the vtr design flow usually consists of three main component applications: odin ii which compiles verilog code to a circuit in berkeley logic interchange format (blif), a human-readable graph representation of the circuit; abc which optimizes the blif circuit produced by odin ii; and vpr which packs, places and routes the optimized circuit on the given fpga architecture. there are some additional optional tools that can process the vtr output further. for example, the fasm fpga assembly tool can produce programming bitstreams for some commercial fpgas (xilinx artix and lattice ice40) at the end of the vtr flow, while the openfpga tool integrates with vtr to produce a standard cell layout of a novel (proposed) fpga. it is also possible to use different tools for the first (hdl synthesis) stage of the vtr flow; for example the titan flow uses quartus to perform the hdl to logic synthesis stage, and then vpr to perform placement and routing.