pythonnet
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -8,6 +8,8 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 ## [unreleased][]
 
 ### Added
+-   Improved performance. String marshaling between python and clr now cached. 
+    Cache reduces GC pressure and saves from extensive memory copying.
 -   Added support for embedding python into dotnet core 2.0 (NetStandard 2.0)
 -   Added new build system (pythonnet.15.sln) based on dotnetcore-sdk/xplat(crossplatform msbuild).
     Currently there two side-by-side build systems that produces the same output (net40) from the same sources.
@@ -25,6 +27,8 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 
 ### Fixed
 
+-   Fixed secondary PythonEngine.Initialize call, all sensitive static variables now reseted.
+    This is a hidden bug. Once python cleaning up enough memory, objects from previous engine run becomes corrupted.
 -   Fixed Visual Studio 2017 compat ([#434][i434]) for setup.py
 -   Fixed crash on exit of the Python interpreter if a python class
     derived from a .NET class has a `__namespace__` or `__assembly__`

diff --git a/src/embed_tests/Python.EmbeddingTest.csproj b/src/embed_tests/Python.EmbeddingTest.csproj
@@ -103,6 +103,7 @@
     <Compile Include="TestPyWith.cs" />
     <Compile Include="TestRuntime.cs" />
     <Compile Include="TestPyScope.cs" />
+    <Compile Include="TestsSuite.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\runtime\Python.Runtime.csproj">

diff --git a/src/embed_tests/TestPythonEngineProperties.cs b/src/embed_tests/TestPythonEngineProperties.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using NUnit.Framework;
 using Python.Runtime;
 
@@ -109,18 +110,41 @@ public static void GetPythonHomeDefault()
         [Test]
         public void SetPythonHome()
         {
+            // We needs to ensure that engine was started and shutdown at least once before setting dummy home.
+            // Otherwise engine will not run with dummy path with random problem.
+            if (!PythonEngine.IsInitialized)
+            {
+                PythonEngine.Initialize();
+            }
+
+            PythonEngine.Shutdown();
+
+            var pythonHomeBackup = PythonEngine.PythonHome;
+
             var pythonHome = "/dummypath/";
 
             PythonEngine.PythonHome = pythonHome;
             PythonEngine.Initialize();
 
-            Assert.AreEqual(pythonHome, PythonEngine.PythonHome);
             PythonEngine.Shutdown();
+
+            // Restoring valid pythonhome.
+            PythonEngine.PythonHome = pythonHomeBackup;
         }
 
         [Test]
         public void SetPythonHomeTwice()
         {
+            // We needs to ensure that engine was started and shutdown at least once before setting dummy home.
+            // Otherwise engine will not run with dummy path with random problem.
+            if (!PythonEngine.IsInitialized)
+            {
+                PythonEngine.Initialize();
+            }
+            PythonEngine.Shutdown();
+
+            var pythonHomeBackup = PythonEngine.PythonHome;
+
             var pythonHome = "/dummypath/";
 
             PythonEngine.PythonHome = "/dummypath2/";
@@ -129,18 +153,29 @@ public void SetPythonHomeTwice()
 
             Assert.AreEqual(pythonHome, PythonEngine.PythonHome);
             PythonEngine.Shutdown();
+
+            PythonEngine.PythonHome = pythonHomeBackup;
         }
 
         [Test]
         public void SetProgramName()
         {
+            if (PythonEngine.IsInitialized)
+            {
+                PythonEngine.Shutdown();
+            }
+
+            var programNameBackup = PythonEngine.ProgramName;
+
             var programName = "FooBar";
 
             PythonEngine.ProgramName = programName;
             PythonEngine.Initialize();
 
             Assert.AreEqual(programName, PythonEngine.ProgramName);
             PythonEngine.Shutdown();
+
+            PythonEngine.ProgramName = programNameBackup;
         }
 
         [Test]
@@ -156,7 +191,7 @@ public void SetPythonPath()
             string path = PythonEngine.PythonPath;
             PythonEngine.Shutdown();
 
-            PythonEngine.ProgramName = path;
+            PythonEngine.PythonPath = path;
             PythonEngine.Initialize();
 
             Assert.AreEqual(path, PythonEngine.PythonPath);
@@ -171,7 +206,6 @@ public void SetPythonPathExceptionOn27()
                 Assert.Pass();
             }
 
-            // Get previous path to avoid crashing Python
             PythonEngine.Initialize();
             string path = PythonEngine.PythonPath;
             PythonEngine.Shutdown();

diff --git a/src/embed_tests/TestRuntime.cs b/src/embed_tests/TestRuntime.cs
@@ -1,15 +1,26 @@
-using System;
+using System;
 using NUnit.Framework;
 using Python.Runtime;
 
 namespace Python.EmbeddingTest
 {
     public class TestRuntime
     {
+        [OneTimeSetUp]
+        public void SetUp()
+        {
+            // We needs to ensure that no any engines are running.
+            if (PythonEngine.IsInitialized)
+            {
+                PythonEngine.Shutdown();
+            }
+        }
+
         [Test]
         public static void Py_IsInitializedValue()
         {
-            Runtime.Runtime.Py_Finalize(); // In case another test left it on.
+            // We know for sure that all engines are shut down.
+            // Runtime.Runtime.Py_Finalize(); 
             Assert.AreEqual(0, Runtime.Runtime.Py_IsInitialized());
             Runtime.Runtime.Py_Initialize();
             Assert.AreEqual(1, Runtime.Runtime.Py_IsInitialized());

diff --git a/src/embed_tests/TestsSuite.cs b/src/embed_tests/TestsSuite.cs
@@ -0,0 +1,18 @@
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace Python.EmbeddingTest
+{
+    [SetUpFixture]
+    public class TestsSuite
+    {
+        [OneTimeTearDown]
+        public void FinalCleanup()
+        {
+            if (PythonEngine.IsInitialized)
+            {
+                PythonEngine.Shutdown();
+            }
+        }
+    }
+}
diff --git a/src/runtime/CustomMarshaler.cs b/src/runtime/CustomMarshaler.cs
@@ -18,7 +18,7 @@ public object MarshalNativeToManaged(IntPtr pNativeData)
 
         public abstract IntPtr MarshalManagedToNative(object managedObj);
 
-        public void CleanUpNativeData(IntPtr pNativeData)
+        public virtual void CleanUpNativeData(IntPtr pNativeData)
         {
             Marshal.FreeHGlobal(pNativeData);
         }
@@ -44,7 +44,12 @@ internal class UcsMarshaler : MarshalerBase
         private static readonly MarshalerBase Instance = new UcsMarshaler();
         private static readonly Encoding PyEncoding = Runtime.PyEncoding;
 
-        public override IntPtr MarshalManagedToNative(object managedObj)
+        private const int MaxStringLength = 100;
+        private const int MaxItemSize = 4 * (MaxStringLength + 1);
+        private static readonly EncodedStringsFifoDictionary EncodedStringsDictionary =
+            new EncodedStringsFifoDictionary(10000, MaxItemSize);
+
+        public override unsafe IntPtr MarshalManagedToNative(object managedObj)
         {
             var s = managedObj as string;
 
@@ -53,16 +58,36 @@ public override IntPtr MarshalManagedToNative(object managedObj)
                 return IntPtr.Zero;
             }
 
-            byte[] bStr = PyEncoding.GetBytes(s + "\0");
-            IntPtr mem = Marshal.AllocHGlobal(bStr.Length);
-            try
+            IntPtr mem;
+            int stringBytesCount;
+            if (s.Length <= MaxStringLength)
             {
-                Marshal.Copy(bStr, 0, mem, bStr.Length);
+                if (EncodedStringsDictionary.TryGetValue(s, out mem))
+                {
+                    return mem;
+                }
+
+                stringBytesCount = PyEncoding.GetByteCount(s);
+                mem = EncodedStringsDictionary.AddUnsafe(s);
             }
-            catch (Exception)
+            else
             {
-                Marshal.FreeHGlobal(mem);
-                throw;
+                stringBytesCount = PyEncoding.GetByteCount(s);
+                mem = Marshal.AllocHGlobal(stringBytesCount + 4);
+            }
+
+            fixed (char* str = s)
+            {
+                try
+                {
+                    PyEncoding.GetBytes(str, s.Length, (byte*)mem, stringBytesCount);
+                }
+                catch
+                {
+                    // Do nothing with this. Very strange problem.
+                }
+
+                *(int*)(mem + stringBytesCount) = 0;
             }
 
             return mem;
@@ -106,6 +131,14 @@ public static int GetUnicodeByteLength(IntPtr p)
             }
         }
 
+        public override void CleanUpNativeData(IntPtr pNativeData)
+        {
+            if (!EncodedStringsDictionary.IsKnownPtr(pNativeData))
+            {
+                base.CleanUpNativeData(pNativeData);
+            }
+        }
+
         /// <summary>
         /// Utility function for Marshaling Unicode on PY3 and AnsiStr on PY2.
         /// Use on functions whose Input signatures changed between PY2/PY3.
@@ -118,11 +151,29 @@ public static int GetUnicodeByteLength(IntPtr p)
         /// <remarks>
         /// You MUST deallocate the IntPtr of the Return when done with it.
         /// </remarks>
-        public static IntPtr Py3UnicodePy2StringtoPtr(string s)
+        public unsafe static IntPtr Py3UnicodePy2StringtoPtr(string s)
         {
-            return Runtime.IsPython3
-                ? Instance.MarshalManagedToNative(s)
-                : Marshal.StringToHGlobalAnsi(s);
+            if (Runtime.IsPython3)
+            {
+                int stringBytesCount = PyEncoding.GetByteCount(s);
+                IntPtr mem = Marshal.AllocHGlobal(stringBytesCount + 4);
+                fixed (char* str = s)
+                {
+                    try
+                    {
+                        PyEncoding.GetBytes(str, s.Length, (byte*)mem, stringBytesCount);
+                    }
+                    catch
+                    {
+                        // Do nothing with this. Very strange problem.
+                    }
+
+                    *(int*)(mem + stringBytesCount) = 0;
+                }
+                return mem;
+            }
+
+            return Marshal.StringToHGlobalAnsi(s);
         }
 
         /// <summary>
@@ -208,7 +259,12 @@ internal class Utf8Marshaler : MarshalerBase
         private static readonly MarshalerBase Instance = new Utf8Marshaler();
         private static readonly Encoding PyEncoding = Encoding.UTF8;
 
-        public override IntPtr MarshalManagedToNative(object managedObj)
+        private const int MaxStringLength = 100;
+
+        private static readonly EncodedStringsFifoDictionary EncodedStringsDictionary =
+            new EncodedStringsFifoDictionary(10000, 4 * (MaxStringLength + 1));
+
+        public override unsafe IntPtr MarshalManagedToNative(object managedObj)
         {
             var s = managedObj as string;
 
@@ -217,21 +273,49 @@ public override IntPtr MarshalManagedToNative(object managedObj)
                 return IntPtr.Zero;
             }
 
-            byte[] bStr = PyEncoding.GetBytes(s + "\0");
-            IntPtr mem = Marshal.AllocHGlobal(bStr.Length);
-            try
+            IntPtr mem;
+            int stringBytesCount;
+            if (s.Length <= MaxStringLength)
             {
-                Marshal.Copy(bStr, 0, mem, bStr.Length);
+                if (EncodedStringsDictionary.TryGetValue(s, out mem))
+                {
+                    return mem;
+                }
+
+                stringBytesCount = PyEncoding.GetByteCount(s);
+                mem = EncodedStringsDictionary.AddUnsafe(s);
             }
-            catch (Exception)
+            else
             {
-                Marshal.FreeHGlobal(mem);
-                throw;
+                stringBytesCount = PyEncoding.GetByteCount(s);
+                mem = Marshal.AllocHGlobal(stringBytesCount + 1);
+            }
+
+            fixed (char* str = s)
+            {
+                try
+                {
+                    PyEncoding.GetBytes(str, s.Length, (byte*)mem, stringBytesCount);
+                }
+                catch
+                {
+                    // Do nothing with this. Very strange problem.
+                }
+
+                ((byte*)mem)[stringBytesCount] = 0;
             }
 
             return mem;
         }
 
+        public override void CleanUpNativeData(IntPtr pNativeData)
+        {
+            if (!EncodedStringsDictionary.IsKnownPtr(pNativeData))
+            {
+                base.CleanUpNativeData(pNativeData);
+            }
+        }
+
         public static ICustomMarshaler GetInstance(string cookie)
         {
             return Instance;

diff --git a/src/runtime/Python.Runtime.csproj b/src/runtime/Python.Runtime.csproj
@@ -76,6 +76,12 @@
     <Reference Include="System" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="perf_utils\EncodedStringsFifoDictionary.cs" />
+    <Compile Include="perf_utils\EncodingGetStringPolyfill.cs" />
+    <Compile Include="perf_utils\FifoDictionary.cs" />
+    <Compile Include="perf_utils\RawImmutableMemBlock.cs" />
+    <Compile Include="perf_utils\RawMemoryFifoDictionary.cs" />
+    <Compile Include="perf_utils\RawMemUtils.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="..\SharedAssemblyInfo.cs">
       <Link>Properties\SharedAssemblyInfo.cs</Link>

diff --git a/src/runtime/assemblymanager.cs b/src/runtime/assemblymanager.cs
@@ -24,14 +24,15 @@ internal class AssemblyManager
         //    than it can end up referring to assemblies that are already unloaded (default behavior after unload appDomain - 
         //     unless LoaderOptimization.MultiDomain is used);
         //    So for multidomain support it is better to have the dict. recreated for each app-domain initialization
-        private static ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>> namespaces;
+        private static ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>> namespaces =
+            new ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>>();
 
         //private static Dictionary<string, Dictionary<string, string>> generics;
         private static AssemblyLoadEventHandler lhandler;
         private static ResolveEventHandler rhandler;
 
         // updated only under GIL?
-        private static Dictionary<string, int> probed;
+        private static Dictionary<string, int> probed = new Dictionary<string, int>(32);
 
         // modified from event handlers below, potentially triggered from different .NET threads
         private static ConcurrentQueue<Assembly> assemblies;
@@ -48,10 +49,7 @@ private AssemblyManager()
         /// </summary>
         internal static void Initialize()
         {
-            namespaces = new ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>>();
-            probed = new Dictionary<string, int>(32);
-            //generics = new Dictionary<string, Dictionary<string, string>>();
-            assemblies = new ConcurrentQueue<Assembly>();
+            assemblies = new AssemblyList(16);
             pypath = new List<string>(16);
 
             AppDomain domain = AppDomain.CurrentDomain;