Re: how to speed up program dealing with large numbers?

Well, Thank you everyone for all your help and info. Incase anyone was wondering here is how my code looks now:

#!/usr/bin/perl

use strict;
use warnings;

my %cache;
sub fib {
    my $n = shift;
    return $n if $n < 2;
    return ( $cache{ $n - 1 } ||= fib($n - 1) )
         + ( $cache{ $n - 2 } ||= fib($n - 2) );
}

print "Fibonnaci Fun\n\n";

print "Pick a number that represents which value of the Fibonnaci sequ
+ence you want to start with\n";
print "ie: 1 would be 1, and 2 would be 1, and 3 would be 2 and so on.
+\n"; 
print "Your choice: ";
chomp(my $value = <>);

print "\nNow pick a number to repesent the range you want.\n";
print "If you want to use values 1 through 10 you you need only enter 
+10,\n";
print "assuming of course you entered 1 above.\n";
print "Your choice: ";
chomp(my $temp = <>);

my $range = $value + $temp;

my $phiApprox;
my $fibValue1;
my $fibValue2;

for my $i ($value .. $range){
  $fibValue1 = fib($i);
  $fibValue2 = fib($i - 1);

  $phiApprox = 0 if($i <= 1);
  $phiApprox = $fibValue1 / $fibValue2 if($i >= 2);

  print "\n";
  print "$fibValue1 / $fibValue2 = $phiApprox";
}

print "\n";
[download]

Comment on Re: how to speed up program dealing with large numbers? Download Code

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Re^2: how to speed up program dealing with large numbers? by GrandFather (Saint) on Mar 22, 2010 at 20:03 UTC
A slight tidy up: #!/usr/bin/perl use strict; use warnings; use bignum; print "Fibonnaci Fun\n\n"; print "Pick a number that represents which value of the Fibonnaci sequ +ence you want to start with\n"; print "ie: 1 would be 1, and 2 would be 1, and 3 would be 2 and so on. +\n"; print "Your choice: "; chomp (my $start = <>); print "\nNow pick a number to repesent the range you want.\n"; print "If you want to use values 1 through 10 you you need only enter +10,\n"; print "assuming of course you entered 1 above.\n"; print "Your choice: "; chomp(my $range = <>); print "\n"; for my $fibNum ($start .. $start + $range){ my $fibValue1 = fib($fibNum); my $fibValue2 = fib($fibNum - 1); my $phiApprox = $fibNum <= 1 ? '***' : $fibValue1 / $fibValue2; print "$fibValue1 / $fibValue2 = $phiApprox\n"; } my %cache; sub fib { my ($n) = @_; return $n if $n < 2; --$n; return ($cache{$n} \|\|= fib($n)) + ($cache{$n - 1} \|\|= fib($n - 1)) +; } [download] Prints (for input numbers 90, 10): Fibonnaci Fun Pick a number that represents which value of the Fibonnaci sequence yo +u want to start with ie: 1 would be 1, and 2 would be 1, and 3 would be 2 and so on. Your choice: 90 Now pick a number to repesent the range you want. If you want to use values 1 through 10 you you need only enter 10, assuming of course you entered 1 above. Your choice: 10 2880067194370816120 / 1779979416004714189 = 1.618033988749894848204586 +834365638117579 4660046610375530309 / 2880067194370816120 = 1.618033988749894848204586 +834365638117774 7540113804746346429 / 4660046610375530309 = 1.618033988749894848204586 +8343656381177 12200160415121876738 / 7540113804746346429 = 1.61803398874989484820458 +6834365638117728 19740274219868223167 / 12200160415121876738 = 1.6180339887498948482045 +86834365638117717 31940434634990099905 / 19740274219868223167 = 1.6180339887498948482045 +86834365638117721 51680708854858323072 / 31940434634990099905 = 1.6180339887498948482045 +8683436563811772 83621143489848422977 / 51680708854858323072 = 1.6180339887498948482045 +8683436563811772 135301852344706746049 / 83621143489848422977 = 1.618033988749894848204 +58683436563811772 218922995834555169026 / 135301852344706746049 = 1.61803398874989484820 +458683436563811772 354224848179261915075 / 218922995834555169026 = 1.61803398874989484820 +458683436563811772 [download] You might have noticed the use of bignum btw. True laziness is hard work	[reply] [d/l] [select]
Re^3: how to speed up program dealing with large numbers? by Solarplight (Sexton) on Mar 23, 2010 at 09:31 UTC
thank you for the tips, one question though I don't quite understand this line: `my $phiApprox = $fibNum <= 1 ? '*' : $fibValue1 / $fibValue2;` In paticular this part: `? '' :` Obviously it makes $phiApprox = '**' when $fibNum is <= 1, else it performs the arithmatic. But I don't really understand why, I would never have thought of that code.	[reply] [d/l] [select]
Re^4: how to speed up program dealing with large numbers? by GrandFather (Saint) on Mar 23, 2010 at 09:50 UTC
$phiApprox is not defined in that case so rather than invent an number for it to be I used *** to indicate an unknown value. True laziness is hard work	[reply]