Save Time When Reloading a Big GDSII File

If you regularly work with large GDSII files (say 5 GB to 50 GB) you know that opening such a file takes time. A lot of time. Enough time to get a coffee, drink it, refill it, check your email ... play a little on-line poker ...

There is not a whole lot that can be done about that - as you've seen in the previous sections, a lot of computation goes into opening a layout file. However if you are going to use the same GDSII file day after day (without modifying it) you can at least avoid repeating this long wait.

When opening a layout file QISLIB computes and loads into memory two essential tables describing the layout: a scan table and a quad tree table.

It is possible to have these two chunks of data stored to disk. The next time we reopen the same layout file, instead of recomputing the scan and quad data we load it directly from disk into memory. That load is very very fast as it is limited only by disk IO.