Make a function to be const member function in partitioner if possibl…

…e. (#3150)

Summary:
This PR is created from the following discussion.
#3142 (comment)

Basically,  in Partitioner, some functions were not const member function (although it won't modify any value in this class), and they can't be used in const class objects.  This PR marks those functions as const.

Documentation:

[Optional Fixes #issue]
Pull Request resolved: #3150

Test Plan: Please see a detailed explanation of how to fill out the fields in the relevant sections in PULL_REQUEST.md.

Differential Revision: D15926744

Pulled By: beicy

fbshipit-source-id: 1cf5e9a69719efa586f86b68c185d2375c3893b7

include/glow/Partitioner/Partitioner.h

@@ -86,7 +86,7 @@ class NodeToFunctionMap {
     functionToBackendName_[F] = backendName;
   }
 
-  std::string getPartitionBackendName(Function *F) {
+  std::string getPartitionBackendName(Function *F) const {
     DCHECK(functionToBackendName_.find(F) != functionToBackendName_.end())
         << "Unknown partition in Function: " << F->getName().str();
     return functionToBackendName_.find(F)->second;
@@ -99,8 +99,11 @@ class NodeToFunctionMap {
   const FunctionList &getPartitions() const { return functions_; }
 
   /// Get the list of logical device ID related to this function \p F.
-  std::vector<DeviceIDTy> getLogicalDeviceIDList(Function *F) {
-    return logicalDeviceIDMap_[F];
+  const std::vector<DeviceIDTy> getLogicalDeviceIDList(Function *F) const {
+    if (logicalDeviceIDMap_.find(F) == logicalDeviceIDMap_.end()) {
+      return {};
+    }
+    return logicalDeviceIDMap_.at(F);
   }
 
   void appendLogicalDeviceID(Function *F, DeviceIDTy id) {
@@ -144,7 +147,12 @@ class NodeToFunctionMap {
   }
 
   /// Get the memory consumption for a partition \p func.
-  GraphMemInfo getGraphMemInfo(Function *func) { return partitionCost_[func]; }
+  GraphMemInfo getGraphMemInfo(Function *func) const {
+    if (partitionCost_.find(func) == partitionCost_.end()) {
+      return GraphMemInfo{};
+    }
+    return partitionCost_.find(func)->second;
+  }
 };
 
 /// Given a module, partitions each of the its functions into multiple ones
@@ -231,11 +239,12 @@ class Partitioner {
   /// Check if \p partitions satisfies number of physical devices restriction.
   /// I.e. check if the number of logical devices is less than the given
   /// physical devices.
-  llvm::Error logicalDevicesValidation(NodeToFunctionMap &partitions);
+  llvm::Error
+  logicalDevicesValidation(const NodeToFunctionMap &partitions) const;
 
   /// Check if the memory usage of each partition meets the physical device
   /// memory restriction.
-  llvm::Error memoryUsageValidation(NodeToFunctionMap &partitions);
+  llvm::Error memoryUsageValidation(const NodeToFunctionMap &partitions) const;
 
   /// Duplicates all networks in the module order to saturate the Host.
   void saturateHost(unsigned logicalDeviceCount);

lib/Partitioner/Partitioner.cpp

@@ -105,8 +105,8 @@ void Partitioner::dumpDAG(llvm::StringRef dotFilename) const {
   return;
 }
 
-llvm::Error
-Partitioner::logicalDevicesValidation(NodeToFunctionMap &partitions) {
+llvm::Error Partitioner::logicalDevicesValidation(
+    const NodeToFunctionMap &partitions) const {
   std::map<std::string, std::set<DeviceIDTy>> partitionsNum;
   for (auto &func : partitions.getPartitions()) {
     auto backendName = partitions.getPartitionBackendName(func);
@@ -117,27 +117,30 @@ Partitioner::logicalDevicesValidation(NodeToFunctionMap &partitions) {
     for (size_t i = 0, e = logicalIDList.size(); i < e; i++) {
       partitionsNum[backendName].insert(logicalIDList[i]);
     }
+    auto backendNum = backendMap_.at(backendName).num;
     RETURN_ERR_IF_NOT(
-        partitionsNum[backendName].size() <= backendMap_[backendName].num,
+        partitionsNum[backendName].size() <= backendNum,
         llvm::formatv("Partition failed: the number of given({0}) devices({1}) "
                       "is fewer than the required minimal partitions({2}).",
-                      backendName, backendMap_[backendName].num,
+                      backendName, backendNum,
                       partitionsNum[backendName].size())
             .str());
   }
   return llvm::Error::success();
 }
 
-llvm::Error Partitioner::memoryUsageValidation(NodeToFunctionMap &partitions) {
+llvm::Error
+Partitioner::memoryUsageValidation(const NodeToFunctionMap &partitions) const {
   for (auto &func : partitions.getPartitions()) {
     auto backendName = partitions.getPartitionBackendName(func);
     auto usedMemSize = partitions.getGraphMemInfo(func).getTotalMemSize();
+    auto availableMemSize = backendMap_.at(backendName).memSize;
     RETURN_ERR_IF_NOT(
-        usedMemSize <= backendMap_[backendName].memSize,
+        usedMemSize <= availableMemSize,
         llvm::formatv(
             "Partition failed: the memory usage({0}) of one partition exceeds "
             "the available memory({1}) of given devices({2}).",
-            usedMemSize, backendMap_[backendName].memSize, backendName)
+            usedMemSize, availableMemSize, backendName)
             .str());
   }
   return llvm::Error::success();