Seemingly inconsistent bin density on gpl debug mode

[gudeh]

Describe the bug

Some gpl bins without any instances have higher than zero density on gpl debug mode, which is unexpected.

The e-place paper mentions a local smoothness technique which could be the explanation for this behavior:

Although, we did not find the implementation of this smoothness on the gpl code.
This could be due to a drawing inconsistency on the gui also.

Expected Behavior

Bins without any instances inside should have a density of 0.

Environment

./etc/Env.sh 
[WARNING] Your current OpenROAD version is outdated.
It is recommened to pull the latest changes.
If problem persists, file a github issue with the re-producible test case.
kernel: Linux 6.8.0-1015-gcp
os: Ubuntu 22.04.5 LTS (Jammy Jellyfish)
cmake version 3.24.2
-- The CXX compiler identification is GNU 11.4.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- OpenROAD version: v2.0-17668-gd629eed8f
-- System name: Linux
-- Compiler: GNU 11.4.0
-- Build type: RELEASE
-- Install prefix: /usr/local
-- C++ Standard: 17
-- C++ Standard Required: ON
-- C++ Extensions: OFF
-- The C compiler identification is GNU 11.4.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Performing Test C_COMPILER_SUPPORTS__-Wall
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-- Performing Test CXX_COMPILER_SUPPORTS__-Wall
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-- Performing Test C_COMPILER_SUPPORTS__-Wno-array-bounds
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-- Performing Test C_COMPILER_SUPPORTS__-Wno-maybe-uninitialized
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-- Performing Test CXX_COMPILER_SUPPORTS__-Wno-maybe-uninitialized
-- Performing Test CXX_COMPILER_SUPPORTS__-Wno-maybe-uninitialized - Success
-- Performing Test C_COMPILER_SUPPORTS__-Wno-format-overflow
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-- Performing Test C_COMPILER_SUPPORTS__-Wno-c++11-narrowing
-- Performing Test C_COMPILER_SUPPORTS__-Wno-c++11-narrowing - Failed
-- Performing Test CXX_COMPILER_SUPPORTS__-Wno-c++11-narrowing
-- Performing Test CXX_COMPILER_SUPPORTS__-Wno-c++11-narrowing - Failed
-- Performing Test C_COMPILER_SUPPORTS__-Wno-register
-- Performing Test C_COMPILER_SUPPORTS__-Wno-register - Failed
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-- Performing Test C_COMPILER_SUPPORTS__-Wno-format
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-- Performing Test C_COMPILER_SUPPORTS__-Wno-reserved-user-defined-literal
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-- Performing Test CXX_COMPILER_SUPPORTS__-Wno-reserved-user-defined-literal
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-- Performing Test C_COMPILER_SUPPORTS__-fpermissive
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-- Performing Test C_COMPILER_SUPPORTS__-x
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-- Performing Test CXX_COMPILER_SUPPORTS__-x
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-- Performing Test C_COMPILER_SUPPORTS__c++
-- Performing Test C_COMPILER_SUPPORTS__c++ - Failed
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-- Performing Test C_COMPILER_SUPPORTS__-std=c++17
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-- Performing Test CXX_COMPILER_SUPPORTS__-std=c++17
-- Performing Test CXX_COMPILER_SUPPORTS__-std=c++17 - Success
-- Performing Test C_COMPILER_SUPPORTS__-Wno-unused-but-set-variable
-- Performing Test C_COMPILER_SUPPORTS__-Wno-unused-but-set-variable - Success
-- Performing Test CXX_COMPILER_SUPPORTS__-Wno-unused-but-set-variable
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-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- TCL readline library: /usr/lib/x86_64-linux-gnu/libtclreadline.so
-- TCL readline header: /usr/include/x86_64-linux-gnu
-- Found SWIG: /usr/local/bin/swig (found suitable version "4.1.0", minimum required is "4.0")  
-- Using SWIG >= 4.1.0 -flatstaticmethod flag for python
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0")  
-- boost: 1.80.0
-- Found GTest: /usr/local/lib/cmake/GTest/GTestConfig.cmake (found version "1.13.0")  
-- GTest: 1.13.0
-- Found Python3: /usr/include/python3.10 (found version "3.10.12") found components: Development Development.Module Development.Embed 
-- Found ZLIB: /usr/lib/x86_64-linux-gnu/libz.so (found version "1.2.11") 
-- Found Threads: TRUE  
-- spdlog: 1.8.1
-- Found BISON: /usr/bin/bison (found version "3.8.2") 
-- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE) 
-- STA version: 2.6.0
-- STA git sha: aa598a2f14c5c142e90391a69988523505e7db3d
-- System name: Linux
-- Compiler: GNU 11.4.0
-- Build type: RELEASE
-- Build CXX_FLAGS: -O3 -DNDEBUG
-- Install prefix: /usr/local
-- Found FLEX: /usr/bin/flex (found version "2.6.4") 
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- TCL readline library: /usr/lib/x86_64-linux-gnu/libtclreadline.so
-- TCL readline header: /usr/include/x86_64-linux-gnu/tclreadline.h
-- CUDD library: /usr/local/lib/libcudd.a
-- CUDD header: /usr/local/include/cudd.h
-- SSTA: 0
-- Found SWIG: /usr/local/bin/swig (found suitable version "4.1.0", minimum required is "3.0")  
-- STA executable: /home/gudeh/masterCode/tools/OpenROAD/src/sta/app/sta
-- Found re2: /opt/or-tools/lib/cmake/re2/re2Config.cmake (found version "11.0.0") 
-- Found Clp: /opt/or-tools/lib/cmake/Clp/ClpConfig.cmake (found version "1.17.7") 
-- Found Cbc: /opt/or-tools/lib/cmake/Cbc/CbcConfig.cmake (found version "2.10.7") 
-- Found SCIP: /opt/or-tools/lib/cmake/scip/scip-config.cmake (found version "9.0.0") 
-- Found OpenMP_CXX: -fopenmp (found version "4.5") 
-- Found OpenMP: TRUE (found version "4.5")  
-- Found OR-Tools: /opt/or-tools/lib/cmake/ortools (version: 9.10.4067)
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- Found OpenMP_C: -fopenmp (found version "4.5") 
-- Found OpenMP: TRUE (found version "4.5")  
-- Found OpenMP: TRUE (found version "4.5")  
-- GUI is enabled
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0") found components: serialization 
-- Could NOT find VTune (missing: VTune_LIBRARIES VTune_INCLUDE_DIRS) 
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found suitable version "1.80.0", minimum required is "1.78")  
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0") found components: serialization system thread 
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0")  
-- Found Eigen3: /usr/local/share/eigen3/cmake/Eigen3Config.cmake (found version "3.4.1") 
-- TCL readline enabled
-- Tcl Extended disabled
-- Python3 enabled
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/tmp.hYuOR2VMMu

To Reproduce

Run gpl with debug mode and activate the density heatmap for bins.

Relevant log output

No response

Screenshots

No response

Additional Context

No response

[maliberty]

I believe the smoothing is implemented by changing the cell size (a bit different the how the paper describes the process but equivalent). However the smoothing seems too small to account for all the extra area.