Skip to main content
Cross Validated

Return to Answer

logorithm does not sound right
Source Link
Xi'an
Xi'an
  • 107.7k
  • 13
  • 190
  • 676

This is just quoting the article under the "Algorithm LG: (LogorithmLogarithm method)" section :

In FORTRAN the algorithm is best programmed directly as $X=-ALOG(REGOL(IR))$ avoiding any subprogram call. The performance was 504 $\mu$sec per sample. Of this time 361 $\mu$sec was taken up by the manufacturer's logarithm routine and 105 $\mu$sec by the generator for REGOL of the uniformly distributed variable $u$. Therefore there was no point in trying to improve speed by writing an assembler function which would have to use the same two subprograms.

So it looks like the authors opted for other methods to avoid this "manufacturer" limitation of slow logorithmslogarithms. Perhaps this question is then best moved to stackoverflow where someone with knowledge on the guts of R can comment.

This is just quoting the article under the "Algorithm LG: (Logorithm method)" section :

In FORTRAN the algorithm is best programmed directly as $X=-ALOG(REGOL(IR))$ avoiding any subprogram call. The performance was 504 $\mu$sec per sample. Of this time 361 $\mu$sec was taken up by the manufacturer's logarithm routine and 105 $\mu$sec by the generator for REGOL of the uniformly distributed variable $u$. Therefore there was no point in trying to improve speed by writing an assembler function which would have to use the same two subprograms.

So it looks like the authors opted for other methods to avoid this "manufacturer" limitation of slow logorithms. Perhaps this question is then best moved to stackoverflow where someone with knowledge on the guts of R can comment.

This is just quoting the article under the "Algorithm LG: (Logarithm method)" section :

In FORTRAN the algorithm is best programmed directly as $X=-ALOG(REGOL(IR))$ avoiding any subprogram call. The performance was 504 $\mu$sec per sample. Of this time 361 $\mu$sec was taken up by the manufacturer's logarithm routine and 105 $\mu$sec by the generator for REGOL of the uniformly distributed variable $u$. Therefore there was no point in trying to improve speed by writing an assembler function which would have to use the same two subprograms.

So it looks like the authors opted for other methods to avoid this "manufacturer" limitation of slow logarithms. Perhaps this question is then best moved to stackoverflow where someone with knowledge on the guts of R can comment.

Source Link
Alex R.
Alex R.
  • 14.1k
  • 4
  • 29
  • 51

This is just quoting the article under the "Algorithm LG: (Logorithm method)" section :

In FORTRAN the algorithm is best programmed directly as $X=-ALOG(REGOL(IR))$ avoiding any subprogram call. The performance was 504 $\mu$sec per sample. Of this time 361 $\mu$sec was taken up by the manufacturer's logarithm routine and 105 $\mu$sec by the generator for REGOL of the uniformly distributed variable $u$. Therefore there was no point in trying to improve speed by writing an assembler function which would have to use the same two subprograms.

So it looks like the authors opted for other methods to avoid this "manufacturer" limitation of slow logorithms. Perhaps this question is then best moved to stackoverflow where someone with knowledge on the guts of R can comment.