From ef60915aa9d88b314d68a7fb0c987437abb93953 Mon Sep 17 00:00:00 2001
From: Chris Brown <chris@thebrown.net>
Date: Mon, 21 Jul 2014 08:57:10 +0100
Subject: [PATCH] Detect unbounded problem

---
 js/simplex.js       | 14 ++++++++++----
 test/simplexSpec.js | 15 +++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/js/simplex.js b/js/simplex.js
index a799496..38e8a7b 100644
--- a/js/simplex.js
+++ b/js/simplex.js
@@ -224,18 +224,24 @@ function solve(mat, debug) {
         if (pv === null) {
             pv = pivotVar(mat);
         }
+        if (debug) {
+            console.log(pv);
+        }
         if (pv === null) {
             break;
         }
         var pr = pivotRow(mat, pv);
-        if (pr === null) {
-            break;
-        }
         if (debug) {
-            console.log(pv);
             console.log(pr);
         }
+        if (pr === null) {
+            mat.status = 'unbounded';
+            break;
+        }
         mat = pivot(mat, pr, pv.col);
     }
+    if (!mat.status) {
+        mat.status = 'optimal';
+    }
     return mat;
 }
diff --git a/test/simplexSpec.js b/test/simplexSpec.js
index e39e96c..bd722f3 100644
--- a/test/simplexSpec.js
+++ b/test/simplexSpec.js
@@ -364,6 +364,21 @@ describe('simplex', function () {
             expect(sol._obj).toBeCloseTo(200);
         });
 
+        iit('should detect an unbouned problem', function () {
+            var prob = readLp(
+                "maximise\n\
+                3x - 2y\n\
+                subject to\n\
+                y <= 100\n\
+                end\n"
+            );
+
+            var mat = toMatrix(prob);
+            var finalMat = solve(mat);
+
+            expect(finalMat.status).toBe('unbounded');
+        });
+
         it('should solve a small MPS problem', function () {
             var prob = readMps("\
 NAME          T       \n\