Re: Possible simple bug in NMaximize

*To*: mathgroup at smc.vnet.net*Subject*: [mg71086] Re: [mg71040] Possible simple bug in NMaximize*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 8 Nov 2006 06:06:12 -0500 (EST)*References*: <200611060752.CAA08685@smc.vnet.net> <385666A3-8452-4267-9A16-51F52DC79904@mimuw.edu.pl>

On 6 Nov 2006, at 19:05, Andrzej Kozlowski wrote: > > On 6 Nov 2006, at 16:52, Nick Grishin wrote: > >> (* does not work *) >> func = Hold[NIntegrate[t^3, {t, x, 0}]]; >> NMaximize[func, x] >> >> (* works *) >> func = Hold[NIntegrate[t^3, {t, 0, x}]]; >> NMinimize[func, x] >> >> $Version >> 5.2 for Microsoft Windows (June 20, 2005) >> > > A bug in NMaximize? Why? It behaves exactly as it should do with > this kind of input. The problem is with MMinimize, because you > when you give it nonsensical input it actually produces output, > which unfortunately (by sheer accident), looks as if it might be > right. But it is nonssense nonetheless (nonsense in - > nonsense > out) nonsensical, and to convince you of it I will slightly change > your input: > > func = Hold[NIntegrate[t^3, {t, 10, x}]]; > > > NMinimize[func, x] > > > {-2500.0000000000005, {x -> -0.0002833987269403981}} > > Now, does this look like it "works"? > > Andrzej Kozlowski One correct way to do this kind of thing would be: func [x_?NumericQ] := NIntegrate[t^3, {t, 0, x}] Then Chop[NMinimize[func[x], x]] {0, {x -> -8.478781415049459*^-9}} and NMaximize[func[x], x] NMaximize::"cvdiv" : "Failed to converge to a solution. The function may be unbounded. {8.16355648507784698932167375`15.954589770191005*^537, {x -> -4.250938758824719*^134}} both of which at least make sense. Andrzej Kozlowski Tokyo, Japan

**References**:**Possible simple bug in NMaximize***From:*Nick Grishin <grishin@chop.swmed.edu>