Re^2: Most Significant Set Bit

[hippo]

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.

[Danny]

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.

[ikegami]

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