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Compare2Files.bat: A Windows Script for Comparing Two Files

IC designers often need to compare and find small differences between two GDSII files -- typically one file is a slight revision of another file and they want to examine all the deltas on a layer by layer basis.

To do this, one can use Qckbool's XOR engine. The XOR operator generates the difference between two polygons or collections of polygons. If both inputs are identical then the output of XOR is empty. Anything that you do see in an XOR output is the difference.

  two similar files are compared (layer by layer) and the resulting output is a difference file

Compare2Files.bat

The script, Compare2Files.bat, uses the Qckbool XOR engine and the gdsfilt engine to compare two GDSII files layer by layer. Certain assumptions are made:

  • Each GDSII file has only a single top level structure.

  • We are comparing the same layers in File 1 as in File 2 - i.e. layer 5 to layer 5 and so on.

  • The differences between the data in the two files is relatively small. This is also a valid assumption for revisions of the same design.


Since the xor engine only works on layers within a single GDSII file, we do the following:

    Use gdsfilt to shift all the layers in one file by a known value - say by 200. So layer 5 in file 1 becomes layer 205.

    Merge the "shifted" file1 with file 2. Because we shifted the layers there is no collision of polygons on any given layer.

    run the xor engine on the merged file and output a new file with any differences.



Example 1 - Comparing two files

Here is how the batch file looks like...

rem define a variable for the path to the qckbool engine and gdsfilt engine
set BINDIR=c:\wcad\qckbool

rem define variables for the two input files
set file1=iss.gds
set file2=pad_mod.gds

Rem Shift the layer set in file 1 by 200. Output goes to shifted.sf
%BINDIR%\gdsfilte %file1% shifted.sf = -lyr0-200:200-400 -unixcmdline
erase *.log

rem Combine shifted.sf and file 2 - Output to xor_input.gds
%BINDIR%\gdsfilte shifted.sf xor_input.gds = -unixcmdline -add %file2% -combine xor_input =
erase *.log
erase shifted.sf

rem Perform xor, giving the hint that the layer sets are differ by 200. 
rem The output goes to xor_output.gds where the output data 
rem is shifted by 400 from the original set. Note: We selected to run with 2 threads.
%BINDIR%\newxor xor_input.gds xor_output.gds xor_input = x -output_layer_offset:400 -input_layer_offset:200 +nclip:1,100 -postunion  -thrnum:2

rem Last step is optional: Combine xor_input.gds and xor_output.gds and put the combined data in delta.gds. 
rem This provides a nice way to look at the XOR result. 
rem It would be sufficient to combine the XOR output with only one of the input files.
%BINDIR%\gdsfilte xor_input.gds delta.gds = -unixcmdline -add xor_output.gds -combine xor_input =
erase xor_input.log
erase xor_input.gds

erase *.ssn


Example 2 - Comparing two files with xy offset

This example compares layers 1 and 2 in two different files.
The prep'd files are pruned for layers 1 and 2 only.
The second file is offset against the first by 10,5 microns.

Here is how the batch file looks like...

rem Path to Qckbool engine.
set BINDIR=c:\wcad\qckbool

rem Input files..
set file1=iss.gds
set file2=pad_mod.gds

rem Shift the layer set in file 1 by 200. Output goes to shifted.sf. Include layers 1 and 2. Prune extraneous cells. 
%BINDIR%\gdsfilte %file1% shifted.sf = -lyr0-200:200-400 -unixcmdline -i1,2 -prune
erase *.log

rem Output goes to f2.sf. Include layers 1 and 2. Prune extraneous cells.
%BINDIR%\gdsfilte %file2% f2.sf = -unixcmdline -i1,2 -prune
erase *.log

rem Combine shifted.sf and file 2 - Output to xor_input.gds. Shifted.sf os offset 0,0 while f2.sf is shifted 10,5
%BINDIR%\gdsfilte shifted.sf xor_input.gds = -unixcmdline -add f2.sf -combine xor_input = -offset 0,0 10,5
erase *.log
erase shifted.sf f2.sf

rem Perform xor, giving the hint that the layer sets are differ by 200. 
rem The output goes to xor_output.gds where the output data 
rem is shifted by 400 from the original set. Note: We selected to run with 2 threads. Use boolw32f instead of newxor.
%BINDIR%\boolw32f xor_input.gds xor_output.gds xor_input 401;402 +1x201;+2x202  +nclip:1,100 -postunion  -thrnum:2

rem Last step is optional: Combine xor_input.gds and xor_output.gds and put the combined data in delta.gds. 
rem This provides a nice way to look at the XOR result. 
rem It would be sufficient to combine the XOR output with only one of the input files.
%BINDIR%\gdsfilte xor_input.gds delta.gds = -unixcmdline -add xor_output.gds -combine xor_input =
erase xor_input.log
erase xor_input.gds

erase *.ssn







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