Clear up flag documentation and strange logic

Signed-off-by: Dusty DeWeese <[email protected]>

Author: HackerFoo

vpr/src/base/read_options.cpp

@@ -1986,9 +1986,10 @@ argparse::ArgumentParser create_arg_parser(std::string prog_name, t_options& arg
 
     route_timing_grp.add_argument<float>(args.router_high_fanout_max_slope, "--router_high_fanout_max_slope")
         .help(
-            "Maximum routing predictor slope where high fanout routing is enabled.\n"
-            " -1.0 is normal progress, 0 is no progress.")
-        .default_value("-0.5")
+            "Minimum routing progress where high fanout routing is enabled."
+            " This is a ratio of the actual congestion reduction to what is expected based in the history.\n"
+            " 1.0 is normal progress, 0 is no progress.")
+        .default_value("0.1")
         .show_in(argparse::ShowIn::HELP_ONLY);
 
     route_timing_grp.add_argument<e_router_lookahead, ParseRouterLookahead>(args.router_lookahead_type, "--router_lookahead")

vpr/src/route/route_timing.cpp

@@ -1223,7 +1223,7 @@ static bool timing_driven_route_sink(
     //We normally route high fanout nets by only adding spatially close-by routing to the heap (reduces run-time).
     //However, if the current sink is 'critical' from a timing perspective, we put the entire route tree back onto
     //the heap to ensure it has more flexibility to find the best path.
-    if (high_fanout && !sink_critical && !net_is_global && !net_is_clock && !(routing_predictor.get_slope() > router_opts.high_fanout_max_slope)) {
+    if (high_fanout && !sink_critical && !net_is_global && !net_is_clock && -routing_predictor.get_slope() > router_opts.high_fanout_max_slope) {
         std::tie(found_path, cheapest) = router.timing_driven_route_connection_from_route_tree_high_fanout(rt_root,
                                                                                                            sink_node,
                                                                                                            cost_params,