How does record_layout_editing actually enable multiple engineers to work on parallel ECO changes to the same layout?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
record_layout_editing -start begins recording, and every layout-editing operation performed afterward (create/remove of layout objects via Tcl, set_attribute, and GUI move/resize) gets captured. record_layout_editing -stop -output <file> writes those recorded operations as a Tcl script. Multiple engineers can each record their own independent session this way, producing separate Tcl files that can ALL be applied to the original, unmodified layout -- rather than each engineer's changes needing to be applied sequentially to an already-modified copy.
Technical Explanation
- record_layout_editing -start begins recording; every layout-editing operation performed afterward -- create/remove of layout objects via Tcl, set_attribute, and even GUI move/resize actions -- gets captured.
- record_layout_editing -stop -output <file> writes the recorded operations as a standalone Tcl script.
- This lets MULTIPLE engineers each record their own independent editing session against the same starting layout, producing separate Tcl files.
- Those separate files can all be applied to the ORIGINAL, unmodified layout -- rather than requiring each engineer's changes to be applied sequentially to an already-modified copy, which would create ordering dependencies and merge conflicts.
What To Check
- Warning sign: two engineers' recorded ECO scripts, when both applied to the original layout, produce conflicting or overlapping changes to the same object.
- Inspect: review both recorded Tcl scripts for overlapping object references before applying both.
- Correct: resolve the conflict explicitly (coordinate which engineer's change takes precedence, or merge the intent manually) rather than applying both scripts and hoping the later one silently wins.
Command Checks & Actions
record_layout_editing -startBegins capturing every layout-editing operation performed from this point forward.
record_layout_editing -stop -output layout_changes1.tclStops recording and writes the captured operations as a standalone, independently-applicable Tcl script.
Healthy, Suspicious & Hard-stop Results
- Expected: each engineer's recorded script applies cleanly to the original layout with no object-level conflicts against other engineers' scripts.
- Investigate: two recorded scripts reference the same layout object -- worth reviewing before applying both, since the tool itself doesn't automatically resolve that kind of conflict.
- Stop: multiple engineers' recorded scripts are applied to the original layout without ever checking for overlapping object references between them.
Common Mistake
The Trap: Assuming parallel ECO changes from different engineers have to be applied sequentially to the same evolving layout (risking one engineer's change disrupting another's) -- record_layout_editing specifically avoids that by letting each recorded script apply independently to the original layout.
What The Interviewer Is Testing
Whether you understand record_layout_editing's actual value proposition (parallel, independently-applicable scripts against a shared original) rather than just knowing the -start/-stop syntax.
Practical Example
Debug Scenario: Two engineers each use record_layout_editing to make independent ECO fixes to different regions of the same design. Their two recorded Tcl scripts both apply cleanly to the original layout since they touched different, non-overlapping objects -- exactly the workflow record_layout_editing is built to support.
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