intlinprog
Output Function and Plot Function Syntax
What Are Output Functions and Plot Functions?
intlinprog
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 branchandbound, appreciably
improving the relative gap, or exploring a number of nodes in a branchandbound
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 builtin 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 namedxIntSol
in your base workspace, where each column is one integer feasible point. It saves the objective function values in a vector namedfIntSol
, where each entry is the objective function of the corresponding column inxIntSol
.There is one builtin plot function:
optimplotmilp
. This function plots the internallycalculated bounds on the best objective function value. For an example of its use, see Factory, Warehouse, Sales Allocation Model: SolverBased.
Call output functions or plot functions by passing the OutputFcn
or
PlotFcn
namevalue arguments, 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});
Custom Function Syntax
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 totrue
to haltintlinprog
. Set tofalse
to allowintlinprog
to continue.x
— Either an empty matrix[]
or anN
by1
vector that is a feasible point.x
is nonempty only whenintlinprog
finds a new integer feasible solution.x
can be nonempty whenphase
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 builtin
functions savemilpsolutions.m
or optimplotmilp.m
.
optimValues
Structure
optimValues Field  Meaning 

dualbound  Global lower bound of the objective function value for minimization
problems, global upper bound for maximization problems. Empty when

fval  Best objective function found so far at an integer feasible point. When

numfeaspoints  Number of integer feasible solutions found that improve the current solution. 
numnodes  Number of explored nodes. Nonzero only when 
phase  Phase of the algorithm. For the

relativegap  Relative gap between

time  Time in seconds spent so far, measured with 