#119 - Initialize Stopwatch on constructor to allow resuming algorith…

…ms using a population that is not in the first generation (#120)

Co-authored-by: elpht <[email protected]>

src/GeneticSharp.Domain.UnitTests/GeneticAlgorithmTest.cs

@@ -858,6 +858,42 @@ public void Resume_TerminationReachedAndTerminationExtend_Resumed()
             Assert.AreEqual(GeneticAlgorithmState.TerminationReached, target.State);
             Assert.IsFalse(target.IsRunning);
         }
+
+        [Test]
+        public void Resume_PopulationFromAnotherGeneticAlgorithm_Resumed()
+        {
+            // Arrange
+            var selection = new EliteSelection();
+            var crossover = new OnePointCrossover(2);
+            var mutation = new UniformMutation();
+            var chromosome = new ChromosomeStub();
+            var population = new Population(100, 199, chromosome)
+            {
+                GenerationStrategy = new TrackingGenerationStrategy()
+            };
+            var fitnessStub = new FitnessStub { SupportsParallel = false };
+
+            // initialize a GA and run it for 100 generations
+            var initialGeneticAlgorithm = new GeneticAlgorithm(population, fitnessStub, selection, crossover, mutation)
+            {
+                Termination = new GenerationNumberTermination(100)
+            };
+            initialGeneticAlgorithm.Start();
+
+            // initialize a new GA with the same population to run it for 100 generations more
+            var target = new GeneticAlgorithm(population, fitnessStub, selection, crossover, mutation)
+            {
+                Termination = new GenerationNumberTermination(200)
+            };
+
+            // Act
+            target.Resume();
+
+            // Assert
+            Assert.AreEqual(200, target.Population.Generations.Count);
+            Assert.AreEqual(GeneticAlgorithmState.TerminationReached, target.State);
+            Assert.IsFalse(target.IsRunning);
+        }
 
     }
 }

src/GeneticSharp.Domain/GeneticAlgorithm.cs

@@ -68,7 +68,7 @@ public sealed class GeneticAlgorithm : IGeneticAlgorithm
         private bool m_stopRequested;
         private readonly object m_lock = new object();
         private GeneticAlgorithmState m_state;
-        private Stopwatch m_stopwatch;
+        private readonly Stopwatch m_stopwatch = new Stopwatch();
         #endregion              
 
         #region Constructors
@@ -258,7 +258,7 @@ public void Start()
             lock (m_lock)
             {
                 State = GeneticAlgorithmState.Started;
-                m_stopwatch = Stopwatch.StartNew();
+                m_stopwatch.Restart();
                 Population.CreateInitialGeneration();
                 m_stopwatch.Stop();
                 TimeEvolving = m_stopwatch.Elapsed;