AMPLException not caught in Java

Support
1

Hi all,

I am using the Java AMPL API [2.0.12]. If I call ampl.solve();, the following gets written into my JAVA IDE console:

com.ampl.AMPLException: presolve, constraint fix_value_1_4_to_1:
all variables eliminated, but lower bound = 1 > 0

I tried to surround the ampl.solve() with a try-catch to catch an AMPLException or anything throwable but JAVA does not catch the exception.

Am I doing something wrong or is this a bug?

THX M

1 Like
2

Hi @michael,

Thanks for reporting this issue. What is the operating system you are running the application on?

3

Fast responder :wink:

WIN11

4

Hi @fdabrandao

Anything new on this topic?

Greetings M

5

Hi @michael,

Sorry for the late reply. There seems to be some compiler optimization happening in Visual Studio (the Java API works on top of the C++ API) that is causing the exception to not be passed to Java. We were able to reproduce the issue and we are working on a fix.

1 Like
6

Hi @michael,

It turns out that the reason for the exception not being thrown is that the message is being classified as warning and not as an error. By default warnings are only displayed. A workaround while we are working on an update is:

ampl.solve();
if (!ampl.getValue("solve_result").equals("solved")) {
   // handle the error
}
1 Like
7

Hi @fdabrandao

thank you for your reply.

The if condition should look like

ampl.solve();
if (!ampl.getValue("solve_result").equals("solved")) {
  // handle the error
}

as in the code snippet you provided, Java always goes into the if condition. :wink:

Wish u all the best! M

1 Like