http://support.gams-software.com/ 2008-10-15T08:32:53-04:00 http://support.gams-software.com/ http://support.gams-software.com/lib/images/favicon.ico text/html 2008-10-15T08:17:43-04:00 support http://support.gams-software.com/doku.php?id=gams:get_an_ordered_set_from_a_set_which_is_not_ordered&rev=1224073063&do=diff Ord() only works on ordered sets. Sets with elements, which have been introduced earlier, may not be ordered. Below is an example, how to get an ordered set in such a situation. Note: The functions sameas, .pos, and .val will also work, if the set is not ordered. text/html 2008-10-15T08:17:02-04:00 support http://support.gams-software.com/doku.php?id=gams:error_set_used_in_ord_or_lag_is_not_ordered&rev=1224073022&do=diff The ordering properties of a set can depend on the data in the set, and not on use. I am attaching an example, with comments, that should make this clear. Note: The functions sameas, .pos, and .val will also work, if the set is not ordered. * $ontext * Here, the set 'big' is not ordered; this is because the * elements in it have already appeared (in the sets even and odd), * but appeared in the order 0, 2, 4, 1, 3, 5, * not 0, 1, 2, 3, 4, 5 * Thus you will get an error message with the code … text/html 2008-10-10T20:51:47-04:00 support http://support.gams-software.com/doku.php?id=solver:terminating_the_optimization_after_the_first_feasible_solution&rev=1223686307&do=diff Q: Which GAMS or Cplex option can I use to make the solver stop quickly once a feasible solution has been found? On the GAMS level you can set optcr and optca to large numbers. If the bound and the value are on opposite sides of zero, this might result in larger values than one for optcr. For setting optca large enough you need some idea about the range of objective values. In GAMS/CPLEX there is also an option called intsollim. Setting intsollim to 1 will terminate the optimization after t… text/html 2008-10-10T20:45:46-04:00 support http://support.gams-software.com/doku.php?id=solver:solver&rev=1223685946&do=diff General * How can I hook my own solver to GAMS? * Solver ignores the iterlim/reslim settings in my model * How do I automatically re-submit a model, which failed due to a solver license error? * How much Memory (RAM) does my GAMS Run require? * Model is unbounded / Model has an unbounded ray / Model Status 3 unbounded * Changing the default Solver * Intercepting a Solver Call * The Solver Option File * How do I interrupt a solver? * Solver option file not found (wrong file e… text/html 2008-10-07T10:25:24-04:00 support http://support.gams-software.com/doku.php?id=gams:obtain_the_analytical_derivatives_of_the_objective_function_and_the_constraints&rev=1223389524&do=diff How do I obtain the analytical derivatives of the objective function and the constraints? * Distribution 21.4 introduced suffixes for functions: * New suffixes Grad and Hess have been introduced to get exact point derivatives from any function. These function suffixes are mainly intended for future testing of functions and cannot be used in equations. * The first argument gives the position of the element of the Hessian or gradient element desired in the form i or i:j, where i is the … text/html 2008-10-01T08:41:59-04:00 support http://support.gams-software.com/doku.php?id=gams:the_sum_of_consecutive_four_elements_in_a_vector_should_be_less_than_10&rev=1222864919&do=diff Q: Say a vector A has ten values (decision variables) Objective: Maximize the sum of A. How do I model this constraint: The sum of consecutive four elements in the vector should be less than 10. You can use the lag and lead operator (chapter 13.4 in the GAMS User's Guide) as in the following example: text/html 2008-10-01T08:38:41-04:00 support http://support.gams-software.com/doku.php?id=gams:gams&rev=1222864721&do=diff Beta Release Notes How do I... * model that constraint: The sum of consecutive four elements in a vector should be less than 10? * get a list of the available solvers in GAMS? * formulate logical expressions in equations? * get the "Active Process" Window back? * model predecessor/successor relations? * enter GAMS command line options? * export all elements of parameter (including Zeros) from GAMS into Excel? * write only the binding constraints to an external file? * obtai… text/html 2008-10-01T08:32:53-04:00 support http://support.gams-software.com/doku.php?id=gams:get_a_list_of_the_available_solvers_in_gams&rev=1222864373&do=diff * Windows * IDE: File -> Options -> Solvers * Command line interface: Change to the GAMS system directory and run gamsinst * Unix: Change to the GAMS system directory and run gamsinst text/html 2008-09-30T23:17:19-04:00 support http://support.gams-software.com/doku.php?id=installation:how_do_i_install_the_gams_version_for_macintosh&rev=1222831039&do=diff Like the other UNIX versions, GAMS for Macintosh is a Mac OS X Terminal application and must be installed and executed using the command line interface. It does currently not have a graphical user interface like the version for Windows. In case you are not familiar with the usage of the Mac OS X terminal, please visit an online tutorial like this one. text/html 2008-09-26T06:43:53-04:00 support http://support.gams-software.com/doku.php?id=gams:call_gams_within_gams&rev=1222425833&do=diff There are various options to execute GAMS (or other programs) within GAMS: * during compilation: $call 'external program' * during execution: execute 'external program'; Note: $call 'external program' calls the shell to execute you command and shell commands like redirection (>) or piping (|) are possible. $call '=external program' calls a single executable without using the shell. In most cases you can use just $call 'external program', but is a slight overhead with the shell call.