Debugging Aids


This section is only relevant to developers modifying VPR

To access detailed echo files from VPR’s operation, use the command-line option --echo_file on. After parsing the netlist and architecture files, VPR dumps out an image of its internal data structures into echo files (typically ending in .echo). These files can be examined to be sure that VPR is parsing the input files as you expect. The critical_path.echo file lists details about the critical path of a circuit, and is very useful for determining why your circuit is so fast or so slow.

If the preprocessor flag DEBUG is defined in vpr_types.h, some additional sanity checks are performed during a run. DEBUG only slows execution by 1 to 2%. The major sanity checks are always enabled, regardless of the state of DEBUG. Finally, if VERBOSE is set in vpr_types.h, a great deal of intermediate data will be printed to the screen as VPR runs. If you set verbose, you may want to redirect screen output to a file.

The initial and final placement costs provide useful numbers for regression testing the netlist parsers and the placer, respectively. VPR generates and prints out a routing serial number to allow easy regression testing of the router.

Finally, if you need to route an FPGA whose routing architecture cannot be described in VPR’s architecture description file, don’t despair! The router, graphics, sanity checker, and statistics routines all work only with a graph that defines all the available routing resources in the FPGA and the permissible connections between them. If you change the routines that build this graph (in rr_graph*.c) so that they create a graph describing your FPGA, you should be able to route your FPGA. If you want to read a text file describing the entire routing resource graph, call the dump_rr_graph subroutine.