[Octave-bug-tracker] [bug #53509] log1p: difference result in Octave and MATLAB.

[Michele Ginesi]

Follow-up Comment #1, bug #53509 (project octave):

I think this shouldn't be reported as a bug: the function log1p is used to
compute in a more stable way when x is small in module. In fact in Octave
log1p(x) is computed as log (1+x) when x < - 0.5 or x > 1:

>> log1p(2.1) == log(3.1)
ans = 1
>> log1p(2) == log(3)
ans = 0

Probably Matlab simply uses a different threshold to decide when use the
definition log1p(x)==log(1+x) and when an alternative expansion:

>> log1p(0.3) == log(1.3)

ans =

  logical

   1

>> log1p(0.2) == log(1.2)

ans =

  logical

   0

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