math lib change in OS X bug + workaround

*To*: mathgroup at smc.vnet.net*Subject*: [mg108833] math lib change in OS X bug + workaround*From*: Paul Makepeace <paulm at paulm.com>*Date*: Fri, 2 Apr 2010 05:21:25 -0500 (EST)

(Not sure if this has already been posted; sorry if this is old news.) I recently noticed FixedPointList[Cos, .7] does not complete with 7.0.1 on OS X 10.6.3 -- symptoms are Mathematica is stuck "Running...". After some digging it turns out it's oscillating indefinitely. Here's my edited exchange with WRI support: --- If I put a limit on the invocation it returns, then "Raw Form" shows the numbers are oscillating, presumably related to some precision issue. FixedPointList[Cos, .7, 500] 0.7390851332151605, 0.7390851332151608, 0.7390851332151605, 0.7390851332151608, 0.7390851332151605 --- WRI support replied, Hello, Thank you for the email. First I think is kernel problem. But it turned out it is not. I can reproduce this problem on my Mac machine. And I have consulted this problem with our development group. This is caused by the recent change of math library of OSX. The workaround might be specifying SameTest function, see below: In[1]:= FixedPointList[Cos, .7, SameTest -> (Equal[N[#1], N[#2]] &)] Out[1]= {0.7, 0.764842, 0.721492, 0.750821, 0.731129, 0.744421, \ 0.73548, 0.741509, 0.73745, 0.740185, 0.738344, 0.739584, 0.738749, \ 0.739312, 0.738932, 0.739188, 0.739016, 0.739132, 0.739054, 0.739106, \ 0.739071, 0.739095, 0.739079, 0.739089, 0.739082, 0.739087, 0.739084, \ 0.739086, 0.739085, 0.739086, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, 0.739085, \ 0.739085} I have forwarded your examples to our development group and have included your contact information so that you can be notified when this has been resolved. --- HTH, Paul