Re: How does NIntegrate suppress messages?

*To*: mathgroup at smc.vnet.net*Subject*: [mg62614] Re: How does NIntegrate suppress messages?*From*: Andrew Moylan <andrew.moylan at anu.edu.au>*Date*: Tue, 29 Nov 2005 04:46:21 -0500 (EST)*References*: <dm95bd$6q1$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Excellent, thanks Ingolf. I think your post answers all the questions about this topic. Ingolf Dahl wrote: > Hi > A general method to suppress messages from Check is the following: > > Block[{$Messages = {}}, Check[expr, failexpr]] > > My theory is that Nintergrate uses the same mechanism. Can we find a way to > unsuppress the messages? > > One example: > > func[x_]:=1/x; > > x=0;Check[func[x],"Divide by zero"] > > gives both a message and evalutated failexpr, but > > x = 0; Block[{Set[$Messages, {}]}, Check[func[x], "Divide by zero"]] > > just evaluates failexpr. We might turn on the messages by redefining the > function: > > newfunc[x_] := Block[{Set[$Messages, {OutputStream["stdout", 1]}]}, > func[x]]; > > x = 0; Block[{Set[$Messages, {}]}, Check[newfunc[x], "Divide by zero"]] > > will give us the message back. To apply the same on NIntegrate is a bit > tricky.Define first > > f::err = "error"; f[x_?NumericQ] := ( Message[f::err]; x ) > > Then > > NIntegrate[f[x], {x, 0, 1}] > > will give no messages. Embedd f in a new function in the following ways: > > newf[ x_?NumericQ]:= ( Block[ { $MessageList=msl, $Messages= { > OutputStream[ "stdout",1]}}, { f[x], msl=$MessageList}[[1]]]) > > msl = {}; NIntegrate[newf[x], {x, 0, 1}] > > will then give you error messages. The NumericQ test is essential. > > Best regards > > Ingolf Dahl > Sweden > > > > >>-----Original Message----- >>From: Andrew Moylan [mailto:andrew.moylan at anu.edu.au] To: mathgroup at smc.vnet.net >>Sent: den 25 november 2005 08:25 >>Subject: [mg62614] Re: How does NIntegrate suppress messages? >> >>It's quite a mystery. My guess is that NIntegrate temporarily >>redefines the Message[...] function. >> >>Personally, I want to know because I want to copy this >>behaviour of NIntegrate for my own functions, if it is easy. >>Often I write code that uses Check, and I don't want the >>messages generated and appearing as errors and clogging up the output. >> >>"Alan" <info at optioncity.REMOVETHIS.net> wrote in message >>news:dm499k$srh$1 at smc.vnet.net... >> >>>"Andrew Moylan" <andrew.moylan at anu.edu.au> wrote in message >>>news:dm1b0v$ic1$1 at smc.vnet.net... >>> >>>>Whenever the integrand in NIntegrate generates messages >> >>(by calling >> >>>>Message), the output of these messages are suppressed, >> >>although they >> >>>>are still generated in the sense that they can be caught >> >>using Check. >> >>>>Does anyone know how NIntegrate does this? >>> >>>I don't, but your post answers a question of mine about >> >>behavior which >> >>>has always seemed a puzzle. Often I will wrap a complicated >>>computation in a Check in order to Abort[] on any message. Then, I >>>will sometimes get an Abort[], but no message! And, indeed, >> >>often an >> >>>NIntegrate is involved. When that occurs, I have never been able to >>>re-write the code to retrieve those missing messages. >>>So if there is a way to "unsuppress", that will be helpful >> >>to me, too. >> >>>regards, >>>alan >>> >>> >> >> >> > >