Strange resistor network in placement parasitics #8408
Description
Describe the bug
In the SPEF file written out by estimate_parasitics -placement -spef_file <filename> for a 2-pin net I see the following:
*D_NET net74 0.138424
*CONN
*I _607_:A1 I *D NAND2_X4
*I place74:Z O *D BUF_X1
*CAP
1 net74:0 0.069212
2 net74:1 0.069212
*RES
1 net74:0 net74:0 1e-06
2 net74:0 place74:Z 1e-06
3 net74:0 place74:Z 1e-06
4 net74:0 place74:Z 1e-06
5 net74:1 net74:0 0.00556246
6 net74:1 _607_:A1 1e-06
7 net74:1 _607_:A1 1e-06
8 net74:0 place74:Z 1e-06
*END
There are duplicated (parallel) resistors. One group is
2 net74:0 place74:Z 1e-06
3 net74:0 place74:Z 1e-06
4 net74:0 place74:Z 1e-06
8 net74:0 place74:Z 1e-06
another is
6 net74:1 _607_:A1 1e-06
7 net74:1 _607_:A1 1e-06
There is also one resistor with its ends short-circuited:
1 net74:0 net74:0 1e-06
This was on nangate45/gcd but shows up on other PDKs too.
Expected Behavior
Resistive network with a tree topology
Environment
OR a5c4dfa7fbTo Reproduce
make DESIGN_CONFIG=./designs/nangate45/gcd/config.mk open_place
and then
estimate_parasitics -placement -spef_file placement.spef
Relevant log output
Screenshots
No response
Additional Context
No response