How do you check consistency across all input files?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Validate relationships between files, not just each file independently. Names, units, revisions, physical technology, library models, and operating assumptions must describe the same intended design.
Technical Explanation
Start with identity: top module, hierarchy, netlist revision, macro configuration, library release, and process/metal stack. Then compare interfaces: cell and pin names, port widths, power-pin expectations, and the objects selected by SDC and UPF. A valid SDC aimed at old port names can leave the new design underconstrained. Check physical consistency through database scale, LEF/DEF units, sites, rows, tracks, layers, vias, and macro dimensions. Check electrical consistency through library units, voltage/temperature coverage, RC models, layer mapping, and the scenario assignments. Do not fix a unit mismatch by multiplying arbitrary constraint values until the reports look familiar. Finally compare reported design statistics and coverage with upstream expectations: instances, ports, unresolved references, clocks, macro count, scan annotation, and power-domain membership. Record differences and their explanations. Checksums help detect changed files, while reports prove what the tool interpreted. Both are needed because the correct file can be loaded in the wrong context.
Common Mistake
Accepting a package solely because all filenames share the same date or because there are no fatal parser errors.
Follow-up Question & Model Response
Which mismatch is hardest to notice? A plausible but wrong model or constraint can produce believable reports; cross-file manifests and coverage checks expose it.
Practical Example
A DEF uses 1000 units per micrometer, so a coordinate of 100000 represents 100 micrometers. Misinterpreting that number as micrometers creates a thousandfold error. Inspect the declared unit system and import result rather than guessing scale from large numbers.
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