HI Carl,<br> <br> First off thanks very much for the reply. Looks like I'm really getting my omoney's worth with that IPOPT support contract. ;)<br><br>I've actually already set >>option ipopt_options "halt_on_ampl_error=yes"<< and the output below includes this. Doesn't provide any elcuidation unfortunately. Still your point about --enable-doscompile under cygwin is very well-taken and I will certainly get on that tomorrow as the next step.<br> <br>My objective function includes a sum of logs but all variables are (in theory at least) well-bounded. What seems suspect are that 1) the problem solves in MINOS, and 2) the difficulty only starts occurring at right about the 100 variable level.<br><br>And again, I thank you very much for your help.<br>Jac.<br><br><b><i><br>Carl Laird <carl.d.laird@gmail.com></i></b> wrote:<blockquote class="replbq" style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;">This type of error happens
when there is a numerical evaluation<br>problem in AMPL (i.e. a constraint evaluates to infinity or NaN, sqrt<br>of a negative number, etc). You can add the following option to the<br>AMPL .mod file<br><br> option ipopt_options "halt_on_ampl_error=yes"<br><br><br>before the solve call. This will instruct AMPL to halt when it detects<br>an evaluation error and give some more details about the problem. It<br>looks like Ipopt is complaining about an infinite value coming from<br>the objective function evaluation, and setting the above option should<br>give more detailed information. The halt_on_ampl_error option is<br>particularily useful when the problem is with a constraint since it<br>causes AMPL to indicate which constraint was at fault.<br><br>This type of error typically happens to me when I have expressions<br>like exp(x) in my functions and I haven't limited x in any way.<br>Depending on the problem, x could become very large as it iterates and<br>cause an
evaluation error.<br><br>One final comment. When I compile in CYGWIN, I have to configure ipopt<br>with the --enable-doscompile option otherwise I have problems reading<br>options from AMPL. So, before you try the halt_on_ampl_error option,<br>make sure you configure with this option.<br><br>Hope this helps,<br><br>Carl.<br><br><br>On 4/12/07, Jacob C. <jacobcdf@yahoo.com> wrote:<br>> Running 3.2.3 on XP compiled with default under cygwin through AMPL.<br>><br>> It seems that when I hit roughly 100 variables IPOPT spits out the following<br>> (halt_on_ampl_error set to TRUE):<br>><br>> EXIT: Invalid number in NLP function or derivative detected.<br>> Error in an AMPL evaluation. Run with "halt_on_ampl_error yes" to see<br>> details.<br>> Exception of type: Eval_Error in file "IpOrigIpoptNLP.cpp" at line 403:<br>> Exception message: success && IsFiniteNumber(ret) evaluated false: Error<br>> evaluating the objective
function<br>><br>> EXIT: Some uncaught Ipopt exception encountered.<br>> can't open at1564.sol<br>><br>> -----------------------------<br>><br>> I'm very much a beginner and have little where to even start tracking this<br>> down. FWIW, the problem runs smoothly with MINOS 5.5. Will provide the model<br>> upon request.<br>><br>><br>> Thanks,<br>> Jac.<br>><br>><br>> ________________________________<br>> Don't get soaked. Take a quick peak at the forecast<br>> with theYahoo! Search weather shortcut.<br>><br>><br>> _______________________________________________<br>> Coin-ipopt mailing list<br>> Coin-ipopt@list.coin-or.org<br>> http://list.coin-or.org/mailman/listinfo/coin-ipopt<br>><br>><br></jacobcdf@yahoo.com></blockquote><br><p> 
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