic, and for idle interest only, I made a Phix version of the benchmark that uses cryptgenrandom.
It creates 100 files, each containing 1000000 random bytes in 2.06 sec. Not too shabby.