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Re: NInegrate Bug

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116573] Re: NInegrate Bug
  • From: Alexey <lehin.p at gmail.com>
  • Date: Sun, 20 Feb 2011 05:26:10 -0500 (EST)
  • References: <ijispp$2dp$1@smc.vnet.net>

On 17 =D1=84=D0=B5=D0=B2, 15:20, "Kurt TeKolste" <tekol... at fastmail.net> wrote:
> Are the conditions under which the incorrect answer is returned known so
> that a practitioner can implement a workaround of the form
>
> fixedNintegrate[function_,bounds_]:=
> =C2  If[ conditions[function],
> =C2  NIntegrate[function[t]*Sign[t],bounds],NIntegrate[function[t],bounds]]
>
> and be confident that one's analysis is not scrogged?

At least in the case of NIntegrate[Sin[x^2], {x, -5, -2}] and similar
switching symbolic preprocessing off does the trick:

In[15]:= f[x_?NumericQ] := Sin[x^2]
NIntegrate[f[x], {x, -5, -2}]

Out[16]= -0.276859

In[6]:= NIntegrate[Sin[x^2], {x, -5, -2},
 Method -> {"SymbolicPreprocessing", "SymbolicProcessing" -> 0}]

Out[6]= -0.276859


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