Re^2: Most Significant Set Bit

in reply to Re: Most Significant Set Bit
in thread Most Significant Set Bit

Unfortunately the log function isn't inexpensive

True, but you can halve the expense for large numbers of evaluations by storing log(2), which is just a constant.

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Comment on Re^2: Most Significant Set Bit

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Re^3: Most Significant Set Bit by Danny (Chaplain) on Mar 15, 2024 at 23:20 UTC
Strangely using a stored `$log2 = log(2)` in the above test did not improve the log function speed. It was actually slightly slower. EDIT: similar also with `use constant log2 => log(2)` EDIT2: The interpreter must compile such constant expressions into a constant before running.	[reply] [d/l] [select]
Re^4: Most Significant Set Bit by ikegami (Patriarch) on Mar 18, 2024 at 15:05 UTC
The interpreter must compile such constant expressions into a constant before running. Yes `$ perl -MO=Concise,-exec -e'my $x = log(2);' 1 <0> enter v 2 <;> nextstate(main 1 -e:1) v:{ 3 <$> const[NV 0.693147180559945] s/FOLD 4 <1> padsv_store[$x:1,2] vKS/LVINTRO 5 <@> leave[1 ref] vKP/REFC -e syntax OK` [download]	[reply] [d/l]

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