[STA] Fixed Incremental Slack Timing Analysis Verify Code

In debug mode, the STA checks if the incremental STA matches the STA
computed from scratch. In this check it checked for if the critical
nodes matched; however, the nodes returned are not stably deterministic
(it does not break ties in a deterministic way). After discussing with
Vaughn, it is safe to just remove the nodes check since it would not
change the result of the analysis.

closes #2754

Author: AlexandreSinger

vpr/src/timing/slack_evaluation.cpp

@@ -436,33 +436,28 @@ bool SetupSlackCrit::verify_pin_criticalities(const tatum::TimingGraph& timing_g
 
 bool SetupSlackCrit::verify_max_req_worst_slack(const tatum::TimingGraph& timing_graph, const tatum::SetupTimingAnalyzer& analyzer) {
     auto calc_max_req = max_req_;
-    auto calc_max_req_node = max_req_node_;
-
     auto calc_worst_slack = worst_slack_;
-    auto calc_worst_slack_node = worst_slack_node_;
 
     recompute_max_req_and_worst_slack(timing_graph, analyzer);
 
+    // NOTE: We only check if the required time and the worst slack matches, we
+    //       do not check if the max required nodes or the worst slack nodes
+    //       match. This is because the incremental timing analysis and the non-
+    //       incremental timing analysis do not break ties deterministically,
+    //       so they may get different nodes; but they should always get the same
+    //       required time and worst slack. If the incremental timing analysis
+    //       gets different nodes, this will not change the results of the
+    //       timing analysis.
     if (calc_max_req != max_req_) {
         VPR_ERROR(VPR_ERROR_TIMING,
                   "Calculated max required times does not match value calculated from scratch");
         return false;
     }
-    if (calc_max_req_node != max_req_node_) {
-        VPR_ERROR(VPR_ERROR_TIMING,
-                  "Calculated max required nodes does not match value calculated from scratch");
-        return false;
-    }
     if (calc_worst_slack != worst_slack_) {
         VPR_ERROR(VPR_ERROR_TIMING,
                   "Calculated worst slack does not match value calculated from scratch");
         return false;
     }
-    if (calc_worst_slack_node != worst_slack_node_) {
-        VPR_ERROR(VPR_ERROR_TIMING,
-                  "Calculated worst slack nodes does not match value calculated from scratch");
-        return false;
-    }
 
     return true;
 }