[Chicken-users] Nursery sizing considered stupid

[John Cowan]

A 15% improvement in efficiency, easily achieved, is certainly well
worth making.  Here's what nursery sizing showed me today under the
CMake build (the system was otherwise idle except for the usual transient
network events):

-- Determining the best stack size.
-- Running 10 samples per given stack size.
-- Requiring a 5% performance improvement to override the default stack size.
-- default stack size 131072 bytes -> 153.300 ms
-- stack size 16K -> 142.300 ms
-- stack size 24K -> 237.700 ms
-- stack size 32K -> 207.900 ms
-- stack size 48K -> 135.900 ms
-- stack size 64K -> 145.500 ms
-- stack size 128K -> 129.500 ms
-- stack size 256K -> 128.300 ms
-- stack size 512K -> 131.300 ms
-- stack size 1024K -> 125.200 ms
-- Using a stack size of 131072 bytes.
       It shows a 15% performance improvement over the default stack size.

Brilliant!  128K shows a 15% improvement over the default 128K!

There is something very, very wrong with all this.  IMNSHO, Chicken
should pick a stack size like 128K and stick to it; the measurement
procedure is so grossly unreliable that it's just as likely to choose
something seriously suboptimal.  People who actually need a different
value can use a configuration option or else -:s.

-- 
And it was said that ever after, if any                 John Cowan
man looked in that Stone, unless he had a               address@hidden
great strength of will to turn it to other              http://ccil.org/~cowan
purpose, he saw only two aged hands withering
in flame.   --"The Pyre of Denethor"