Caches iterators instead of invoking function calls on every iteration.

This caches iterators, i.e. especially the end iterator when possible.

The problem:

    for (auto it = begin(seq); it != end(seq); ++it)

this has to call `end(seq)` on every iteration, since the compiler is
not able to reason about the call's site effects (to bad, huh).

Instead do it like this:

    for (auto it = begin(seq), end = end(seq); it != end; ++it)

caching the end iterator.

Of course, still better would be:

    for (auto&& each : seq)

if all you want is value semantics.

Why `auto&&` you may ask? Because it binds to everything and never copies!

Skim the referenced proposal (that was rejected, but nevertheless) for a
detailed explanation on range-based for loops and why `auto&&` is great.

Reference:

- http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3853.htm

contractor/contractor.hpp

@@ -312,7 +312,7 @@ class Contractor
         tbb::parallel_for(tbb::blocked_range<int>(0, number_of_nodes, InitGrainSize),
                           [&remaining_nodes](const tbb::blocked_range<int> &range)
                           {
-                              for (int x = range.begin(); x != range.end(); ++x)
+                              for (int x = range.begin(), end = range.end(); x != end; ++x)
                               {
                                   remaining_nodes[x].id = x;
                               }
@@ -324,7 +324,7 @@ class Contractor
                               const tbb::blocked_range<int> &range)
                           {
                               ContractorThreadData *data = thread_data_list.getThreadData();
-                              for (int x = range.begin(); x != range.end(); ++x)
+                              for (int x = range.begin(), end = range.end(); x != end; ++x)
                               {
                                   node_priorities[x] =
                                       this->EvaluateNodePriority(data, &node_data[x], x);
@@ -430,7 +430,7 @@ class Contractor
                               {
                                   ContractorThreadData *data = thread_data_list.getThreadData();
                                   // determine independent node set
-                                  for (int i = range.begin(); i != range.end(); ++i)
+                                  for (int i = range.begin(), end = range.end(); i != end; ++i)
                                   {
                                       const NodeID node = remaining_nodes[i].id;
                                       remaining_nodes[i].is_independent =
@@ -451,7 +451,7 @@ class Contractor
                 [this, &remaining_nodes, &thread_data_list](const tbb::blocked_range<int> &range)
                 {
                     ContractorThreadData *data = thread_data_list.getThreadData();
-                    for (int position = range.begin(); position != range.end(); ++position)
+                    for (int position = range.begin(), end = range.end(); position != end; ++position)
                     {
                         const NodeID x = remaining_nodes[position].id;
                         this->ContractNode<false>(data, x);
@@ -470,7 +470,7 @@ class Contractor
                 [this, &remaining_nodes, &thread_data_list](const tbb::blocked_range<int> &range)
                 {
                     ContractorThreadData *data = thread_data_list.getThreadData();
-                    for (int position = range.begin(); position != range.end(); ++position)
+                    for (int position = range.begin(), end = range.end(); position != end; ++position)
                     {
                         const NodeID x = remaining_nodes[position].id;
                         this->DeleteIncomingEdges(data, x);
@@ -508,7 +508,7 @@ class Contractor
                     const tbb::blocked_range<int> &range)
                 {
                     ContractorThreadData *data = thread_data_list.getThreadData();
-                    for (int position = range.begin(); position != range.end(); ++position)
+                    for (int position = range.begin(), end = range.end(); position != end; ++position)
                     {
                         NodeID x = remaining_nodes[position].id;
                         this->UpdateNodeNeighbours(node_priorities, node_data, data, x);

data_structures/static_rtree.hpp

@@ -365,8 +365,8 @@ class StaticRTree
             [&input_data_vector, &input_wrapper_vector, &get_hilbert_number, &coordinate_list](
                 const tbb::blocked_range<uint64_t> &range)
             {
-                for (uint64_t element_counter = range.begin(); element_counter != range.end();
-                     ++element_counter)
+                for (uint64_t element_counter = range.begin(), end = range.end();
+                     element_counter != end; ++element_counter)
                 {
                     WrappedInputElement &current_wrapper = input_wrapper_vector[element_counter];
                     current_wrapper.m_array_index = element_counter;
@@ -476,7 +476,7 @@ class StaticRTree
         tbb::parallel_for(tbb::blocked_range<uint32_t>(0, search_tree_size),
                           [this, &search_tree_size](const tbb::blocked_range<uint32_t> &range)
                           {
-                              for (uint32_t i = range.begin(); i != range.end(); ++i)
+                              for (uint32_t i = range.begin(), end = range.end(); i != end; ++i)
                               {
                                   TreeNode &current_tree_node = this->m_search_tree[i];
                                   for (uint32_t j = 0; j < current_tree_node.child_count; ++j)
@@ -664,7 +664,8 @@ class StaticRTree
         while (!traversal_queue.empty())
         {
             const IncrementalQueryCandidate current_query_node = traversal_queue.top();
-            if (current_query_node.min_dist > max_distance && inspected_elements > max_checked_elements)
+            if (current_query_node.min_dist > max_distance &&
+                inspected_elements > max_checked_elements)
             {
                 break;
             }
@@ -760,7 +761,7 @@ class StaticRTree
 
             // stop the search by flushing the queue
             if (result_phantom_node_vector.size() >= max_number_of_phantom_nodes &&
-                 number_of_elements_from_big_cc > 0)
+                number_of_elements_from_big_cc > 0)
             {
                 traversal_queue = std::priority_queue<IncrementalQueryCandidate>{};
             }
@@ -804,7 +805,8 @@ class StaticRTree
             const IncrementalQueryCandidate current_query_node = traversal_queue.top();
             traversal_queue.pop();
 
-            if (current_query_node.min_dist > max_distance || inspected_elements >= max_checked_elements)
+            if (current_query_node.min_dist > max_distance ||
+                inspected_elements >= max_checked_elements)
             {
                 break;
             }

extractor/extraction_containers.cpp

@@ -169,9 +169,12 @@ void ExtractionContainers::PrepareNodes()
     external_to_internal_node_id_map.reserve(used_node_id_list.size());
     auto node_iter = all_nodes_list.begin();
     auto ref_iter = used_node_id_list.begin();
+    const auto all_nodes_list_end = all_nodes_list.end();
+    const auto used_node_id_list_end = used_node_id_list.end();
     auto internal_id = 0u;
+
     // compute the intersection of nodes that were referenced and nodes we actually have
-    while (node_iter != all_nodes_list.end() && ref_iter != used_node_id_list.end())
+    while (node_iter != all_nodes_list_end && ref_iter != used_node_id_list_end)
     {
         if (node_iter->node_id < *ref_iter)
         {
@@ -208,7 +211,11 @@ void ExtractionContainers::PrepareEdges(lua_State *segment_state)
     // Traverse list of edges and nodes in parallel and set start coord
     auto node_iterator = all_nodes_list.begin();
     auto edge_iterator = all_edges_list.begin();
-    while (edge_iterator != all_edges_list.end() && node_iterator != all_nodes_list.end())
+
+    const auto all_edges_list_end = all_edges_list.end();
+    const auto all_nodes_list_end = all_nodes_list.end();
+
+    while (edge_iterator != all_edges_list_end && node_iterator != all_nodes_list_end)
     {
         if (edge_iterator->result.source < node_iterator->node_id)
         {
@@ -259,7 +266,10 @@ void ExtractionContainers::PrepareEdges(lua_State *segment_state)
     TIMER_START(compute_weights);
     node_iterator = all_nodes_list.begin();
     edge_iterator = all_edges_list.begin();
-    while (edge_iterator != all_edges_list.end() && node_iterator != all_nodes_list.end())
+    const auto all_edges_list_end_ = all_edges_list.end();
+    const auto all_nodes_list_end_ = all_nodes_list.end();
+
+    while (edge_iterator != all_edges_list_end_ && node_iterator != all_nodes_list_end_)
     {
         // skip all invalid edges
         if (edge_iterator->result.source == SPECIAL_NODEID)
@@ -475,7 +485,10 @@ void ExtractionContainers::WriteNodes(std::ofstream& file_out_stream) const
     // identify all used nodes by a merging step of two sorted lists
     auto node_iterator = all_nodes_list.begin();
     auto node_id_iterator = used_node_id_list.begin();
-    while (node_id_iterator != used_node_id_list.end() && node_iterator != all_nodes_list.end())
+    const auto used_node_id_list_end = used_node_id_list.end();
+    const auto all_nodes_list_end = all_nodes_list.end();
+
+    while (node_id_iterator != used_node_id_list_end && node_iterator != all_nodes_list_end)
     {
         if (*node_id_iterator < node_iterator->node_id)
         {
@@ -550,9 +563,11 @@ void ExtractionContainers::PrepareRestrictions()
     TIMER_START(fix_restriction_starts);
     auto restrictions_iterator = restrictions_list.begin();
     auto way_start_and_end_iterator = way_start_end_id_list.cbegin();
+    const auto restrictions_list_end = restrictions_list.end();
+    const auto way_start_end_id_list_end = way_start_end_id_list.cend();
 
-    while (way_start_and_end_iterator != way_start_end_id_list.cend() &&
-           restrictions_iterator != restrictions_list.end())
+    while (way_start_and_end_iterator != way_start_end_id_list_end &&
+           restrictions_iterator != restrictions_list_end)
     {
         if (way_start_and_end_iterator->way_id < restrictions_iterator->restriction.from.way)
         {
@@ -616,8 +631,11 @@ void ExtractionContainers::PrepareRestrictions()
     TIMER_START(fix_restriction_ends);
     restrictions_iterator = restrictions_list.begin();
     way_start_and_end_iterator = way_start_end_id_list.cbegin();
-    while (way_start_and_end_iterator != way_start_end_id_list.cend() &&
-           restrictions_iterator != restrictions_list.end())
+    const auto way_start_end_id_list_end_ = way_start_end_id_list.cend();
+    const auto restrictions_list_end_ = restrictions_list.end();
+
+    while (way_start_and_end_iterator != way_start_end_id_list_end_ &&
+           restrictions_iterator != restrictions_list_end_)
     {
         if (way_start_and_end_iterator->way_id < restrictions_iterator->restriction.to.way)
         {

extractor/extractor.cpp

@@ -161,7 +161,7 @@ int extractor::run()
         {
             // create a vector of iterators into the buffer
             std::vector<osmium::memory::Buffer::const_iterator> osm_elements;
-            for (auto iter = std::begin(buffer); iter != std::end(buffer); ++iter)
+            for (auto iter = std::begin(buffer), end = std::end(buffer); iter != end; ++iter)
             {
                 osm_elements.push_back(iter);
             }
@@ -180,7 +180,7 @@ int extractor::run()
                     ExtractionWay result_way;
                     lua_State *local_state = scripting_environment.get_lua_state();
 
-                    for (auto x = range.begin(); x != range.end(); ++x)
+                    for (auto x = range.begin(), end = range.end(); x != end; ++x)
                     {
                         const auto entity = osm_elements[x];
 

util/json_renderer.hpp

@@ -61,12 +61,11 @@ struct Renderer : mapbox::util::static_visitor<>
     void operator()(const Object &object) const
     {
         out << "{";
-        auto iterator = object.values.begin();
-        while (iterator != object.values.end())
+        for (auto it = object.values.begin(), end = object.values.end(); it != end;)
         {
-            out << "\"" << (*iterator).first << "\":";
-            mapbox::util::apply_visitor(Renderer(out), (*iterator).second);
-            if (++iterator != object.values.end())
+            out << "\"" << it->first << "\":";
+            mapbox::util::apply_visitor(Renderer(out), it->second);
+            if (++it != end)
             {
                 out << ",";
             }
@@ -77,12 +76,10 @@ struct Renderer : mapbox::util::static_visitor<>
     void operator()(const Array &array) const
     {
         out << "[";
-        std::vector<Value>::const_iterator iterator;
-        iterator = array.values.begin();
-        while (iterator != array.values.end())
+        for (auto it = array.values.cend(), end = array.values.cend(); it != end;)
         {
-            mapbox::util::apply_visitor(Renderer(out), *iterator);
-            if (++iterator != array.values.end())
+            mapbox::util::apply_visitor(Renderer(out), *it);
+            if (++it != end)
             {
                 out << ",";
             }
@@ -121,16 +118,15 @@ struct ArrayRenderer : mapbox::util::static_visitor<>
     void operator()(const Object &object) const
     {
         out.push_back('{');
-        auto iterator = object.values.begin();
-        while (iterator != object.values.end())
+        for (auto it = object.values.begin(), end = object.values.end(); it != end;)
         {
             out.push_back('\"');
-            out.insert(out.end(), (*iterator).first.begin(), (*iterator).first.end());
+            out.insert(out.end(), it->first.begin(), it->first.end());
             out.push_back('\"');
             out.push_back(':');
 
-            mapbox::util::apply_visitor(ArrayRenderer(out), (*iterator).second);
-            if (++iterator != object.values.end())
+            mapbox::util::apply_visitor(ArrayRenderer(out), it->second);
+            if (++it != end)
             {
                 out.push_back(',');
             }
@@ -141,12 +137,10 @@ struct ArrayRenderer : mapbox::util::static_visitor<>
     void operator()(const Array &array) const
     {
         out.push_back('[');
-        std::vector<Value>::const_iterator iterator;
-        iterator = array.values.begin();
-        while (iterator != array.values.end())
+        for (auto it = array.values.cbegin(), end = array.values.cend(); it != end;)
         {
-            mapbox::util::apply_visitor(ArrayRenderer(out), *iterator);
-            if (++iterator != array.values.end())
+            mapbox::util::apply_visitor(ArrayRenderer(out), *it);
+            if (++it != end)
             {
                 out.push_back(',');
             }

util/string_util.hpp

@@ -132,9 +132,10 @@ inline std::string escape_JSON(const std::string &input)
 inline std::size_t URIDecode(const std::string &input, std::string &output)
 {
     auto src_iter = std::begin(input);
+    const auto src_end = std::end(input);
     output.resize(input.size() + 1);
     std::size_t decoded_length = 0;
-    for (decoded_length = 0; src_iter != std::end(input); ++decoded_length)
+    for (decoded_length = 0; src_iter != src_end; ++decoded_length)
     {
         if (src_iter[0] == '%' && src_iter[1] && src_iter[2] && isxdigit(src_iter[1]) &&
             isxdigit(src_iter[2]))

util/xml_renderer.hpp

@@ -56,38 +56,33 @@ struct XMLToArrayRenderer : mapbox::util::static_visitor<>
 
     void operator()(const Object &object) const
     {
-        auto iterator = object.values.begin();
-        while (iterator != object.values.end())
+        for (auto &&each : object.values)
         {
-            if (iterator->first.at(0) != '_')
+            if (each.first.at(0) != '_')
             {
                 out.push_back('<');
-                out.insert(out.end(), (*iterator).first.begin(), (*iterator).first.end());
+                out.insert(out.end(), each.first.begin(), each.first.end());
             }
             else
             {
                 out.push_back(' ');
-                out.insert(out.end(), ++(*iterator).first.begin(), (*iterator).first.end());
+                out.insert(out.end(), ++(each).first.begin(), each.first.end());
                 out.push_back('=');
             }
-            mapbox::util::apply_visitor(XMLToArrayRenderer(out), (*iterator).second);
-            if (iterator->first.at(0) != '_')
+            mapbox::util::apply_visitor(XMLToArrayRenderer(out), each.second);
+            if (each.first.at(0) != '_')
             {
                 out.push_back('/');
                 out.push_back('>');
             }
-            ++iterator;
         }
     }
 
     void operator()(const Array &array) const
     {
-        std::vector<Value>::const_iterator iterator;
-        iterator = array.values.begin();
-        while (iterator != array.values.end())
+        for (auto &&each : array.values)
         {
-            mapbox::util::apply_visitor(XMLToArrayRenderer(out), *iterator);
-            ++iterator;
+            mapbox::util::apply_visitor(XMLToArrayRenderer(out), each);
         }
     }