The LP Procedure 
This is an example of the Infeasible Information Summary that is displayed when an infeasible problem is encountered. Consider the following problem:
Examination of this problem reveals that it is unsolvable. Consequently, PROC LP identifies it as infeasible. The following program attempts to solve it.
data infeas; format _id_ $6.; input _id_ $ x1x4 _type_ $ _rhs_; datalines; profit 1 1 1 1 max . const1 1 3 2 4 le 5 const2 3 1 2 1 le 4 const3 5 3 3 3 eq 9 ;
The results are shown in Output 5.9.1.
Problem Summary  

Objective Function  Max profit 
Rhs Variable  _rhs_ 
Type Variable  _type_ 
Problem Density (%)  77.78 
Variables  Number 
Nonnegative  4 
Slack  2 
Total  6 
Constraints  Number 
LE  2 
EQ  1 
Objective  1 
Total  4 
ERROR: Infeasible problem. Note the constraints in the constraint summary that are identified as infeasible. If none of the constraints are flagged then check the implicit bounds on the variables.
Solution Summary  

Infeasible Problem 

Objective Value  2.5 
Phase 1 Iterations  2 
Phase 2 Iterations  0 
Phase 3 Iterations  0 
Integer Iterations  0 
Integer Solutions  0 
Initial Basic Feasible Variables  5 
Time Used (seconds)  0 
Number of Inversions  2 
Epsilon  1E8 
Infinity  1.797693E308 
Maximum Phase 1 Iterations  100 
Maximum Phase 2 Iterations  100 
Maximum Phase 3 Iterations  99999999 
Maximum Integer Iterations  100 
Time Limit (seconds)  120 
Variable Summary  

Col  Variable Name  Status  Type  Price  Activity  Reduced Cost 
1  x1  BASIC  NONNEG  1  0.75  0 
2  x2  BASIC  NONNEG  1  1.75  0 
3  x3  NONNEG  1  0  0.5  
4  x4  NONNEG  1  0  0  
*INF*  const1  BASIC  SLACK  0  1  0 
6  const2  SLACK  0  0  0.5 
Constraint Summary  

Row  Constraint Name 
Type  S/S Col  Rhs  Activity  Dual Activity 
1  profit  OBJECTVE  .  0  2.5  . 
*INF*  const1  LE  5  5  6  0 
3  const2  LE  6  4  4  0.5 
4  const3  EQ  .  9  9  0.5 
Infeasible Information Summary  

Infeasible Row  const1 
Constraint Activity  6 
Row Type  LE 
Rhs Data  5 
Variable  Coefficient  Activity  Lower Bound  Upper Bound 

x1  1  0.75  0  INFINITY 
x2  3  1.75  0  INFINITY 
x3  2  0  0  INFINITY 
x4  4  0  0  INFINITY 
Note the information given in the Infeasible Information Summary for the infeasible row CONST1. It shows that the inequality row CONST1 with righthand side 5 was found to be infeasible with activity 6. The summary also shows each variable that has a nonzero coefficient in that row and its activity level at the infeasibility. Examination of these model parameters might give you a clue as to the cause of infeasibility, such as an incorrectly entered coefficient or righthandside value.
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