[caffe2] Avoid some double (and triple) lookups in workspace (#53319)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53319

Noticed these in profiles.

Also switch to `unordered_map`.

Test Plan: Unit tests.

Reviewed By: swolchok

Differential Revision: D26504408

fbshipit-source-id: 9e14d55909a4af019058b8c27c67ee2348cd02a9

caffe2/core/workspace.cc

@@ -84,7 +84,7 @@ vector<string> Workspace::Blobs() const {
     names.push_back(entry.first);
   }
   for (const auto& forwarded : forwarded_blobs_) {
-    const auto parent_ws = forwarded.second.first;
+    const auto* parent_ws = forwarded.second.first;
     const auto& parent_name = forwarded.second.second;
     if (parent_ws->HasBlob(parent_name)) {
       names.push_back(forwarded.first);
@@ -112,13 +112,14 @@ Blob* Workspace::CreateBlob(const string& name) {
 }
 
 Blob* Workspace::CreateLocalBlob(const string& name) {
-  if (blob_map_.count(name)) {
+  auto p = blob_map_.emplace(name, nullptr);
+  if (!p.second) {
     VLOG(1) << "Blob " << name << " already exists. Skipping.";
   } else {
     VLOG(1) << "Creating blob " << name;
-    blob_map_[name] = unique_ptr<Blob>(new Blob());
+    p.first->second = std::make_unique<Blob>();
   }
-  return GetBlob(name);
+  return p.first->second.get();
 }
 
 Blob* Workspace::RenameBlob(const string& old_name, const string& new_name) {
@@ -158,15 +159,28 @@ bool Workspace::RemoveBlob(const string& name) {
 }
 
 const Blob* Workspace::GetBlob(const string& name) const {
-  if (blob_map_.count(name)) {
-    return blob_map_.at(name).get();
-  } else if (forwarded_blobs_.count(name)) {
-    const auto parent_ws = forwarded_blobs_.at(name).first;
-    const auto& parent_name = forwarded_blobs_.at(name).second;
-    return parent_ws->GetBlob(parent_name);
-  } else if (shared_ && shared_->HasBlob(name)) {
-    return shared_->GetBlob(name);
+  {
+    auto it = blob_map_.find(name);
+    if (it != blob_map_.end()) {
+      return it->second.get();
+    }
   }
+
+  {
+    auto it = forwarded_blobs_.find(name);
+    if (it != forwarded_blobs_.end()) {
+      const auto* parent_ws = it->second.first;
+      const auto& parent_name = it->second.second;
+      return parent_ws->GetBlob(parent_name);
+    }
+  }
+
+  if (shared_) {
+    if (auto blob = shared_->GetBlob(name)) {
+      return blob;
+    }
+  }
+
   LOG(WARNING) << "Blob " << name << " not in the workspace.";
   // TODO(Yangqing): do we want to always print out the list of blobs here?
   // LOG(WARNING) << "Current blobs:";
@@ -249,25 +263,25 @@ NetBase* Workspace::CreateNet(
 }
 
 NetBase* Workspace::GetNet(const string& name) {
-  if (!net_map_.count(name)) {
-    return nullptr;
-  } else {
-    return net_map_[name].get();
+  auto it = net_map_.find(name);
+  if (it != net_map_.end()) {
+    return it->second.get();
   }
+
+  return nullptr;
 }
 
 void Workspace::DeleteNet(const string& name) {
-  if (net_map_.count(name)) {
-    net_map_.erase(name);
-  }
+  net_map_.erase(name);
 }
 
 bool Workspace::RunNet(const string& name) {
-  if (!net_map_.count(name)) {
+  auto it = net_map_.find(name);
+  if (it == net_map_.end()) {
     LOG(ERROR) << "Network " << name << " does not exist yet.";
     return false;
   }
-  return net_map_[name]->Run();
+  return it->second->Run();
 }
 
 bool Workspace::RunOperatorOnce(const OperatorDef& op_def) {

caffe2/core/workspace.h

@@ -8,6 +8,7 @@
 #include <cstddef>
 #include <mutex>
 #include <typeinfo>
+#include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
@@ -47,8 +48,6 @@ struct TORCH_API StopOnSignal {
 class TORCH_API Workspace {
  public:
   typedef std::function<bool(int)> ShouldContinue;
-  typedef CaffeMap<string, unique_ptr<Blob> > BlobMap;
-  typedef CaffeMap<string, unique_ptr<NetBase> > NetMap;
   /**
    * Initializes an empty workspace.
    */
@@ -136,10 +135,11 @@ class TORCH_API Workspace {
   template <class Context>
   void CopyForwardedTensors(const std::unordered_set<std::string>& blobs) {
     for (const auto& blob : blobs) {
-      if (!forwarded_blobs_.count(blob)) {
+      auto it = forwarded_blobs_.find(blob);
+      if (it == forwarded_blobs_.end()) {
         continue;
       }
-      const auto& ws_blob = forwarded_blobs_[blob];
+      const auto& ws_blob = it->second;
       const auto* parent_ws = ws_blob.first;
       auto* from_blob = parent_ws->GetBlob(ws_blob.second);
       CAFFE_ENFORCE(from_blob);
@@ -181,13 +181,19 @@ class TORCH_API Workspace {
     // Then, check the forwarding map, then the parent workspace
     if (blob_map_.count(name)) {
       return true;
-    } else if (forwarded_blobs_.count(name)) {
-      const auto parent_ws = forwarded_blobs_.at(name).first;
-      const auto& parent_name = forwarded_blobs_.at(name).second;
+    }
+
+    auto it = forwarded_blobs_.find(name);
+    if (it != forwarded_blobs_.end()) {
+      const auto parent_ws = it->second.first;
+      const auto& parent_name = it->second.second;
       return parent_ws->HasBlob(parent_name);
-    } else if (shared_) {
+    }
+
+    if (shared_) {
       return shared_->HasBlob(name);
     }
+
     return false;
   }
 
@@ -318,7 +324,7 @@ class TORCH_API Workspace {
 
   static std::shared_ptr<Bookkeeper> bookkeeper();
 
-  BlobMap blob_map_;
+  std::unordered_map<string, unique_ptr<Blob>> blob_map_;
   const string root_folder_;
   const Workspace* shared_;
   std::unordered_map<string, std::pair<const Workspace*, string>>
@@ -326,7 +332,7 @@ class TORCH_API Workspace {
   std::unique_ptr<ThreadPool> thread_pool_;
   std::mutex thread_pool_creation_mutex_;
   std::shared_ptr<Bookkeeper> bookkeeper_;
-  NetMap net_map_;
+  std::unordered_map<string, unique_ptr<NetBase>> net_map_;
 
   C10_DISABLE_COPY_AND_ASSIGN(Workspace);
 };