Merge pull request #2523 from verilog-to-routing/pres_fac_max

Set the maximum pres_fac

Author: vaughnbetz

doc/src/vpr/command_line_usage.rst

@@ -1163,6 +1163,14 @@ VPR uses a negotiated congestion algorithm (based on Pathfinder) to perform rout
 
     **Default:** ``1.3``
 
+.. option:: --max_pres_fac <float>
+
+    Sets the maximum present overuse penalty factor that can ever result during routing. Should always be less than 1e25 or so to prevent overflow. 
+    Smaller values may help prevent circuitous routing in difficult routing problems, but may increase 
+    the number of routing iterations needed and hence runtime.
+
+    **Default:** ``1000.0``
+
 .. option:: --acc_fac <float>
 
     Specifies the accumulated overuse factor (historical congestion cost factor).

vpr/src/base/SetupVPR.cpp

@@ -423,6 +423,7 @@ static void SetupRouterOpts(const t_options& Options, t_router_opts* RouterOpts)
     RouterOpts->min_incremental_reroute_fanout = Options.min_incremental_reroute_fanout;
     RouterOpts->incr_reroute_delay_ripup = Options.incr_reroute_delay_ripup;
     RouterOpts->pres_fac_mult = Options.pres_fac_mult;
+    RouterOpts->max_pres_fac = Options.max_pres_fac;
     RouterOpts->route_type = Options.RouteType;
 
     RouterOpts->full_stats = Options.full_stats;

vpr/src/base/ShowSetup.cpp

@@ -328,6 +328,7 @@ static void ShowRouterOpts(const t_router_opts& RouterOpts) {
         VTR_LOG("RouterOpts.first_iter_pres_fac: %f\n", RouterOpts.first_iter_pres_fac);
         VTR_LOG("RouterOpts.initial_pres_fac: %f\n", RouterOpts.initial_pres_fac);
         VTR_LOG("RouterOpts.pres_fac_mult: %f\n", RouterOpts.pres_fac_mult);
+        VTR_LOG("RouterOpts.max_pres_fac: %f\n", RouterOpts.max_pres_fac);
         VTR_LOG("RouterOpts.max_router_iterations: %d\n", RouterOpts.max_router_iterations);
         VTR_LOG("RouterOpts.min_incremental_reroute_fanout: %d\n", RouterOpts.min_incremental_reroute_fanout);
         VTR_LOG("RouterOpts.do_check_rr_graph: %s\n", RouterOpts.do_check_rr_graph ? "true" : "false");
@@ -473,6 +474,7 @@ static void ShowRouterOpts(const t_router_opts& RouterOpts) {
         VTR_LOG("RouterOpts.first_iter_pres_fac: %f\n", RouterOpts.first_iter_pres_fac);
         VTR_LOG("RouterOpts.initial_pres_fac: %f\n", RouterOpts.initial_pres_fac);
         VTR_LOG("RouterOpts.pres_fac_mult: %f\n", RouterOpts.pres_fac_mult);
+        VTR_LOG("RouterOpts.max_pres_fac: %f\n", RouterOpts.max_pres_fac);
         VTR_LOG("RouterOpts.max_router_iterations: %d\n", RouterOpts.max_router_iterations);
         VTR_LOG("RouterOpts.min_incremental_reroute_fanout: %d\n", RouterOpts.min_incremental_reroute_fanout);
         VTR_LOG("RouterOpts.do_check_rr_graph: %s\n", RouterOpts.do_check_rr_graph ? "true" : "false");

vpr/src/base/read_options.cpp

@@ -2333,6 +2333,11 @@ argparse::ArgumentParser create_arg_parser(const std::string& prog_name, t_optio
         .default_value("1.3")
         .show_in(argparse::ShowIn::HELP_ONLY);
 
+    route_grp.add_argument(args.max_pres_fac, "-max_pres_fac")
+        .help("Sets the maximum present overuse penalty factor")
+        .default_value("1000.0")
+        .show_in(argparse::ShowIn::HELP_ONLY);
+
     route_grp.add_argument(args.acc_fac, "--acc_fac")
         .help("Specifies the accumulated overuse factor (historical congestion cost factor)")
         .default_value("1.0")

vpr/src/base/read_options.h

@@ -187,6 +187,7 @@ struct t_options {
     argparse::ArgValue<float> first_iter_pres_fac;
     argparse::ArgValue<float> initial_pres_fac;
     argparse::ArgValue<float> pres_fac_mult;
+    argparse::ArgValue<float> max_pres_fac;
     argparse::ArgValue<float> acc_fac;
     argparse::ArgValue<int> bb_factor;
     argparse::ArgValue<e_base_cost_type> base_cost_type;

vpr/src/base/vpr_types.h

@@ -1405,6 +1405,7 @@ struct t_router_opts {
     float first_iter_pres_fac;
     float initial_pres_fac;
     float pres_fac_mult;
+    float max_pres_fac;
     float acc_fac;
     float bend_cost;
     int max_router_iterations;

vpr/src/place/place.cpp

@@ -1709,8 +1709,8 @@ static e_move_result try_swap(const t_annealing_state* state,
     if (manual_move_enabled) {
 #ifndef NO_GRAPHICS
         create_move_outcome = manual_move_display_and_propose(manual_move_generator, blocks_affected, proposed_action.move_type, rlim, placer_opts, criticalities);
-#else //NO_GRAPHICS
-        // Cast to void to explicitly avoid warning.
+#else  //NO_GRAPHICS 
+        //Cast to void to explicitly avoid warning.
         (void)manual_move_generator;
 #endif //NO_GRAPHICS
     } else if (router_block_move) {

vpr/src/route/route.cpp

@@ -155,7 +155,8 @@ bool route(const Netlist<>& net_list,
     VTR_ASSERT(router_lookahead != nullptr);
 
     /* Routing parameters */
-    float pres_fac = update_draw_pres_fac(router_opts.first_iter_pres_fac); /* Typically 0 -> ignore cong. */
+    float pres_fac = router_opts.first_iter_pres_fac;
+    update_draw_pres_fac(pres_fac); /* Typically 0 -> ignore cong. */
     int bb_fac = router_opts.bb_factor;
 
     /* When routing conflicts are detected the bounding boxes are scaled
@@ -357,7 +358,8 @@ bool route(const Netlist<>& net_list,
             //Decrease pres_fac so that critical connections will take more direct routes
             //Note that we use first_iter_pres_fac here (typically zero), and switch to
             //use initial_pres_fac on the next iteration.
-            pres_fac = update_draw_pres_fac(router_opts.first_iter_pres_fac);
+            pres_fac = router_opts.first_iter_pres_fac;
+            update_draw_pres_fac(pres_fac);
 
             //Reduce timing tolerances to re-route more delay-suboptimal signals
             connections_inf.set_connection_criticality_tolerance(0.7);
@@ -374,7 +376,8 @@ bool route(const Netlist<>& net_list,
             //after the first routing convergence. Since that is often zero,
             //we want to set pres_fac to a reasonable (i.e. typically non-zero)
             //value afterwards -- so it grows when multiplied by pres_fac_mult
-            pres_fac = update_draw_pres_fac(router_opts.initial_pres_fac);
+            pres_fac = router_opts.initial_pres_fac;
+            update_draw_pres_fac(pres_fac);
         }
 
         //Have we converged the maximum number of times, did not make any changes, or does it seem
@@ -437,12 +440,13 @@ bool route(const Netlist<>& net_list,
 
         //Update pres_fac
         if (itry == 1) {
-            pres_fac = update_draw_pres_fac(router_opts.initial_pres_fac);
+            pres_fac = router_opts.initial_pres_fac;
+            update_draw_pres_fac(pres_fac);
         } else {
             pres_fac *= router_opts.pres_fac_mult;
-
-            /* Avoid overflow for high iteration counts, even if acc_cost is big */
-            pres_fac = update_draw_pres_fac(std::min(pres_fac, static_cast<float>(HUGE_POSITIVE_FLOAT / 1e5)));
+            pres_fac = std::min(pres_fac, router_opts.max_pres_fac);
+            /* Set the maximum pres_fac to the value passed by the command line argument */
+            update_draw_pres_fac(pres_fac);
 
             // Increase short path criticality if it's having a hard time resolving hold violations due to congestion
             if (budgeting_inf.if_set()) {

vpr/src/route/route_utils.cpp

@@ -507,15 +507,16 @@ void try_graph(int width_fac,
                     is_flat);
 }
 
-float update_draw_pres_fac(float new_pres_fac) {
 #ifndef NO_GRAPHICS
-
+void update_draw_pres_fac(const float new_pres_fac) {
+#else
+void update_draw_pres_fac(const float /*new_pres_fac*/) {
+#endif
+#ifndef NO_GRAPHICS
     // Only updates the drawing pres_fac if graphics is enabled
     get_draw_state_vars()->pres_fac = new_pres_fac;
 
 #endif // NO_GRAPHICS
-
-    return new_pres_fac;
 }
 
 #ifndef NO_GRAPHICS

vpr/src/route/route_utils.h

@@ -136,10 +136,8 @@ void try_graph(int width_fac,
                int num_directs,
                bool is_flat);
 
-/* This routine should take the new value of the present congestion factor
- * and propagate it to all the relevant data fields in the vpr flow.
- * Currently, it only updates the pres_fac used by the drawing functions */
-float update_draw_pres_fac(float new_pres_fac);
+/* This routine updates the pres_fac used by the drawing functions */
+void update_draw_pres_fac(const float new_pres_fac);
 
 #ifndef NO_GRAPHICS
 /** Updates router iteration information and checks for router iteration and net id breakpoints