add get_noc_links(...) method

Author: soheilshahrouz

vpr/src/noc/noc_storage.cpp

@@ -64,11 +64,11 @@ NocRouter& NocStorage::get_single_mutable_noc_router(NocRouterId id) {
 }
 
 // get link properties
-const NocLink& NocStorage::get_single_noc_link(NocLinkId id) const {
+    const NocLink& NocStorage::get_single_noc_link(NocLinkId id) const {
     return link_storage[id];
 }
 
-NocLinkId  NocStorage::get_single_noc_link_id(NocRouterId src_router, NocRouterId dst_router) const {
+NocLinkId NocStorage::get_single_noc_link_id(NocRouterId src_router, NocRouterId dst_router) const {
     NocLinkId link_id = NocLinkId::INVALID();
 
     for (const auto& link : link_storage) {
@@ -209,6 +209,8 @@ void NocStorage::finished_building_noc() {
     VTR_ASSERT_MSG(!built_noc, "NoC already built, cannot modify further.");
     built_noc = true;
 
+    returnable_noc_link_const_refs_.reserve(link_storage.size());
+
     /* We go through all NoC routers in the router_storage and check if there are any
      * two consecutive NoC routers whose latency is different. If such two routers are
      * found, we set detailed_router_latency_ to True.

vpr/src/noc/noc_storage.h

@@ -133,10 +133,35 @@ class NocStorage {
      */
     double noc_router_latency;
 
+    /**
+     * @brief When set true, specifies that some NoC routers have different
+     * latencies than others. When set false, all the NoC routers have the same
+     * latency.
+     */
     bool detailed_router_latency_;
+
+    /**
+     * @brief When set true, specifies that some NoC links have different
+     * latencies than others. When set false, all the NoC link have the same
+     * latency.
+     */
     bool detailed_link_latency_;
+
+    /**
+     * @brief When set true, specifies that some NoC links have different
+     * bandwidth than others. When set false, all the NoC link have the same
+     * bandwidth.
+     */
     bool detailed_link_bandwidth_;
 
+    /**
+     * @brief A constant reference to this vector is returned by get_noc_links(...).
+     * This is used to avoid memory allocation whenever get_noc_links(...) is called.
+     * The vector is mutable so that get_noc_links(...), which is a const method, can
+     * modify it.
+     */
+    mutable std::vector<std::reference_wrapper<const NocLink>> returnable_noc_link_const_refs_;
+
     /**
      * @brief Internal reference to the device grid width. This is necessary
      * to compute a unique key for a given grid location which we can then use
@@ -204,45 +229,54 @@ class NocStorage {
      *
      * @return A vector of links.
      */
-    vtr::vector<NocLinkId, NocLink>& get_mutable_noc_links(void);
+    vtr::vector<NocLinkId, NocLink>& get_mutable_noc_links();
 
     /**
      * @return An integer representing the total number of links within the
      * NoC.
      */
-    int get_number_of_noc_links(void) const;
+    int get_number_of_noc_links() const;
 
     /**
      * @brief Get the maximum allowable bandwidth for a link
      * within the NoC.
      * 
      * @return a numeric value that represents the link bandwidth in bps
      */
-
-    double get_noc_link_bandwidth(void) const;
+    double get_noc_link_bandwidth() const;
 
     /**
      * @brief Get the latency of traversing through a link in
      * the NoC.
      * 
      * @return a numeric value that represents the link latency in seconds
      */
-
-    double get_noc_link_latency(void) const;
+    double get_noc_link_latency() const;
 
     /**
      * @brief Get the latency of traversing through a router in
      * the NoC.
      * 
      * @return a numeric value that represents the router latency in seconds
      */
+    double get_noc_router_latency() const;
 
-    double get_noc_router_latency(void) const;
-
+    /**
+     * @return True if some NoC routers have different latencies than others.
+     * False if all NoC routers have the same latency.
+     */
     bool get_detailed_router_latency() const;
 
+    /**
+     * @return True if some NoC links have different latencies than others.
+     * False if all NoC links have the same latency.
+     */
     bool get_detailed_link_latency() const;
 
+    /**
+     * @return True if some NoC links have different bandwidths than others.
+     * False if all NoC links have the same bandwidth.
+     */
     bool get_detailed_link_bandwidth() const;
 
     // getters for  routers
@@ -279,6 +313,18 @@ class NocStorage {
      */
     const NocLink& get_single_noc_link(NocLinkId id) const;
 
+    /**
+     *
+     * @tparam Container The type of standard library container used to carry
+     * NoCLinkIds. This container type must be iterable in a range-based loop.
+     * @param noc_link_ids A standard container that contains NoCLinkIds of the
+     * requested NoC links
+     * @return A const
+     */
+    template <template<typename> class Container>
+    const std::vector<std::reference_wrapper<const NocLink>>& get_noc_links(const Container<NocLinkId>& noc_link_ids) const;
+
+
     /**
      * @brief Given source and sink router identifiers, this function
      * finds a link connecting these routers and returns its identifier.
@@ -292,7 +338,7 @@ class NocStorage {
      * to the destination router. NocLinkId::INVALID() is such a link is not
      * found.
      */
-    NocLinkId  get_single_noc_link_id(NocRouterId src_router, NocRouterId dst_router) const;
+    NocLinkId get_single_noc_link_id(NocRouterId src_router, NocRouterId dst_router) const;
 
     /**
      * @brief Given a unique link identifier, get the corresponding link
@@ -376,7 +422,7 @@ class NocStorage {
 
     void set_device_grid_spec(int grid_width, int grid_height);
 
-    // general utiliy functions
+    // general utility functions
     /**
      * @brief The link is removed from the outgoing vector of links for
      * the source router. The link is not removed from the vector of all
@@ -404,6 +450,14 @@ class NocStorage {
      * NoC (routers and links cannot be added or removed). This function
      * should be called after building the NoC. Guarantees that
      * no future changes can be made.
+     *
+     * When the NoC building is finished, this function checks whether
+     * all links and routers have the same bandwidth and latency.
+     * If some NoC elements have different latencies or bandwidths than
+     * others, a flag is set to indicate that the detailed NoC model should be
+     * used. In the detailed model, instead of associating a single latency or
+     * bandwidth value with all NoC routers or links, each NoC router or link
+     * has its specific value.
      * 
      */
     void finished_building_noc();
@@ -495,4 +549,18 @@ class NocStorage {
     void echo_noc(char* file_name) const;
 };
 
-#endif
+
+template <template<typename> class Container>
+const std::vector<std::reference_wrapper<const NocLink>>& NocStorage::get_noc_links(const Container<NocLinkId>& noc_link_ids) const {
+    returnable_noc_link_const_refs_.clear();
+
+    std::transform(noc_link_ids.begin(), noc_link_ids.end(), std::back_inserter(returnable_noc_link_const_refs_),
+                   [this](const NocLinkId lid) {
+                       return std::reference_wrapper<const NocLink>(this->get_single_noc_link(lid));
+                   });
+
+    return returnable_noc_link_const_refs_;
+}
+
+#endif
+

vpr/src/place/noc_place_utils.cpp

@@ -146,10 +146,7 @@ void find_affected_noc_routers_and_update_noc_costs(const t_pl_blocks_to_be_move
     }
 
     // Iterate over all affected links and calculate their new congestion cost and store it
-    for (const auto& link_id : affected_noc_links) {
-        // get the affected link
-        const auto& link = noc_ctx.noc_model.get_single_noc_link(link_id);
-
+    for (const NocLink& link : noc_ctx.noc_model.get_noc_links(affected_noc_links)) {
         // calculate the new congestion cost for the link and store it
         proposed_link_congestion_costs[link] = calculate_link_congestion_cost(link);
 
@@ -174,10 +171,7 @@ void commit_noc_costs() {
     }
 
     // Iterate over all the NoC links whose bandwidth utilization was affected by the proposed move
-    for(auto link_id : affected_noc_links) {
-        // get the affected link
-        const auto& link = noc_ctx.noc_model.get_single_noc_link(link_id);
-
+    for (const NocLink& link : noc_ctx.noc_model.get_noc_links(affected_noc_links)) {
         // commit the new link congestion cost
         link_congestion_costs[link] = proposed_link_congestion_costs[link];
 
@@ -494,7 +488,7 @@ int check_noc_placement_costs(const t_placer_costs& costs, double error_toleranc
     }
 
     // Iterate over all NoC links and accumulate congestion cost
-    for(const auto& link : temp_noc_link_storage) {
+    for (const auto& link : temp_noc_link_storage) {
         cost_check.congestion += calculate_link_congestion_cost(link);
     }
 
@@ -555,10 +549,9 @@ std::pair<double, double> calculate_traffic_flow_latency_cost(const std::vector<
 
     double noc_link_latency_component = 0.0;
     if (noc_model.get_detailed_link_latency()) {
-        for (auto noc_link_id : traffic_flow_route) {
-            const NocLink& noc_link = noc_model.get_single_noc_link(noc_link_id);
-            double noc_link_latency = noc_link.get_latency();
-            noc_link_latency_component += noc_link_latency;
+        for (const NocLink& link : noc_model.get_noc_links(traffic_flow_route)) {
+            double link_latency = link.get_latency();
+            noc_link_latency_component += link_latency;
         }
     } else {
         auto num_of_links_in_traffic_flow = (double)traffic_flow_route.size();
@@ -575,9 +568,8 @@ std::pair<double, double> calculate_traffic_flow_latency_cost(const std::vector<
         const NocRouter& source_noc_router = noc_model.get_single_noc_router(source_noc_router_id);
         noc_router_latency_component = source_noc_router.get_latency();
 
-        for (auto noc_link_id : traffic_flow_route) {
-            const NocLink& noc_link = noc_model.get_single_noc_link(noc_link_id);
-            const NocRouterId sink_router_id = noc_link.get_sink_router();
+        for (const NocLink& link : noc_model.get_noc_links(traffic_flow_route)) {
+            const NocRouterId sink_router_id = link.get_sink_router();
             const NocRouter& sink_router = noc_model.get_single_noc_router(sink_router_id);
             double noc_router_latency = sink_router.get_latency();
             noc_router_latency_component += noc_router_latency;