OpenEuphoria

RE: Sequence Slicing (Was RE: Tough ciphers?)

• Posted by bensler at mail.com Mar 15, 2002
• 409 views

I just made range_find() even faster.
They even out at 100 elements now, clocking at 1.27 secs. More than 100 
elements, and range_find() has the benefit.

Here it is:

function range_find(object x, sequence s, integer pos1, integer pos2)
 integer pos
   pos = pos1
   while pos <= pos2 do
      if equal(x,s[pos]) then exit end if
      pos +=1
   end while
   if pos > pos2 then return 0
   elsif pos = pos1 then return 0
   else return pos
   end if
end function

Chris

bensler at mail.com wrote:
> I should point out, that using sequences of length < 200, range_find() 
> is drastically slower. Using 200 elements or less, range_find() clocks 
> in at 2 seconds. It doesn't seem to drop less than 2 secs.
> fastest time I got for find() was 0.68 using 10 elements.
> 
> Chris
> 
> bensler at mail.com wrote:
> > If I did my test correctly, and you're repetitively searching slices of 
> > a sequence, yes.
> > 
> > Because of your question, I did a bit of further testing. I've 
> > discovered, the turning point between the benefit of find() vs 
> > range_find() is somewhere between 200 to 300 elements.
> > 
> > At 300 elements, iterated 1000000/fl times, range_find() beats find() 
> > with 2.09 vs 2.58 consistently. The higher the number of elements, the 
> > larger the difference.
> > 
> > I haven't tested with nested sequences, or sequences with varied data.
> > 
> > Here are both complete tests:
> > <CONTROL TEST>
> > constant fl=300
> > integer fn
> > fn = open("words.txt","rb")
> > 
> > sequence temp     temp = repeat(0,fl)
> > 
> > for i = 1 to fl do
> >    temp[i] = getc(fn)
> > end for
> > 
> > close(fn)
> > 
> > atom t   t=time()
> > integer count  count = 0
> > integer f,found
> > for i = 1 to 10000000/fl do
> > f=1
> > found=find('\n',temp)
> > while found != 0 do
> >    count +=1
> >    f +=found
> >    found = find('\n',temp[f..length(temp)])
> > end while
> > end for
> > 
> > ? f
> > ? count
> > ? time()-t
> > while get_key()=-1 do end while
> > <END CONTROL TEST>
> > 
> > <range_find() TEST>
> > constant fl = 300
> > integer fn
> > fn = open("words.txt","rb")
> > 
> > sequence temp     temp = repeat(0,fl)
> > 
> > for i = 1 to fl do
> >    temp[i] = getc(fn)
> > end for
> > 
> > close(fn)
> > 
> > function range_find(object x, sequence s, integer pos1, integer pos2)
> >  atom found
> >    found = 0
> >    while not found and pos1 <= pos2 do
> >       found = equal(x,s[pos1]) * pos1
> >       pos1 +=1
> >    end while
> >    return found
> > end function
> > 
> > atom t   t=time()
> > integer count  count = 0
> > integer f,found
> > for i =1 to 10000000/fl do
> > f=0
> > found=find('\n',temp)
> > while found != 0 do
> >    count +=1
> >    f =found+1
> >    found = range_find('\n',temp,f,length(temp))
> > end while
> > end for
> > 
> > ? f
> > ? count
> > ? time()-t
> > while get_key()=-1 do end while
> > <END range_find() TEST>
> > 
> > Chris
> > 
> > Rod Jackson wrote:
> > > ???
<snip>