Stratix 10 Flat Routing Error

[SamuelHo10]

Running VPR on a Stratix 10 architecture with flat routing enabled results in an error. I've tested that it works when flat routing is off.

$VTR_ROOT/vpr/vpr \
  $VTR_ROOT/vtr_flow/arch/titan/stratix10_arch.timing.xml \
  $VTR_ROOT/vtr_flow/benchmarks/blif/2/bw.blif \
  --flat_routing on \
  --route_chan_width 100 \
  -j12

Error Message:

## Computing tile lookahead
terminate called after throwing an instance of 'std::out_of_range'
  what():  unordered_map::at
./vtr.sh: line 12: 2382004 Aborted                 (core dumped) $VTR_ROOT/vpr/vpr $VTR_ROOT/vtr_flow/arch/titan/stratix10_arch.timing.xml $VTR_ROOT/vtr_flow/benchmarks/blif/2/bw.blif --flat_routing on --route_chan_width 100 -j12