Performance slowdown while using pin in search

[icbenchpeng]

We found that hash lookup in SDC is extremely expensive. As OpenRoad is using iterm and bterm as pin, using pin to find instance is another expensive thing. So for OpenSTA the best practise is to store the SDC attributes on vertex as pin is not possible to store these information. So we'd better change the search structure using vertex to replace pins. And next step is to preamble sdc lookups into vertex structure, which means elab instance lookups on vertex.

[icbenchpeng]

Another issue is the arrival and required value cost by CRPR. We have seen case that cause 20Gb memory cost by resizing a cell in the network with CRPR on. Tag propagation will cause different CRPR tags going through different vertex and causing memory blow-up (the upper memory cost is about 160G with a small case). With this situation it is better to store such values on disk or use Sub Timing Graphs for such case. I'd prefer swap cold data on disk rather than Sub Timing Graph. And as the values are shared on disk, it is better to have a multi-mode solution across different process using current architecture.