The INTPOINT Procedure

Macro Variable _ORINTPO

The INTPOINT procedure creates and initializes a SAS macro variable called _ORINTPO. After exiting the procedure, you can use %put &_ORINTPO; to view details about the optimization.

The value of _ORINTPO consists of the following:

• ERROR_STATUS, indicating the existence or absence of any errors
• OPT_STATUS, the stage of the optimization, or what solution has been found
• OBJECTIVE=objective, the total cost or profit of the current solution. OBJECTIVE can be followed by or replaced by one of the following:
  • MAXFLOW=maxflow, the amount of the current solution's maximal flow, follows OBJECTIVE= if PROC INTPOINT is solving a maximal flow problem (MAXFLOW specified)
  • MINFLOW=minflow, the amount of the current solution's minimal flow, follows OBJECTIVE= if PROC INTPOINT is solving a minimal flow problem (MAXFLOW and MAXIMIZE specified at the same time)
  • SHORTEST_PATH=shortpath, the length of the shortest path, appears instead of OBJECTIVE= if PROC INTPOINT is solving a shortest path problem (SHORTPATH specified)
  • LONGEST_PATH=longpath, the length of the longest path, appears instead of OBJECTIVE= if PROC INTPOINT is solving a longest path problem (SHORTPATH and MAXIMIZE specified at the same time)
• SOLUTION, describing the nature of the current solution
• ITERATIONS=n, the number of iterations required to solve the problem
• ITERATING_TIME=Ti, the time in seconds taken by the interior point algorithm to perform iterations for solving the problem
• SOLUTION_TIME=Ts, the time in seconds taken by the procedure to presolve the problem, perform interior point iterations, and postsolve the problem

Nontrailing blank characters that are unnecessary are removed. Ideally, at the end a PROC INTPOINT run, _ORINTPO has the following value:

  
   ERROR_STATUS=OK OPT_STATUS=OPTIMAL OBJECTIVE=x 
   SOLUTION=OPTIMAL ITERATIONS=x ITERATING_TIME=x SOLUTION_TIME=x
 

If the preprocessor detects that a problem is infeasible, _ORINTPO has the following value:

  
   ERROR_STATUS=OK SOLUTION=INFEASIBLE 
   ITERATIONS=0 ITERATING_TIME=0 SOLUTION_TIME=0
 

Table 2.2 lists alternate values for the _ORINTPO value parts.

Table 2.2: PROC INTPOINT _ORINTPO Macro Values

Keyword	Value	Meaning
ERROR_STATUS	OK	no errors
	MEMORY	memory request failed
	IO	input/output error
	DATA	error in the data
	BUG	error in PROC INTPOINT
	SEMANTIC	semantic error
	SYNTAX	syntax error
	UNKNOWN	unknown error
OPT_STATUS	START	no optimization has been done
	STAGE_1	performing stage 1 optimization
	UNCON_OPT	reached unconstrained optimum, but there are side constraints
	STAGE_2	performing stage 2 optimization
	OPTIMAL	reached the optimum
OBJECTIVE	objective	total cost or profit
MINFLOW	minflow	if MAXFLOW and MAXIMIZE are specified at the same time
MAXFLOW	maxflow	if MAXFLOW is specified
SHORTEST_PATH	shortpath	if SHORTPATH is specified
LONGEST_PATH	longpath	if SHORTPATH and MAXIMIZE are specified at the same time
SOLUTION	NONOPTIMAL	more optimization is required
	STAGE_2_REQUIRED	reached unconstrained optimum, stage 2 optimization is required
	OPTIMAL	have determined the optimum
	INFEASIBLE	infeasible; no solution exists
	UNRESOLVED_OPTIMALITY _OR_FEASIBILITY	the optimization process stops before optimality or infeasibility can be proven
	MAXITERB_OPTION _STOPPED_OPTIMIZATION	the interior point algorithm stops after performing maximal number of iterations specified by the MAXITERB= option