Skip to content

STMTS_General

Jump to bottom
Filipe Brandão edited this page May 20, 2016 · 11 revisions

General PyMPL Statements

EVAL

Usage: ${python expression}$

Description: is replaced by the result of eval("python expression").

Parameters:

  • Python:
    • valid python expression.

Creates:

  • AMPL:
    • is replaced by the result of evaluating the expression.

Examples:

...
var x1, >= ${2+6}$, <= ${10*5}$;
s.t. con1: x + y <= ${abs((2**7)/5-135)}$ * z;
...

is replaced by:

...
var x1, >= 8, <= 50;
s.t. con1: x + y <= 110 * z;
...

EXEC

Usage: $EXEC{python code};

Description: executes python code.

Parameters:

  • Python:
    • valid python code.

Creates:

  • AMPL:
    • May create anything that results from calls to PyMPL commands.
  • Python:
    • May create new python variables/functions/etc. that can be used in the following statements.

Examples:

...
$EXEC{
for i in range(3):
    STMT("var x{0}, integer, >= 0, <= {1};".format(i, i+1))
};
...

is replaced by:

var x0, integer, >= 0, <= 1;
var x1, integer, >= 0, <= 2;
var x2, integer, >= 0, <= 3;

Note: you call use PyMPL commands inside python code as follows:

  • $CMD[...]{...}; are equivalent to CMD["..."](...) in python code;
  • $CMD{...}; are equivalent to CMD(...) in python code.

STMT

Usage: $STMT{python expression};

Description: is replaced by the result of eval("python expression").

Parameters:

  • Python:
    • valid python expression.

Creates:

  • AMPL:
    • is replaced by the result of evaluating the expression.

Examples:

...
$STMT{"s.t. con1: x + y <= {0} * z;".format(abs((2**7)/5-135))};
$EXEC{stmt = "s.t. {0}: x >= 10;".format("test")};
$STMT{stmt};
...

is replaced by:

...
s.t. con1: x + y <= 110 * z;
s.t. test: x >= 10;
...

Note: $STMT{expression}; is equivalent to ${expression}$ (EVAL).

SET

Usage: $SET[set_name]{values};

Description: creates an AMPL sets.

Parameters:

  • AMPL:
    • 'set_name': set name.
  • Python:
    • values: list of values.

Creates:

  • AMPL:
    • a set named 'set_name'.
  • Python:
    • _set['set_name']: list of values.

Examples:

...
$SET[A]{range(5)};
$SET[B]{zip(range(5),range(5))};
...

is replaced by:

set A := {0,1,2,3,4};
set B := {(0,0),(1,1),(2,2),(3,3),(4,4)};

Note: Is is possible to call external functions (i.e., $SET[X]{some_function(...)}) that return the set.

PARAM

Usage: $PARAM[param_name]{values, i0=0};

Description: creates AMPL parameters.

Parameters:

  • AMPL:
    • Option 1: 'param_name' -> parameter name;
    • Option 2: 'param_name{Index_name}' -> parameter name and index name.
  • Python:
    • values: dictionary of key:value pairs or a list of values;
    • i0: initial index if values is a list of values.

Creates:

  • AMPL:
    • a parameter named 'param_name'.
  • Python:
    • _param['param_name']: dictionary with the parameter data.

Examples:

...
$PARAM[NAME]{"name"}; 
$PARAM[VALUE]{10};
$PARAM[D{I}]{{'a': 1, 'b': 2}};
$PARAM[L0]{[1,2,3], i0=0};
$PARAM[L1]{[1,2,3], i0=1}; # `i0` is the initial index if `values` is a list
...

is replaced by:

param NAME := 'name';
param VALUE := 10;
param D := ['a']1['b']2;
set I := {'a','b'};
param L0 := [0]1[1]2[2]3;
param L1 := [1]1[2]2[3]3;

Note: Is is possible to call external functions (i.e., $PARAM[X]{some_function(...)}) that return the parameter.

VAR

Usage: $VAR[var_name]{typ="", lb=None, ub=None, index_set=None};

Description: creates AMPL variables.

Parameters:

  • AMPL:
    • Option 1: 'var_name' -> variable name;
    • Option 2: 'var_name{Iname}' -> variable name and index name (index_set must be provided).
  • Python:
    • typ: variable type (e.g., "integer");
    • lb: variable lower bound;
    • ub: variable upper bound;
    • index_set: index set for the variable.

Creates:

  • AMPL:
    • creates a variable named 'var_name'.

Examples:

...
$VAR[x]{"integer", 0, 10};
$VAR[y]{"binary"};
$VAR[z]{ub=abs((2**7)/5-135)};
$VAR[xs{I}]{"integer", index_set=range(3)};
...

is replaced by:

var x, integer, >= 0, <= 10;
var y, binary; 
var z, <= 110;
set I := {0,1,2};
var xs{I}, integer;

CON

Usage: $CON[constraint_name]{left, sign, right};

Description: creates AMPL constraints.

Parameters:

  • AMPL:
    • 'constraint_name': constraint name.
  • Python:
    • left: list of variable names, values, or pairs (variable name, coefficient);
    • sign: constraint type (">=", "=", "<=");
    • right: list of variable names, values, or pairs (variable name, coefficient).

Creates:

  • AMPL:
    • a constraint named 'constraint_name'.

Examples:

...
$CON[con1]{[("x1",5),("x2",15),("x3",10)],">=",20};
$CON[con2]{[("x1",5),("x2",15),-20],">=",("x3",-10)};
$CON[con3]{[("x1",5)],">=",[("x2",-15),("x3",-10),20]};
$CON[con4]{-20,">=",[("x1",-5),("x2",-15),("x3",-10)]};
$CON[con5]{-20,">=",[(-5, "x1"),("x2",-15),(-10, "x3")]};
$CON[con6]{[-20, "x1"],">=",[(-4, "x1"),("x2",-15),(-10, "x3")]};
$CON[con7]{"x1",">=",[(-4, "x1"),20,("x2",-15),(-10, "x3")]};
...

is replaced by:

s.t. con1: +5*x1+15*x2+10*x3 >= 20;
s.t. con2: +5*x1+15*x2+10*x3 >= 20;
s.t. con3: +5*x1+15*x2+10*x3 >= 20;
s.t. con4: +5*x1+15*x2+10*x3 >= 20;
s.t. con5: +5*x1+15*x2+10*x3 >= 20;
s.t. con6: +5*x1+15*x2+10*x3 >= 20;
s.t. con7: +5*x1+15*x2+10*x3 >= 20;

Note: all the original constraints are just different representations of the same constraint.

Copyright © 2015-2016 Filipe Brandão < [email protected] >. All rights reserved.

Clone this wiki locally