intlinprog Output Function and Plot Function Syntaxintlinprog can call an output function
or plot function after certain events occur in the algorithm. These
events include completing a phase of the algorithm such as solving
the root LP problem, adding cuts, completing a heuristic successfully,
finding a new integer feasible solution during branch-and-bound, appreciably
improving the relative gap, or exploring a number of nodes in a branch-and-bound
tree.
Caution
intlinprog output functions and plot functions differ from those in other
solvers. For output functions or plot functions in other Optimization Toolbox™ solvers, see Output Function and Plot Function Syntax and Plot Functions.
There is one built-in output function: savemilpsolutions.
This function collects the integer feasible points that the algorithm
finds at event times. It puts the feasible points in a matrix named xIntSol in
your base workspace, where each column is one integer feasible point.
It saves the objective function values in a vector named fIntSol,
where each entry is the objective function of the corresponding column
in xIntSol.
There is one built-in plot function: optimplotmilp.
This function plots the internally-calculated bounds on the best objective
function value. For an example of its use, see Factory, Warehouse, Sales Allocation Model: Solver-Based.
Call output functions or plot functions by passing the OutputFcn or PlotFcn name-value
pairs, including the handle to the output function or plot function.
For example,
options = optimoptions(@intlinprog,'OutputFcn',@savemilpsolutions,'PlotFcn',@optimplotmilp); x = intlinprog(f,intcon,A,b,Aeq,beq,lb,ub,options);
If you have several output functions or plot functions, pass them as a cell array.
options = optimoptions(@intlinprog,'OutputFcn',{@savemilpsolutions,@customFcn});Write your own output function or plot function using this syntax:
function stop = customFcn(x,optimValues,state)intlinprog passes the data x, optimValues,
and state to your function.
stop — Set to true to
halt intlinprog. Set to false to
allow intlinprog to continue.
x — Either an empty matrix [] or
an N-by-1 vector that is a feasible
point. x is nonempty only when intlinprog finds
a new integer feasible solution. x can be nonempty
when phase is 'heuristics' or 'branching'.
optimValues — A structure
whose details are in optimValues Structure.
state — One of these values:
'init' — intlinprog is
starting. Use this state to set up any plots or data structures that
you need.
'iter' — intlinprog is
solving the problem. Access data related to the solver’s progress.
For example, plot or perform file operations.
'done' — intlinprog has
finished solving the problem. Close any files, finish annotating plots,
etc.
For examples of writing output or plot functions, see the built-in
functions savemilpsolutions.m or optimplotmilp.m.
optimValues StructureoptimValues Field | Meaning |
|---|---|
phase | Phase of the algorithm. Possible values:
|
fval | Best objective function found so far at an integer feasible
point. When |
lowerbound | Global lower bound of the objective function value. Empty
when |
relativegap | Relative gap between |
numnodes | Number of explored nodes. Nonzero only when |
numfeaspoints | Number of integer feasible solutions found. |
time | Time in seconds spent so far, measured with |