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niceperl (8613)
niceperl
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Saturday September 13, 2008
04:53 AM
fibonacci numbers
I wrote a small script in Perl to calc the N first terms of Fibonacci serie:
#-- fibo script
sub fibo {
return 1 if( $_[0] < 2 ) ;
return fibo($_[0]-1) + fibo($_[0]-2);
}
for($i=0; $i<=40; $i++) {
$f = fibo($i);
print "$i : $f\n";
}
#-- eof fibo.pl
I tried to calc the first 40 numbers, it tooks in my PC about 16 minutes. I weren't worried about writting a fast algoritm, just curious about the performance of a recursive call algorithm.
A friend of me, advertised me that the similar Java version code, ran fast, so I tried:
// Java fibonnaci class
class fibo {
public static long calc(long x) {
if( x < 2 ) return 1;
return calc(x-1) + calc(x-2);
}
public static void main(String s[]) {
for(int i=0; i<=40; i++) {
System.out.println(i + " : " + calc(i));
}
}
}
// EOF Java fibonnaci class
----------------------------
The results (40 terms calc):
1) Perl: 16 minutes
2) Java: 16 seconds (!)
I'm sure that Java does some kind of optimization at the Virtual Machine.
I hope that Parrot team will be able to make a very fast virtual machine...
#-- fibo script
sub fibo {
return 1 if( $_[0] < 2 )
return fibo($_[0]-1) + fibo($_[0]-2);
}
for($i=0; $i<=40; $i++) {
$f = fibo($i);
print "$i : $f\n";
}
#-- eof fibo.pl
I tried to calc the first 40 numbers, it tooks in my PC about 16 minutes. I weren't worried about writting a fast algoritm, just curious about the performance of a recursive call algorithm.
A friend of me, advertised me that the similar Java version code, ran fast, so I tried:
// Java fibonnaci class
class fibo {
public static long calc(long x) {
if( x < 2 ) return 1;
return calc(x-1) + calc(x-2);
}
public static void main(String s[]) {
for(int i=0; i<=40; i++) {
System.out.println(i + " : " + calc(i));
}
}
}
// EOF Java fibonnaci class
----------------------------
The results (40 terms calc):
1) Perl: 16 minutes
2) Java: 16 seconds (!)
I'm sure that Java does some kind of optimization at the Virtual Machine.
I hope that Parrot team will be able to make a very fast virtual machine...
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-- Jarkko Hietaniemi
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Memoize (Score:1)
Re: (Score:1)
Re: (Score:1)
No. It just has fundamentally different execution model.
Re: (Score:1)
Re: (Score:1)
Java will look for heavily used sections of code, aggressively optimize them, and rewrite in machine code. That is the reason for the performance difference.
O(2^n) (Score:1)
It's also the classic example (it's in SICP) of how a bad algorithm choice can get really slow really fast.