diff --git a/change_log.txt b/change_log.txt
index f8460831..87406797 100644
--- a/change_log.txt
+++ b/change_log.txt
@@ -1,4 +1,7 @@
  ===== 3.1.28-dev===== (xx.xx.2015)
+ 18.10.2015
+  - optimize filepath normalization
+  
  18.09.2015
   - bugfix {if $foo instanceof $bar} failed to compile if 2nd value is a variable https://github.com/smarty-php/smarty/issues/92
   
diff --git a/libs/Smarty.class.php b/libs/Smarty.class.php
index 3574dcf0..037cbabf 100644
--- a/libs/Smarty.class.php
+++ b/libs/Smarty.class.php
@@ -1146,17 +1146,22 @@ class Smarty extends Smarty_Internal_TemplateBase
     public function _realpath($path, $realpath = null)
     {
         static $pattern = null;
-        static $pattern2 = null;
+        static $nds = null;
         if ($pattern == null) {
-            $pattern = '#[' . (DS == '/' ? '\\\\' : '/') . ']|([\\\/]([\\\/]|([.]+[\\\/])))#';
-            $pattern2 = '#([\\\/]+[^\\\/]+[\\\/]+[.]([\\\/]+[.])*[.][\\\/]+([.][\\\/]+)*)|([\\\/]+([.][\\\/]+)+)|[\\\/]{2,}|[' .
-                (DS == '/' ? '\\\\' : '/') . ']+#';
+            $nds = DS == '/' ? '\\' : '/';
+            $ds = '\\' . DS;
+            $pattern = "#([{$ds}]+[^{$ds}]+[{$ds}]+[.]([{$ds}]+[.])*[.][{$ds}]+([.][{$ds}]+)*)|([{$ds}]+([.][{$ds}]+)+)|[{$ds}]{2,}#";
         }
+        // normalize DS
+        if (strpos($path, $nds) !== false) {
+            $path = str_replace($nds, DS, $path);
+        }
+
         if ($realpath === true && $path[0] !== '/' && $path[1] !== ':') {
             $path = getcwd() . DS . $path;
         }
-        while (preg_match($pattern, $path)) {
-            $path = preg_replace($pattern2, DS, $path);
+        while ((strpos($path, '.' . DS) !== false) || (strpos($path, DS . DS) !== false)) {
+            $path = preg_replace($pattern, DS, $path);
         }
         if ($realpath === false && ($path[0] == '/' || $path[1] == ':')) {
             $path = str_ireplace(getcwd(), '.', $path);
diff --git a/libs/sysplugins/smarty_internal_resource_file.php b/libs/sysplugins/smarty_internal_resource_file.php
index d41b0fc8..0b7055a7 100644
--- a/libs/sysplugins/smarty_internal_resource_file.php
+++ b/libs/sysplugins/smarty_internal_resource_file.php
@@ -49,6 +49,10 @@ class Smarty_Internal_Resource_File extends Smarty_Resource
             // files relative to a template only get one shot
             return is_file($path) ? $path : false;
         }
+        // normalize DS
+        if (strpos($file, DS == '/' ? '\\' : '/') !== false) {
+            $file = str_replace(DS == '/' ? '\\' : '/', DS, $file);
+        }
 
         $_directories = $source->smarty->getTemplateDir(null, $source->isConfig);
         // template_dir index?
@@ -87,7 +91,7 @@ class Smarty_Internal_Resource_File extends Smarty_Resource
         foreach ($_directories as $_directory) {
             $path = $_directory . $file;
             if (is_file($path)) {
-                return $source->smarty->_realpath($path);
+                return (strpos($path, '.' . DS) !== false) ? $source->smarty->_realpath($path) : $path;
             }
         }
         if (!isset($_index_dirs)) {