Example 6.4: An Infeasible Problem

The TRANS Procedure

Example 6.4: An Infeasible Problem

This example shows what happens when the total demand exceeds the total supply. The data from Example 6.1 are used with the demand at Atlanta increased to 100 units. Consequently, the demand exceeds the supply by 50 units. When the statements

   proc trans cost=cst;
      TAILNODE city;
      HEADNODE Atlanta--Washingt;
      supply supply;
   run;

are executed, the following message is written to the SAS log:

   ERROR: Infeasible network. Total supply 510 does not equal
          total demand 560.
          Use either the THRUNET or the NOTHRUNET option
          on the PROC TRANS statement.

However, if the THRUNET option is specified in the PROC TRANS statement, the procedure distributes the supply optimally among the source nodes. In that case, the statements

   title 'Using the THRUNET Option';

   proc trans data=cst THRUNET;
      TAILNODE city;
      HEADNODE Atlanta--Washingt;
      supply supply;
   run;

   proc print;
   run;

produce the following message on the SAS log and display the solution in Output 6.4.1.

   NOTE: Optimal Solution Total = 18302.

Output 6.4.1: Using the THRUNET Option

Using the THRUNET Option

Obs	city	supply	Atlanta	Chicago	Denver	Houston	Los_Ange	Miami	New_York	San_Fran	Seattle	Washingt	_DUAL_
1	_DEMAND_	.	50	75	89	8	27	39	64	100	50	8	.
2	Atlanta	10	10	0	0	0	0	0	0	0	0	0	-51
3	Chicago	150	30	75	2	0	0	0	0	0	43	0	-13
4	Denver	90	0	0	87	0	0	0	0	3	0	0	-85
5	Houston	27	0	0	0	8	19	0	0	0	0	0	-28
6	Los_Ange	80	0	0	0	0	8	0	0	72	0	0	-145
7	Miami	26	0	0	0	0	0	26	0	0	0	0	-89
8	New_York	80	0	0	0	0	0	8	64	0	0	8	0
9	San_Fran	25	0	0	0	0	0	0	0	25	0	0	-159
10	Seattle	7	0	0	0	0	0	0	0	0	7	0	-166
11	Washingt	15	10	0	0	0	0	5	0	0	0	0	-17
12	_DUAL_	.	71	33	105	48	165	109	20	179	186	20	.

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