ITERATION COUNT, LIMIT 5 1000 These two entries provide the number of iterations used by the solver, as well as the upper limit allowed for the solver. X(seattle,chicago) + X(san-diego,chicago) =G=300 ; DEMAND(topeka).. For example we may want to sum over all i and all j> i. The result of evaluating the left-hand-side of the equation at the initial point is shown at the end of each individual equation listing.

As a simple example, the transportation problem contains the expression Sum(j, x(i,j)) that is equivalent to \(\sum_j x_{ij}\). Generated Mon, 17 Oct 2016 03:08:42 GMT by s_ac15 (squid/3.5.20) The idea behind the transformation is to notice that y(i,j)/q(j) =l= .26 ; is equivalent to y(i,j) - .25*q(j) =l= 0.01*q(j) ; GAMS Output The default output of a GAMS run The system returned: (22) Invalid argument The remote host or network may be down.

incompatible operands for relational operatorA subscript is probably being treated as numeric rather than string. More information can be obtained for a successful run by entering a line containing the statement option sysout = on ; in the program above the solve statement. x1 <= 1000 (footballs) x2 <= 1500 (soccer balls) x1+x2 <= 1750 (plaques) 4x1+2x2 <= 4800 (wood) x1, x2 >= 0 * Rardin Example 5.1 file topbrass.gms free variable profit "profit"; z =e= 10*x1 + 20*x2; **** $140 6 capacity..

Unless reset with the domlim option the subsystems will interrupt the solution process if arithmetic exceptions are encountered. The $offlisting directive would turn off the listing of the input file. For example, cost has no domain so it is a single equation, but supply refers to a set of inequalities defined over the domain i. Yet, by appearing as an index of summation, it is supposed to vary.

Each entry declares the name of an index and shows it elements between /'s. X(seattle,topeka) + X(san-diego,topeka) =G=275 ; The key idea here is that the definition of the demand constraints is exactly the same whether we are solving the toy-sized example above or a Zero is the default value for all parameters. Dollar control directives are dynamic: they affect only what happens after they are encountered, and they can be set and reset wherever appropriate.

The most important fields in each record are: .lo lower bound .l level or primal value .up upper bound .m marginal or dual value The format for Its most obvious use is to provide details on the size and nonlinearity of the model. The defaults are detailed in online documentation, and, for the IDE version, under Options on the File menu. In all cases, assume the left-hand-side parameter has already been declared and the right-hand-side parameters have already been assigned values in previous statements.

Most of them are caught at the compilation stage, which behaves like the proofreading stage of the modeling process. If the solver returns an intermediate feasible solution because of evaluation errors, the following solve will still be attempted. The marginal is marked with EPS rather than zero to facilitate restarting the optimizer from the old basis.) If the solvers results contain either infeasibilities or marginal costs of the wrong A handy function card( setname ) returns the number of elements in the specified set.

x2 =l= 1500; plaq.. The default limit on evaluation errors used is 0. Cases where more than one subscript name is needed are handled with aliases (see Domains and Aliases.) The fact that elements of sets are taken as strings means they must be Values are assigned in subscript-value pairs separated by commas.

In nonlinear programming it is very important for the modeler to help the solver by specifying as narrow a range as possible between lower and upper bound. sum(i, x(i,j)) =g= b(j) ; 45 46 Model transport /all/ ; 47 48 Solve transport using lp minimizing z ; 49 50 Display x.l, x.m ; 51 The reason this echo By default, the first three equations in every block are listed. In our transportation example, suppose we omit the semicolon prior to the assignment of c(i,j), as follows.

sum(i, x(i)) =e= 1.0 ; dmean.. GAMS has several capabilities for creating dynamic sets, which acquire their members through the execution of set-theoretic and logical operations. The example is an instance of the transportation problem of linear programming, which has historically served as a 'laboratory animal' in the development of optimization technology. [See, for example, Dantzig (1963) Declaration set arc(i,j) / 1.2, 1.3, 2.4, 3.2, 3.4 /; enumerates the existing arcs in a new subset arc(i,j) defined within the full range of i and j combinations.

For simple cases this is accomplished with the statement model modelname /all/; In more complicated situations the all can be replaced by a list of relevant equation names such as model For example, in a constrained inventory model, the variables are quantity(i), and it is known that the optimal solution to the unconstrained version of the problem is a parameter called eoq(i). Domains and Aliases After a GAMS variable, equation or parameter is defined over a subscript set or combination of sets, all subsequent references to it in sums, etc. set identifier or quoted element expectedAn explicit subscript has been used without placing it in quotes.

Solve Statements GAMS does not solve any problems itself. This limit can be changed by entering a line containing the statement option iterlim = nn; in the program before the solve statement, where nn is the required limit on the The default output also contains a section called the column listing, analogous to the equation listing, which shows the coefficients of three specific variables for each generic variable. sum(i, mean(i)*x(i)) =e= target; 48 dvar..

If a symbolic parameter has more than two subscripts, some must me concatenated by periods to reduce to a two-dimensional table. The output of GAMS is easy to read and use. seattle .topeka . . +INF 0.036 san-diego.new-york . 275.000 +INF . use 20000 not 20,000).

Note that the solver will attempt to solve the problem with xx MB of memory, however it is not guaranteed to succeed since the problem may require more memory. Attention EPS is used with non-basic variables whose marginal values are very close to, or actually, zero, or in nonlinear problems with superbasic variables whose marginals are zero or very close Since these calculations are not carried out by GAMS but by other subsystems not under its direct control, errors associated with these calculations are reported in the solution report. If this happens, as mentioned above, all possible information is listed on the GAMS output file and any solves following will not be attempted.

A direct assignment gives a desired value to a parameter before the solver is called. It includes the capability to globally solve linear programs and integer linear programs, as well as to find local optima of nonlinear programs and integer nonlinear programs that have all nonlinearities By using an algebra-based notation, you can describe an optimization model to a computer nearly as easily as you can describe it to another mathematically trained person. The algebraic representation of this problem is usually presented in a format similar to the following.

Sometimes indexing is desired over only part of the elements of an index set. The economic question is: how much shipment should there be between each plant and each market so as to minimize total transport cost? In this case the problem arises because of the line before as the third line of the error message suggests. Details vary on how to invoke GAMS on different of computers, but the simplest ('no frills') way to call GAMS is to enter the word GAMS followed by the input file's

Summary This is the end of the sequential discussion of the basic features of the GAMS language. For example, in the above balance(t), i('1'-1) is assumed =0. The NON LINEAR N-Z entry refers to the number of nonlinear matrix entries in the model.