Calc Prime Numbers

[kevin]

Calc Prime Numbers

 While sifting through some old PlayBASIC code snippets, I ran into this one.  The code calc's the prime numbers from zero to a given range.  I'm not sure why I wrote this now, I think it was somebody here. Anyway, there's two versions one's quicker than the other.  Neither are very pretty thought.

PlayBASIC Code: [Select]

;*=------------------------------------------------------------------------=*   
;
;                           >> Calc Prime Numbers <<
;
;                         Code By: Kevin Picone
;
;                               Date: 2/6/2005
;
;           Copyright 2005 by Kevin Picone, All Rights Reserved.
;
;*=-------------------------------------------------------------------------=*   
;
; About:
; ======
;
;     This example shows a couple of ways to generate prime numbers.  I remember
;  writing it for somebody, anyway, here it is.   
;
;*=--------------------------------------------------------------------------=*   

    max=2000


Do
   Cls 0
   inc frames
    Dim table(max)

   t=timer()
      Result=CalcprimesORIG(table(),Max)
   t=timer()-t
   tt1#=tt1#+T
   ShowVals(Result-1)
   print "Time:"+str$(tt1#/frames)
   print "Results:"+str$(result)
   
    Dim table(max)

      t=timer()
         Result=Calcprimes(table(),Max)
      t=timer()-t
      tt2#=tt2#+T
      ShowVals(Result-1)
      print "Time:"+str$(tt2#/frames)
      print "Results:"+str$(result)

   sync
loop   
   
   

Function CalcPRimes(Results(),Max)

   ; Pre-seed 1 & 2 as primes
   results(index)=1
   inc index
   results(index)=2
   inc index
         
     For PrimeTest=3 to max step 2
      PrimeMax=Sqrt(PrimeTEst)
      if ((PrimeTEst/2)*2)<>Primetest
         Found=True
         For TestDiv=3 to PrimeMax step 2
            if ((PrimeTest/TestDiv)*TestDiv)=PrimeTest
               Found=False
               exit
            endif      
         next
         if Found=true
            results(index)=PrimeTest
            inc index
         endif
      endif
   next 

EndFUnction index




Function CalcPRimesORIG(Results(),Max)

   ; Pre-seed 1 & 2 as primes
   results(index)=1
   inc index
   results(index)=2
   inc index
         
     For PrimeTest=3 to max
         Found=True
         For TestDiv=2 to PrimeTest-1
            if ((PrimeTest/TestDiv)*TestDiv)=PrimeTest
               Found=False
               exit
            endif      
         next
         if Found=true
            results(index)=PrimeTest
            inc index
      endif
   next 

EndFUnction index


Function ShowVals(Results)
 t$=""
   For lp=0 to results-1
      t$=t$+digits$(table(lp),5)+","
      inc c
      if c>15
         print trimright$(t$,",")
         t$=""
         c =0
      endif      
   next
   print trimright$(t$,",")
   #print t$
EndFunction

[thaaks]

I remember doing that as a homework in Elan (similar to Pascal) at university 25 years ago  ;D