Detect infeasibility

octachrome · Jul 21, 2014 · 31cbe25 · 31cbe25
1 parent 32a95f7
commit 31cbe25
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Showing 2 changed files with 20 additions and 1 deletion.
diff --git a/js/simplex.js b/js/simplex.js
@@ -101,7 +101,7 @@ function firstInfeasibility(mat) {
         }
 
         if (col === null) {
-            throw new Error('Failed to find a suitable pivot var for infeasible row ' + row);
+            return 'infeasible';
         }
         return {
             row: row,
@@ -231,6 +231,10 @@ function solve(mat, debug) {
             mat.status = 'optimal';
             break;
         }
+        if (pv === 'infeasible') {
+            mat.status = 'infeasible';
+            break;
+        }
         var pr = pivotRow(mat, pv);
         if (debug) {
             console.log(pr);

diff --git a/test/simplexSpec.js b/test/simplexSpec.js
@@ -379,6 +379,21 @@ describe('simplex', function () {
             expect(finalMat.status).toBe('unbounded');
         });
 
+        it('should detect an infeasible problem', function () {
+            var prob = readLp(
+                "maximise x\n\
+                subject to\n\
+                x <= 10\n\
+                x >= 20\n\
+                end\n"
+            );
+
+            var mat = toMatrix(prob);
+            var finalMat = solve(mat, true);
+
+            expect(finalMat.status).toBe('infeasible');
+        });
+
         it('should solve a small MPS problem', function () {
             var prob = readMps("\
 NAME          T       \n\