  Modern FPGAs continue to increase in capacity which requires more memory to
run the CAD flow. The routing resource graph, which is needed by the detailed
router, is a memory hungry data structure which describes all of the physical
resources and programmable connections within an FPGA. We propose a compression
scheme to reduce the memory requirements of the routing resource graph. The
scheme is simple to apply and requires only trivial changes to the FPGA
detailed routing algorithm. The approach does not require any assumptions about
the FPGA routing architecture. Numerical results show excellent compression (as
much as 3.6X overall memory reduction) with only a slight increase (~20% on
average) on the router runtime as a consequence of the routing graph
compression.
