On 09/11/2014 03:36 PM, Fabien COELHO wrote:
Now that I've finished the detour and committed and backpatched the changes
to the way latency is calculated, we can get back to this patch. It needs to
Before rebasing, I think that there are a few small problems with the
modification applied to switch from an integer range to double.
(1) ISTM that the + 0.5 which remains in the PoissonRand computation comes
from the previous integer approach and is not needed here. If I'm not
mistaken the formula should be plain:
-log(uniform) * center
No. The +0.5 is to round the result to the nearest integer, instead of
truncating it down.
(2) I'm not sure of the name "center", I think that "lambda" or
"mean" would be more appropriate.
(shrug), I guess. The comment says that it's the value the average of a
series values is centered on, so "center" doesn't seem too bad. I guess
the mathematically accurate term would be "expected value".
(3) I wish that the maximum implied multiplier could be explicitely
documented in the source code. From pg_rand48 source code, I think
that it is 33.27106466687737
Oh, ok. That's an even smaller multiplier than I got just by feeding
DBL_MIN to the formula. I don't think that's worth worrying about. That
might change if the implementation of pg_erand48() is changed, so I'm a
bit reluctant to state it explicitly.
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