Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.ruby > #6673

How to make this faster?

Show all headers | View raw

I have this code snippet below:

      p=11
      while p <= sqrtN
        return false if
        n%(p)    == 0 or n%(p+2)  ==0 or n%(p+6)  == 0 or n%(p+8)  ==0 or
        n%(p+12) == 0 or n%(p+18) ==0 or n%(p+20) == 0 or n%(p+26) ==0 or
        n%(p+30) == 0 or n%(p+32) ==0 or n%(p+36) == 0 or n%(p+42) ==0 or
        n%(p+48) == 0 or n%(p+50) ==0 or n%(p+56) == 0 or n%(p+60) ==0 or
        n%(p+62) == 0 or n%(p+68) ==0 or n%(p+72) == 0 or n%(p+78) ==0 or
        n%(p+86) == 0 or n%(p+90) ==0 or n%(p+92) == 0 or n%(p+96) ==0 or
        n%(p+98) == 0 or n%(p+102)==0 or n%(p+110)== 0 or n%(p+116)==0 or
        n%(p+120)== 0 or n%(p+126)==0 or n%(p+128)== 0 or n%(p+132)==0 or
        n%(p+138)== 0 or n%(p+140)==0 or n%(p+146)== 0 or n%(p+152)==0 or
        n%(p+156)== 0 or n%(p+158)==0 or n%(p+162)== 0 or n%(p+168)==0 or
        n%(p+170)== 0 or n%(p+176)==0 or n%(p+180)== 0 or n%(p+182)==0 or
        n%(p+186)== 0 or n%(p+188)==0 or n%(p+198)== 0 or n%(p+200)==0
        p += mod 
      end
      return true

that I can replace with this:

     modk,r=0,1;  p=11
     while (p+modk) <= sqrtN
       return false if ( s=false; res[1..-1].each {|r| s ||= n%(r+modk)==0}; s)
       modk +=mod
     end
     return true

The second snippet is much shorter than the first, but slower.

Is there a way to make the line below faster?

return false if ( s=false; res[1..-1].each {|r| s ||= n%(r+modk)==0}; s)

What I want to do is take an element from res and do -- n%(r+modk)==0. 
If it becomes true I want to return false (immediately if possible). If it's always false for every array element I go through the loop again until the end
condition is met.

Back to comp.lang.ruby | Previous | Next — Next in thread | Find similar

Thread

How to make this faster? jzakiya@gmail.com - 2012-11-13 13:07 -0800
  Re: How to make this faster? Robert Klemme <shortcutter@googlemail.com> - 2012-11-16 19:52 +0100

csiph-web