Hash Function Speed Post: 302364241

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Top Forums Programming Hash Function Speed Post 302364241 by Corona688 on Thursday 22nd of October 2009 11:34:08 AM

10-22-2009

Registered User

Quote:

Originally Posted by jim mcnamara

It is missing { }, IMO.

Without { }, the loop will operate on the following statement instead of the following code block. If the loop had a semicolon on the end, then it would be truly pointless. Try the following code:

Code:

int n;
for(n=0; n<10; n++)
  printf("loop A %d\n", n);

for(n=0; n<10; n++);
  printf("loop B %d\n", n);

It looks to me like the intent was to only work on the following line -- why strip the value to table size every loop instead of just once -- so code blocks were left out. Better indenting would have showed the intent. For maximum clarity they could've surrounded the single line.

---------- Post updated at 09:34 AM ---------- Previous update was at 09:10 AM ----------

As for improving the hash function, there's not a lot to it as is. Slowdowns may be coming from other things. How full are your hash tables, how many collisions are you getting?

Last edited by Corona688; 10-22-2009 at 12:16 PM..

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tie::hash::namedcapture

Tie::Hash::NamedCapture(3pm)				 Perl Programmers Reference Guide			      Tie::Hash::NamedCapture(3pm)

NAME

       Tie::Hash::NamedCapture - Named regexp capture buffers

SYNOPSIS

	   tie my %hash, "Tie::Hash::NamedCapture";
	   # %hash now behaves like %+

	   tie my %hash, "Tie::Hash::NamedCapture", all => 1;
	   # %hash now access buffers from regexp in $qr like %-

DESCRIPTION

       This module is used to implement the special hashes "%+" and "%-", but it can be used to tie other variables as you choose.

       When the "all" parameter is provided, then the tied hash elements will be array refs listing the contents of each capture buffer whose name
       is the same as the associated hash key. If none of these buffers were involved in the match, the contents of that array ref will be as many
       "undef" values as there are capture buffers with that name. In other words, the tied hash will behave as "%-".

       When the "all" parameter is omitted or false, then the tied hash elements will be the contents of the leftmost defined buffer with the name
       of the associated hash key. In other words, the tied hash will behave as "%+".

       The keys of "%-"-like hashes correspond to all buffer names found in the regular expression; the keys of "%+"-like hashes list only the
       names of buffers that have captured (and that are thus associated to defined values).

SEE ALSO

       perlreapi, re, "Pragmatic Modules" in perlmodlib, "%+" in perlvar, "%-" in perlvar.

perl v5.16.2							    2012-10-11					      Tie::Hash::NamedCapture(3pm)