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Thread: php wrong equation infinity result

  1. #1
    Join Date
    Nov 2012
    Posts
    3

    Angry php wrong equation infinity result

    the equation is

    @N means N^N + N^(N+1) + N^(N+2) + ... + N^(N+9)

    Find the sum of digits in @321

    so i made a little program that first calculate @N

    PHP Code:
    $n 321;
    $res 0;

    for(
    $i=0;$i<10;$i++){

    $res $res bcpow($n,$n+$i);

    }

    echo 
    $res
    i get INF !!!
    so why the result is infinity ?

  2. #2
    Join Date
    Jul 2007
    Location
    Wisconsin
    Posts
    468
    Your results are overflowing.

    321^100 = 4.472015e+250

    that's 250 zeros, and im only raising it to the 100th power. You want to raise it to the 321st power?

    9^321 = 2.050433e+306


    That's as big as Google's calculator will go...

  3. #3
    Join Date
    Aug 2004
    Location
    Ankh-Morpork
    Posts
    19,245
    My guess is you're simply generating numbers too large for PHP to handle? 321^321 = 321 * 321 * 321 * 321...[317 more times!], and just 321^4 = 10,617,447,681.
    "Please give us a simple answer, so that we don't have to think, because if we think, we might find answers that don't fit the way we want the world to be."
    ~ Terry Pratchett in Nation

    eBookworm.us

  4. #4
    Join Date
    Nov 2012
    Posts
    3

    Unhappy thank you for answers

    at first i thought there is something with memory exhausted !

    and when i trying to just add two parts like [ N^N + N^(N+1) ] it also give INF !!!

    but this equation has a solution and now how to solve this equation ??

    this equation is here

    http://tournament.arabnet.me/challenge/

    in web developer challenge

  5. #5
    Join Date
    Aug 2004
    Location
    Ankh-Morpork
    Posts
    19,245
    It might simply be that you need to use bc*() functions for all arithmetic operations, not just the bcpow(). Otherwise you'll be exceeding the max PHP integer size (32 or 64 bit unsigned integer).
    PHP Code:
    $n 321;
    $res 0;
    for(
    $i=0;$i<10;$i++){
      
    $res bcadd($resbcpow($nbcadd($n$i)));
    }
    echo 
    $res
    "Please give us a simple answer, so that we don't have to think, because if we think, we might find answers that don't fit the way we want the world to be."
    ~ Terry Pratchett in Nation

    eBookworm.us

  6. #6
    Join Date
    Nov 2012
    Posts
    3
    Thank you very much

    it's working fine and i got a result

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