add amplsolver to README

README.md

@@ -4,11 +4,12 @@
 
 This project is dedicated to the development of links between [GAMS](http://www.gams.com) (**G**eneral **A**lgebraic **M**odeling **S**ystem) and some solvers,
 including some of the [COIN-OR](https://www.coin-or.org) open source solvers.
-The links are written in C++ and are released as open source code under the Eclipse Public Licence (EPL) 2.0.
+The links are written in C/C++ and are released as open source code under the Eclipse Public Licence (EPL) 2.0.
 The COIN-OR project leader for GAMSlinks is [Stefan Vigerske](http://www.gams.com/~svigerske) (GAMS Software GmbH).
 
 Currently the following links are available:
 
+ * [AmplSolver]: Call a solver with AMPL interface (AMPL `.nl` and `.sol` files)
  * [Bonmin](https://github.com/coin-or/Bonmin): Basic Open-source Nonlinear Mixed-Integer Programming
  * [Couenne](https://github.com/coin-or/Couenne): Convex Over and Under Envelopes for Nonlinear Estimation
  * [Cbc](https://github.com/coin-or/Cbc): COIN-OR Branch and Cut code
@@ -88,6 +89,9 @@ Note, that entries in gamsconfig.yaml overwrite solvers with the same name that
 
 For more information we refer to the [GAMS documentation](http://www.gams.com/latest/docs).
 
+For solver `AMPLSOLVER`, the solver binary needs to be specified in a solver options file (e.g., `amplsolver.opt`).
+See the installed `<prefix>/share/doc/gamslinks/optamplsolver.md` for a list of all available options.
+
 ## Testing
 
 The directory `test` contains scripts that test Cbc, Ipopt, Bonmin, Couenne, OsiXyz, SoPlex, and SCIP on some models from the GAMS test and model libraries.

src/amplsolver/optamplsolver.cpp

@@ -15,7 +15,9 @@ int main(int argc, char** argv)
  // General parameters
  gmsopt.setGroup("General Options");
 
- gmsopt.collect("solver", "AMPL solver executable (name or full path)", "", "", -2);
+ gmsopt.collect("solver", "AMPL solver executable (name or full path)",
+ "This option needs to be specified always.",
+ "", -2);
 
  gmsopt.collect("solvername", "AMPL solver name",
  "The name of the solver as used when specifying solver options in AMPL script. "