Variable listing

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When GAMS generates the model by default the data for the first three cases in existence under each named variable will be generated.  A portion of the output (just that for the first two named variables) for the each for the three example models is

 

Column Listing    SOLVE farmPROBLEM Using LP From line 10

---- Z

Z

                (.LO, .L, .UP = -INF, 0, +INF)

        1       OBJ

---- Xcorn

Xcorn

                (.LO, .L, .UP = 0, 0, +INF)

     -109       OBJ

        1       land

        6       labor

 

Column Listing      SOLVE PROBLEM Using MCP From line 7

---- P

P

                (.LO, .L, .UP = 0, 0, +INF)

        1       PDemand

       -1       PSupply

---- Qd

Qd

                (.LO, .L, .UP = 0, 0, +INF)

        0.3     PDemand

       -1       Equilibrium

 

Column Listing    SOLVE wall Using NLP From line 28

---- ba

ba

                (.LO, .L, .UP = -INF, 1, +INF)

       (1)      r1

      (-1)      r2

        1       b1

        2       b2

---- so4

so4

                (.LO, .L, .UP = -INF, 1, +INF)

       (1)      r1

      (-1)      r3

       -1       b1

       -2       b2

Notes:

•The first part of this output gives the words Column Listing followed by the word Solve, the name of the model being solved and the line number in the echo print file where the solve associated with this model generation appears.
•The second part of this output consists of the marker ---- followed by the name of the variable.
•When one wishes to find this LST file component, one can search for the marker ---- or the string Column Listing.  Users will quickly find ---- marks other types of output like that from display statements.
•The third part of this output contains the variable name followed by (.LO, .L, .UP = lower bound, starting level, upper bound) where

lower bound gives the lower bound assigned to this variable (often zero)

starting level gives the starting point assigned to this variable (often zero)

upper bound gives the lower bound assigned to this variable (often positive infinity + INF).

•The fourth part of this output gives the equation names in which this variable appears with a nonzero term and the associated coefficients.
•The output is a correct representation of the algebraic structure of any linear terms in the equations where the variable appears and a local representation containing the first derivatives of any nonlinear terms.  The nonlinear terms are automatically encased in parentheses to indicate a local approximation is present just analogous to the portrayals in the equation listing section just above.

 More details on how the variable list is formed and controlled in terms of content and length are discussed in the Standard Output chapter while more on nonlinear terms appears in the NLP and MCP Model Types chapter.