OpenEuphoria

1. Dramatic slowdown -ping Rob

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Nov 13, 2004
• 586 views

I've narrowed down the unexpected performance hit I mentioned earlier
today (Re: Contest Update (12-Nov-2004))

If INNER is 27, this completes in 0.27 seconds. If it is 28, it takes
3.19 seconds, over tenfold performance drop. Why?

Does anyone else get these results? You may need to massage the
figures a little to account for memory/cpu differences.

Rob, if you manage to duplicate this performance hit on 2.4, do you
get the same on 2.5?

constant START = time()
constant INNER=28
sequence table
		table=repeat(repeat(0,INNER),1024)
integer used
		used=1

for i=1 to 45000 do
	used+=1
	if used>length(table) then table&=repeat(repeat(0,INNER),1024) end
if
	table[used][5]=used
end for

printf(1, "Elapsed time: %f\n", time() - START)

Regards,
Pete
PS the performance hit disappears if I initialise the table to 40,000
entries

3. Re: Dramatic slowdown -ping Rob

• Posted by Robert Craig <rds at RapidEuphoria.com> Nov 13, 2004
• 554 views

Pete Lomax wrote:
> 
> I've narrowed down the unexpected performance hit I mentioned earlier
> today (Re: Contest Update (12-Nov-2004))
> 
> If INNER is 27, this completes in 0.27 seconds. If it is 28, it takes
> 3.19 seconds, over tenfold performance drop. Why?
> 
> Does anyone else get these results? You may need to massage the
> figures a little to account for memory/cpu differences.
> 
> Rob, if you manage to duplicate this performance hit on 2.4, do you
> get the same on 2.5?
> 
> }}}
<eucode>
> constant START = time()
> constant INNER=28
> sequence table
> 		table=repeat(repeat(0,INNER),1024)
> integer used
> 		used=1
> 
> for i=1 to 45000 do
> 	used+=1
> 	if used>length(table) then table&=repeat(repeat(0,INNER),1024) end
> if
> 	table[used][5]=used
> end for
> 
> printf(1, "Elapsed time: %f\n", time() - START)
> </eucode>
{{{

> 
> Regards,
> Pete
> PS the performance hit disappears if I initialise the table to 40,000
> entries

On my 1.8 GHz Pentium-4 machine with 256 Mb RAM,
running ex.exe:

Euphoria 2.4  27  0.94
              28  1.70

Euphoria 2.5  27  0.05
              28  0.05

I couldn't believe this, so I dumped "table" into a file
and did a diff. There was no difference. The times
seemed reasonable. With 2.5 the prompt came back instantly.
With 2.4 it took a second or so.

I can't really explain this, other than to point out that
sometimes weird performance situations can develop with 
the malloc() heap. 2.5 frees up a lot of front-end data 
before running the back-end, but that couldn't explain everything.
Maybe I put in an optimization that I've forgotten about.

Regards,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com

5. Re: Dramatic slowdown -ping Rob

• Posted by CoJaBo <cojabo at suscom.net> Nov 13, 2004
• 559 views

These are my results on an Athlon 64 2.8Ghz with 2GB RAM:

Intepreter INNER time
exw 2.4    27    0.08
exw 2.4    28    0.08
ex 2.4     27    0.00
ex 2.4     28    9.30

Yeah... I'd call that dramatic...
(CRASH!!) I have to go now, one of the cats
knocked something over, and it sounded like
it broke...

Pete Lomax wrote:
> 
> I've narrowed down the unexpected performance hit I mentioned earlier
> today (Re: Contest Update (12-Nov-2004))
> 
> If INNER is 27, this completes in 0.27 seconds. If it is 28, it takes
> 3.19 seconds, over tenfold performance drop. Why?
> 
> Does anyone else get these results? You may need to massage the
> figures a little to account for memory/cpu differences.
> 
> Rob, if you manage to duplicate this performance hit on 2.4, do you
> get the same on 2.5?
> 
> }}}
<eucode>
> constant START = time()
> constant INNER=28
> sequence table
> 		table=repeat(repeat(0,INNER),1024)
> integer used
> 		used=1
> 
> for i=1 to 45000 do
> 	used+=1
> 	if used>length(table) then table&=repeat(repeat(0,INNER),1024) end
> if
> 	table[used][5]=used
> end for
> 
> printf(1, "Elapsed time: %f\n", time() - START)
> </eucode>
{{{

> 
> Regards,
> Pete
> PS the performance hit disappears if I initialise the table to 40,000
> entries
> 
>

7. Re: Dramatic slowdown -ping Rob

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Nov 14, 2004
• 562 views

On Fri, 12 Nov 2004 22:11:07 -0800, Robert Craig
<guest at RapidEuphoria.com> wrote:

>Pete Lomax wrote:
>> 
>> If INNER is 27, this completes in 0.27 seconds. If it is 28, it takes
>> 3.19 seconds, over tenfold performance drop. Why?
>
>On my 1.8 GHz Pentium-4 machine with 256 Mb RAM,
>running ex.exe:
>
>Euphoria 2.4  27  0.94
>              28  1.70
>
>Euphoria 2.5  27  0.05
>              28  0.05
>
>I couldn't believe this
Absolutely, I'd need to see it before I believed it )
>, so I dumped "table" into a file
>and did a diff. There was no difference. The times
>seemed reasonable. With 2.5 the prompt came back instantly.
>With 2.4 it took a second or so.
>
>I can't really explain this, other than to point out that
>sometimes weird performance situations can develop with 
>the malloc() heap. 2.5 frees up a lot of front-end data 
>before running the back-end, but that couldn't explain everything.
Maybe I triggered a heapCompact, somehow, but I'm not sure why since I
haven't (deliberately) released thousands of unused heap slots

>Maybe I put in an optimization that I've forgotten about.
Wishful thinking, perhaps.

OK, you need to concentrate on 2.5, and you don't need to waste time
on this issue right now (indeed there is zero time pressure on me over
this), but I'd hate to think you drop this as some great "unsolveable
mystery" and never think of it again. If there is a genuine problem
and it has moved (from 27/28), it'll be a _long_ while before anyone
finds it again, and it might be much more serious/much more urgent.

Is there some kind of "API spy" program that can give further stats?

Regards,
Pete

9. Re: Dramatic slowdown -ping Rob

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Nov 14, 2004
• 540 views

On Sat, 13 Nov 2004 08:18:29 -0800, CoJaBo <guest at RapidEuphoria.com>
wrote:

>ex 2.4     27    0.00
>ex 2.4     28    9.30
>
>Yeah... I'd call that dramatic...
Wow, I moaned at 2x slower, that's like 1000-fold.

Given you have some 40 times as much memory as me (and 40 squared is
1600), is it looking more and more like some subtle heap corruption?

Regards,
Pete

11. Re: Dramatic slowdown -ping Rob

• Posted by CoJaBo <cojabo at suscom.net> Nov 14, 2004
• 550 views

Pete Lomax wrote:
> 
> On Sat, 13 Nov 2004 08:18:29 -0800, CoJaBo <guest at RapidEuphoria.com>
> wrote:
> 
> >ex 2.4     27    0.00
> >ex 2.4     28    9.30
> >
> >Yeah... I'd call that dramatic...
> Wow, I moaned at 2x slower, that's like 1000-fold.
On exw there is no noticeable slowdown, I wonder why?
But ex shows a difference of about 9.3, 27 being so
fast is showed 0.00 and 28 being so slow I thought it
crashed...

> 
> Given you have some 40 times as much memory as me (and 40 squared is
> 1600), is it looking more and more like some subtle heap corruption?
I'd try it on the other computers, but none of them have Eu installed,
and the binder keeps saying somthing about cho isn't a command...

> 
> Regards,
> Pete
> 
>

13. Re: Dramatic slowdown -ping Rob

• Posted by Robert Craig <rds at RapidEuphoria.com> Nov 29, 2004
• 610 views

As promised, I looked into the performance issue raised
by Pete Lomax a while back. I don't think there is any
bug in Euphoria itself (ref counts etc.). 
I rather think WATCOM's storage 
allocator for DOS has some very quirky behavior. In exw.exe
I don't use the WATCOM allocator, I use Microsoft's.
I earlier reported no problem with ex.exe for 2.5,
but I think I must have been using exw.exe for 2.5.
exw runs the code below very fast regardless of the 
size of the sequences. People noticed a big slowdown
with ex.exe when moving from 27 to 28. I believe that's because 
I allocate 50% more space when the size becomes 28. 
For speed in handling small sequences, I map to a set of 
standard memory block sizes:
16, 24, 32, 48, 64, 96, 128 bytes, 192 bytes, 256 etc.
I think 27 would need 128, while 28 would need 192.

However, strangely enough, when the size is increased from 28 to 
100, it runs really fast, even though more processing is being
done by Euphoria.

I also noticed that when it runs slow, it actually runs fast
to start with, and then at a certain point it starts taking longer
and longer to allocate a block.

I downloaded the WATCOM source, but I couldn't really understand
how the allocator works. From the comments it did seem like it
was fairly complex, with a lot of special cases, and multiple heaps,
and there was special code added to deal with worst case situations.

Below is Pete's code with a lot of mods to get better information.

-- Time profile based on 167 samples.
-- Left margin shows the percentage of total execution time
-- consumed by the statement(s) on that line.

       |
       |constant START = time()
       |constant INNER=28 --27 good, 28 bad, 50 bad, 100 good, why?
       |sequence table
       |table=repeat(repeat(0,INNER),1024)
       |integer used
       |used=1
       |sequence t1, t2
       |atom t
       |t = time()
       |
       |for i=1 to 45000 do
       |    used+=1
  0.60 |    if remainder(i,3000) = 0 then
  0.60 |        printf(1, "%d: %.2f\n", {i, time()-t})
       |        t = time()
       |    end if
  0.60 |    if used>length(table) then
       |        t1 = repeat(0, INNER)
       |        t2 = repeat(t1, 1024)
  2.40 |        table &= t2
       |    end if
 95.81 |    table[used][1]=99  -- here's where almost all 
       |                       -- the 28-long sequence blocks are allocated
       |end for
       |
       |printf(1, "Elapsed time: %f\n", time() - START)

Regards,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com

15. Re: Dramatic slowdown -ping Rob

• Posted by Mario Steele <eumario at trilake.net> Nov 30, 2004
• 586 views

I have actually found something of much intrest....

I do not have a copy of 2.4 readily at my disposal,
but this test has come up with some.... shall we say,
interesting points.  This problem at hand, may be due
to Heap Corruption as Pete suggested, but it may be
not what your expecting.

I'm running a AMD Athlon XP 2.16 GHz Proccessor with
192 Megs of ram, and for the original source code as
given by Pete, the results are as follows:

ex.exe (27): 0.110000
ex.exe (28): 0.110000

However, I was going to test this with exw.exe, and
needed to throw in a pause before exiting execution,
so I use my normal, while get_key() = -1 do end while
to the end of the code, so I could see the results.

However, I forgot I put this in, when I went to re-test
the code on ex.exe, and found a surprising result.

constant START = time()
constant INNER=27
sequence table
		table=repeat(repeat(0,INNER),1024)
integer used
		used=1

for i=1 to 45000 do
	used+=1
	if used>length(table) then table&=repeat(repeat(0,INNER),1024) end
if
	table[used][5]=used
end for

printf(1, "Elapsed time: %f\n", time() - START)
while get_key() = -1 do end while

One would belive this would return the same result as before,
however, these are the results I got:

ex.exe (27): 2.030000
ex.exe (28): 2.090000

Now, taking from Rob's own admitance, it seems to me, that
it's not the actual execution that's resulting in these
times, but instead, the backend may be corrupting the
heap when it releases the memory before executing the
IL code generated by the frontend.

There's definatly something going on, for the interpreter
to be generating this much of a diffrence between the
original code, to 1 loop inheritance added, with absolutely
no code inside actually executed, except for get_key().

Just letting ya know,
EuMario


Pete Lomax wrote:
> 
> On Sun, 28 Nov 2004 20:29:12 -0800, Robert Craig
> <guest at RapidEuphoria.com> wrote:
> 
> >As promised, I looked into the performance issue raised
> >by Pete Lomax a while back. I don't think there is any
> >bug in Euphoria itself (ref counts etc.). 
> >I rather think WATCOM's storage 
> >allocator for DOS has some very quirky behavior. In exw.exe
> >I don't use the WATCOM allocator, I use Microsoft's.
> Thanks for looking into this. Now I know it's a problem in ex rather
> than exw, I'm no longer overly concerned about it.
> >I earlier reported no problem with ex.exe for 2.5,
> >but I think I must have been using exw.exe for 2.5.
> >exw runs the code below very fast regardless of the 
> >size of the sequences. People noticed a big slowdown
> >with ex.exe when moving from 27 to 28. I believe that's because 
> >I allocate 50% more space when the size becomes 28. 
> >For speed in handling small sequences, I map to a set of 
> >standard memory block sizes:
> >16, 24, 32, 48, 64, 96, 128 bytes, 192 bytes, 256 etc.
> >I think 27 would need 128, while 28 would need 192.
> >
> >However, strangely enough, when the size is increased from 28 to 
> >100, it runs really fast, even though more processing is being
> >done by Euphoria.
> Sounds to me like Watcom has a problem with 192, which is not all that
> surprising since few C programs are likely to allocate tens of
> thousands of blocks of (just) that size. You've probably thought of
> this already, but you might want to consider avoiding the problem in
> ex by removing the 192 size (ie just in ex, leave it in exw and exu)?
> As I said, it does not really bother me personally, but I know that
> "speed is something of an obsession for you".
> 
> Regards,
> Pete