Re^2: reliable get position of leftmost bit in large integers

Works perfect. I only changed the testing-lines for better visability:

for (map 1 << $_, 0 .. 63) {
  print sprintf("%b", $_- 1 )," : ", sprintf("%b",nextPowerOfTwo( $_- 
+1 ));
}

$ perl leftmost_bit.pl 
0 : 0
1 : 1
11 : 100
111 : 1000
1111 : 10000
...
[download]

Maybe it's fast enough versus log(),division,log() if inlined. But I am only prototyping the pure Perl version for a C implementation. But it would be nice to have pure Perl as a fallback.

Comment on Re^2: reliable get position of leftmost bit in large integers Download Code

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Re^3: reliable get position of leftmost bit in large integers by BrowserUk (Patriarch) on Mar 12, 2015 at 13:13 UTC
I am only prototyping the pure Perl version for a C implementation. If your doing it in C, it is very efficient compared to other methods; and works well as an Inline::C routine. It originates from Bit Twiddling Hacks. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". I'm with torvalds on this In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked	[reply]
Re^4: reliable get position of leftmost bit in large integers by wollmers (Scribe) on Mar 12, 2015 at 14:54 UTC
I knew the Bit Twiddling page. But I hoped to get it shorter. Sure, pure C does not have the overhead. Helmut Wollmersdorfer	[reply]


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