Parasitic Backannotation Report

The Spectre FX log file displays the statistical data and status update related to parasitic file during parsing and annotation.

This can be explained with the following examples:

Example 1: Multiple Small SPF/DPF files

In the netlist, the SPF/DPF files are invoked using the following options:

.option sfx_ba_dspf_net=test.spf subckt=[inv_2x]
.option sfx_ba_dspf_instance=test.dpf subckt=[inv_2x]
.option sfx_ba_dspf_net=test_ver2.spf subckt=[inv_2x_ver2]
.option sfx_ba_dspf_instance=test_ver2.dpf subckt=[inv_2x_ver2]

In the log file, Spectre FX displays the updates related to the reading and backannotation of each pair of SPF/DPF files with the elapsed time, and also displays the combined statistical data related to the backannotation of all the files, as shown below.

Finished reading and back-annotating test.spf, test.dpf (00:00:00.011)
Finished reading and back-annotating test_ver2.spf, test_ver2.dpf (00:00:00.011)
DSPF Parsing Summary: (00:00:00.022)                                            
                Bytes parsed: 15633                                            
                Number nets: 10                                                 
                Number of elements: 264                                          
                       Number of MOSFETs: 24                                   
                       Number of resistors: 120                                
                       Number of capacitors: 120                              
                               Number of grounded capacitors: 82             
                               Number of coupled capacitors: 38                
                Number of shorted resistors: 8                              

Backannotation Summary: (00:00:00.000)
                Number of nets: 10 (100.0%)
                Number of elements: 264 (100.0%)
                        Number of MOSFETS: 24 (100.0%)
                        Number of resistors: 120 (100.0%)
                        Number of capacitors: 120 (100.0%)
                               Number of grounded capacitors: 82
                               Number of coupling capacitors: 38

Example 2: A 20GB DSPF File

In the netlist, no subcircuit or instance is specified for the DSPF file. As a result, the subcircuit definition in the DSPF file is used. To read both RC NET and Instance sections, use the following two options for the same DSPF file:

.option sfx_ba_dspf_net=./netlist/all.dspf
.option sfx_ba_dspf_instance=./netlist/all.dspf

In the log file, while parsing every 1GB file or backannotating every 10M elements, Spectre FX updates the following information to indicate the status:

Starting Hierarchical Netlist Creation ...
Starting DSPF parsing (./netlist/all.dspf)...
        1 GB parsed... 
        2 GB parsed.. 
        3 GB parsed... 
        ……
        19 GB parsed...              
Starting backannotation...
        10000000 elements backannotated...
        20000000 elements backnnotated...
        30000000 elements backannotated... 
        ……
        100000000 elements backannotated...


Finished reading and backannotating ./netlist/all.dspf (00:19:10.592)
DSPF Parsing Summary: (00:10:36.143) 
         Bytes parsed: 21130434084 
         Number of nets: 1304157 
         Number of elements: 108419360 
               Number of diodes: 426 
         Number of instances: 3532336 
         Number of resistors: 17484138 
         Number of capacitors: 87402460 
                       Number of grounded capacitors: 12017964 
                       Number of coupled capacitors: 75384496 
         Number of shorted resistors: 47                          

Backannotation Summary: (00:08:34.448)

        Number of nets: 1153843 (88.5%)
         Number of floating nets: 114763 (8.8%)
         Number of elements: 104189868 (96.1%) 
         Number of instances: 3532336 (100.0%)
                Number of resistors: 16787246 (96.0%)
                Number of capacitors: 83870286 (96.0%)
                        Number of grounded capacitors: 11594495
                        Number of coupling capacitors: 72275791

Time for Hierarchical Netlist Creation: CPU = 1.79657 ks (29m  56.6s), elapsed = 1.20154 ks (20m  1.5s).

Example 3: A Small DSPF File with Discarded Nets

The following example shows how the discarded nets are reported in the DSPF backannotation summary:

Finished reading and back-annotating test_discard.spf, test.dpf (00:00:00.007)
DSPF Parsing Summary: (00:00:00.007)
               Bytes parsed: 7767
               Number nets: 4
               Number discarded nets: 1
               Number elements: 103
                        Number MOSFETs: 12
                        Number resistors: 49
                        Number capacitors: 42
                                Number grounded capacitors: 28
                                 Number coupled capacitors: 14

Backannotation Summary: (00:00:00.000)
               Number nets: 4 (100.0%)
               Number elements: 96 (93.2%)
                         Number MOSFETS: 12 (100.0%)
                         Number resistors: 49 (100.0%)
                         Number capacitors: 35 (83.3%)
                               Number grounded capacitors: 28
                               Number coupling capacitors: 7

Spectre FX Circuit Simulator User Guide
Product Version 23.1, September 2023