From a5bf6744190cdb38621699e5e34c7e615dfd1e2d Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Wed, 9 Jan 2019 00:23:23 -0500
Subject: [PATCH] [Input] Cache parsed YAML files to speed up repeated reads

---
 include/cantera/base/AnyMap.h |  6 ++++++
 src/base/AnyMap.cpp           | 32 ++++++++++++++++++++++++++++----
 src/base/application.cpp      |  2 +-
 src/base/application.h        |  2 ++
 4 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/include/cantera/base/AnyMap.h b/include/cantera/base/AnyMap.h
index 594caf8bc..0aa0b44e8 100644
--- a/include/cantera/base/AnyMap.h
+++ b/include/cantera/base/AnyMap.h
@@ -340,6 +340,12 @@ private:
 
     std::unordered_map<std::string, AnyValue> m_data;
     UnitSystem m_units;
+
+    //! Cache for previously-parsed input (YAML) files. The key is the full path
+    //! to the file, and the second element of the value is the last-modified
+    //! time for the file, which is used to enable change detection.
+    static std::unordered_map<std::string, std::pair<AnyMap, int>> s_cache;
+
     friend class AnyValue;
 };
 
diff --git a/src/base/AnyMap.cpp b/src/base/AnyMap.cpp
index 4871053cf..ee4052790 100644
--- a/src/base/AnyMap.cpp
+++ b/src/base/AnyMap.cpp
@@ -4,6 +4,7 @@
 // at http://www.cantera.org/license.txt for license and copyright information.
 
 #include "cantera/base/AnyMap.h"
+#include "application.h"
 #include "cantera/base/yaml.h"
 #include "cantera/base/stringUtils.h"
 #ifdef CT_USE_DEMANGLE
@@ -12,11 +13,14 @@
 
 #include <boost/algorithm/string.hpp>
 #include <fstream>
+#include <mutex>
 
 namespace ba = boost::algorithm;
 
 namespace { // helper functions
 
+std::mutex yaml_cache_mutex;
+
 bool isFloat(const std::string& val)
 {
     // This function duplicates the logic of fpValueCheck, but doesn't throw
@@ -238,6 +242,8 @@ std::map<std::string, std::string> AnyValue::s_typenames = {
     {typeid(AnyMap).name(), "AnyMap"},
 };
 
+std::unordered_map<std::string, std::pair<AnyMap, int>> AnyMap::s_cache;
+
 // Methods of class AnyValue
 
 AnyValue::AnyValue()
@@ -745,17 +751,35 @@ AnyMap AnyMap::fromYamlString(const std::string& yaml) {
 
 AnyMap AnyMap::fromYamlFile(const std::string& name) {
     std::string fullName = findInputFile(name);
-    AnyMap amap;
+    int mtime = get_modified_time(fullName);
+
+    // Check for an already-parsed YAML file with the same last-modified time,
+    // and return that if possible
+    std::unique_lock<std::mutex> lock(yaml_cache_mutex);
+    auto iter = s_cache.find(fullName);
+    if (iter != s_cache.end() && iter->second.second == mtime) {
+        return iter->second.first;
+    }
+
+    // Generate an AnyMap from the YAML file and store it in the cache
+    auto& cache_item = s_cache[fullName];
+    cache_item.second = mtime;
     try {
         YAML::Node node = YAML::LoadFile(fullName);
-        amap = node.as<AnyMap>();
+        cache_item.first = node.as<AnyMap>();
+        cache_item.first.applyUnits(UnitSystem());
     } catch (YAML::Exception& err) {
         std::ifstream infile(fullName);
+        s_cache.erase(fullName);
         throw CanteraError("AnyMap::fromYamlFile",
             formatYamlError(err, infile, name));
+    } catch (CanteraError& err) {
+        s_cache.erase(fullName);
+        throw;
     }
-    amap.applyUnits(UnitSystem());
-    return amap;
+
+    // Return a copy of the AnyMap
+    return cache_item.first;
 }
 
 AnyMap::const_iterator begin(const AnyValue& v) {
diff --git a/src/base/application.cpp b/src/base/application.cpp
index 146efaa56..a6daf1f78 100644
--- a/src/base/application.cpp
+++ b/src/base/application.cpp
@@ -38,7 +38,7 @@ static std::mutex app_mutex;
 //! Mutex for controlling access to XML file storage
 static std::mutex xml_mutex;
 
-static int get_modified_time(const std::string& path) {
+int get_modified_time(const std::string& path) {
 #ifdef _WIN32
     HANDLE hFile = CreateFile(path.c_str(), NULL, NULL,
                               NULL, OPEN_EXISTING, 0, NULL);
diff --git a/src/base/application.h b/src/base/application.h
index 9c5df3014..e268da1e2 100644
--- a/src/base/application.h
+++ b/src/base/application.h
@@ -19,6 +19,8 @@ namespace Cantera
 
 class XML_Node;
 
+int get_modified_time(const std::string& path);
+
 /*!
  * @defgroup globalData Global Data
  *