Performance of tables slower than built in?

Ola Fosheim Grøstad ola.fosheim.grostad at gmail.com
Thu May 23 22:03:21 UTC 2019


On Thursday, 23 May 2019 at 21:50:38 UTC, Alex wrote:
> I've used very small LUT's like a length of 5 and it didn't 
> significantly change anything.

Use a size that is 2^n, then mask the index and hopefully that 
will turn off bounds checks.

E.g. If LUT size is 16, then index the lut with "i&15"?

> I haven't tested this well but was just thrown off by the 
> results as it should easily have been inverted and I expected 
> quite a significant speed up(several factors) and not the 
> reverse.

Well, you could take the time times clock frequency, divide it by 
number of iterations and calculate number of cycles per 
iteration. If it is more than a dozen, then something is wrong.




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