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Out of memory with simple calc?

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1

I'm getting out of memory with a very simple calc.

I'm try to calc ow many topologies a binary tree might has given a number n of samples

So I simple try perl -E 'sub fac my ($n) = @_; $n == 1 ? 1 : $n * fac($n -1) sub top my ($n) = @_; $t = fac(2 * $n - 5) / (2 ** ($n - 3) * fac($n - 3) ) say top(3)'
Also, a other version of same math:

#!/usr/bin/env perl

use warnings;
use strict;
#use features;

sub factorial
 my ($n) = @_;
 $n == 1 ? 1 : $n * factorial($n -1)


sub topologies
 my ($n) = @_;
 my $a = (2 * $n) - 5;
 my $a_f = factorial($a);
 my $b = $n -3;
 my $b_f = factorial($b);
 my $c = 2 ** $b;
 my $q = $c * $b_f;
 my $t = $a_f / $q;
 return $t;


print "Enter number of taxas: ";
my $input = <STDIN>;
my $ntop = topologies();

print $ntop, "n";

And when I try even for a sample size 3. I got out of memory in a computer with 4GB of ram and 4GB of cache. The same to a 128GB or ram server.

I do not need this calc, I was just try for fun.
But I cannot figure out why I'm getting this out of memory message.

EDIT: I just get it when the sample is equal or smaller than 3

perl

share|improve this question

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Hint: what happens when $n <= 0 in the factorial sub?
  
  – mob
  Mar 26 at 19:45
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @mob actually is expected never have $n < 1 anyway if $n == 0 it will return 0, and of course follows the same logic of any mathematical operation. Decreasing to lower than 0 the result should away return 0. Anyway I understand that is better use $n <= 1 in sub fac routine. So: sub fac my ($n) = @_; $n <= 1 ? 1 : $n * fac($n -1)
  
  – Aureliano Guedes
  Mar 26 at 22:15
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Note: If you're using a 32-bit build of Perl, the maximum amount of memory the process can use is 2-3 GiB (depending on the OS), regardless of how much RAM the machine has.
  
  – ikegami
  Mar 27 at 0:06
  

  
  
  
  

add a comment | 

1

I'm getting out of memory with a very simple calc.

I'm try to calc ow many topologies a binary tree might has given a number n of samples

So I simple try perl -E 'sub fac my ($n) = @_; $n == 1 ? 1 : $n * fac($n -1) sub top my ($n) = @_; $t = fac(2 * $n - 5) / (2 ** ($n - 3) * fac($n - 3) ) say top(3)'
Also, a other version of same math:

#!/usr/bin/env perl

use warnings;
use strict;
#use features;

sub factorial
 my ($n) = @_;
 $n == 1 ? 1 : $n * factorial($n -1)


sub topologies
 my ($n) = @_;
 my $a = (2 * $n) - 5;
 my $a_f = factorial($a);
 my $b = $n -3;
 my $b_f = factorial($b);
 my $c = 2 ** $b;
 my $q = $c * $b_f;
 my $t = $a_f / $q;
 return $t;


print "Enter number of taxas: ";
my $input = <STDIN>;
my $ntop = topologies();

print $ntop, "n";

And when I try even for a sample size 3. I got out of memory in a computer with 4GB of ram and 4GB of cache. The same to a 128GB or ram server.

I do not need this calc, I was just try for fun.
But I cannot figure out why I'm getting this out of memory message.

EDIT: I just get it when the sample is equal or smaller than 3

perl

share|improve this question

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Hint: what happens when $n <= 0 in the factorial sub?
  
  – mob
  Mar 26 at 19:45
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @mob actually is expected never have $n < 1 anyway if $n == 0 it will return 0, and of course follows the same logic of any mathematical operation. Decreasing to lower than 0 the result should away return 0. Anyway I understand that is better use $n <= 1 in sub fac routine. So: sub fac my ($n) = @_; $n <= 1 ? 1 : $n * fac($n -1)
  
  – Aureliano Guedes
  Mar 26 at 22:15
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Note: If you're using a 32-bit build of Perl, the maximum amount of memory the process can use is 2-3 GiB (depending on the OS), regardless of how much RAM the machine has.
  
  – ikegami
  Mar 27 at 0:06
  

  
  
  
  

add a comment | 

I'm getting out of memory with a very simple calc.

I'm try to calc ow many topologies a binary tree might has given a number n of samples

So I simple try perl -E 'sub fac my ($n) = @_; $n == 1 ? 1 : $n * fac($n -1) sub top my ($n) = @_; $t = fac(2 * $n - 5) / (2 ** ($n - 3) * fac($n - 3) ) say top(3)'
Also, a other version of same math:

#!/usr/bin/env perl

use warnings;
use strict;
#use features;

sub factorial
 my ($n) = @_;
 $n == 1 ? 1 : $n * factorial($n -1)


sub topologies
 my ($n) = @_;
 my $a = (2 * $n) - 5;
 my $a_f = factorial($a);
 my $b = $n -3;
 my $b_f = factorial($b);
 my $c = 2 ** $b;
 my $q = $c * $b_f;
 my $t = $a_f / $q;
 return $t;


print "Enter number of taxas: ";
my $input = <STDIN>;
my $ntop = topologies();

print $ntop, "n";

And when I try even for a sample size 3. I got out of memory in a computer with 4GB of ram and 4GB of cache. The same to a 128GB or ram server.

I do not need this calc, I was just try for fun.
But I cannot figure out why I'm getting this out of memory message.

EDIT: I just get it when the sample is equal or smaller than 3

perl

share|improve this question

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

#!/usr/bin/env perl

use warnings;
use strict;
#use features;

sub factorial
 my ($n) = @_;
 $n == 1 ? 1 : $n * factorial($n -1)


sub topologies
 my ($n) = @_;
 my $a = (2 * $n) - 5;
 my $a_f = factorial($a);
 my $b = $n -3;
 my $b_f = factorial($b);
 my $c = 2 ** $b;
 my $q = $c * $b_f;
 my $t = $a_f / $q;
 return $t;


print "Enter number of taxas: ";
my $input = <STDIN>;
my $ntop = topologies();

print $ntop, "n";

share|improve this question

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

share|improve this question

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

asked Mar 26 at 19:38

Aureliano GuedesAureliano Guedes

1401313 bronze badges

1 Answer
1

active

oldest

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6

With $n = 3 your toplogies(3) will call factorial(1) and factorial(0). The latter one is improperly implemented and tries to create the factorial by calling factorial(-1) which then calls factorial(-2) which then calls factorial(-3) ..., i.e. an endless recursion where each step allocates more memory. This endless recursion will result therefore in the out of memory. Similar things happen with $n<3.

share|improve this answer

edited Mar 26 at 20:18

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. So it was bad implemented, better do sub fac my ($n) = @_; $n == 1 ? 1 : $n * fac($n -1).
  
  – Aureliano Guedes
  Mar 26 at 22:19
  

  
  
  
  

add a comment | 

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6

With $n = 3 your toplogies(3) will call factorial(1) and factorial(0). The latter one is improperly implemented and tries to create the factorial by calling factorial(-1) which then calls factorial(-2) which then calls factorial(-3) ..., i.e. an endless recursion where each step allocates more memory. This endless recursion will result therefore in the out of memory. Similar things happen with $n<3.

share|improve this answer

edited Mar 26 at 20:18

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. So it was bad implemented, better do sub fac my ($n) = @_; $n == 1 ? 1 : $n * fac($n -1).
  
  – Aureliano Guedes
  Mar 26 at 22:19
  

  
  
  
  

add a comment | 

6

With $n = 3 your toplogies(3) will call factorial(1) and factorial(0). The latter one is improperly implemented and tries to create the factorial by calling factorial(-1) which then calls factorial(-2) which then calls factorial(-3) ..., i.e. an endless recursion where each step allocates more memory. This endless recursion will result therefore in the out of memory. Similar things happen with $n<3.

share|improve this answer

edited Mar 26 at 20:18

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. So it was bad implemented, better do sub fac my ($n) = @_; $n == 1 ? 1 : $n * fac($n -1).
  
  – Aureliano Guedes
  Mar 26 at 22:19
  

  
  
  
  

add a comment | 

With $n = 3 your toplogies(3) will call factorial(1) and factorial(0). The latter one is improperly implemented and tries to create the factorial by calling factorial(-1) which then calls factorial(-2) which then calls factorial(-3) ..., i.e. an endless recursion where each step allocates more memory. This endless recursion will result therefore in the out of memory. Similar things happen with $n<3.

share|improve this answer

edited Mar 26 at 20:18

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges

share|improve this answer

edited Mar 26 at 20:18

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges

answered Mar 26 at 19:49

Steffen UllrichSteffen Ullrich

66.1k33 gold badges6767 silver badges109109 bronze badges