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Property List Comparison

The Per-Cell Objects mode allows properties to be compared, unlike the other modes. There are three classes of properties: structure (cell) properties, cell instance properties, and object properties.

Whether or not to check properties can be set independently for each type of object. Properties of a given object type will only be compared when enabled by checking the boxes in the Properties group, plus the Structure Properties check box. When not checked, the properties of the corresponding object, cell instance, or the structure, will be ignored.

Property lists of objects and instances are only compared between otherwise identical objects or instances. Cell structure property lists will be compared whether or not other differences are found, when enabled.

There are three filters that can be applied, to reduce the number of properties compared. These correspond to cell properties, instance properties, and object properties. Further, different filtering is applied when comparing electrical and physical mode data. The Property Filtering option menu and Setup button control the filtering applied.

The Default choice of the menu applies default filtering. With this choice, there is no filtering (all properties considered) when comparing physical mode data. In electrical mode, the following defaults are applied:

Cell properties
Compare only PARAM, VIRTUAL, NEWMUT, SYMBLC, and NODMAP properties.
Instance properties
Compare only MODEL, VALUE, PARAM, and NOPHYS properties.
Object properties
Ignore all electrical properties of objects.

This filtering limits the comparison to properties over which the user has control, and whose differences are likely to indicate an actual design difference.

The None choice of the menu effectively turns filtering off, for both electrical and physical modes. This is comprehensive, but for electrical mode a lot of the internal properties, for example NODE properties, will be flagged as differing but may not represent a true difference in the design as the strings may include arbitrary internal assignments for some parameters.

The third possible menu choice, Custom allows the user to completely specify the filtering behavior. This is described in the next section. The filtering is specified from the pop-up produced by pressing the Setup button.

Properties are compared by number and string. In the output file, property comparison result lines are all in comment form (with `#' as the first character) so that they will be ignored if the file is subsequently processed with the !diffcells command. Property comparison results consist of a string indicating the cell, instance, or object containing the properties. If an instance or object, this is common to both input sources. Following this are listings of properties found in one source and not the other. Properties that are identical in the two sources are not listed.

next up previous contents index
Next: Custom Property Filtering Up: The Compare Layouts Button: Previous: Comparison Mode Pages   Contents   Index
Stephen R. Whiteley 2022-05-28