RRGraph Folding

This directory is used for storing / folding routing resource graphs using different folding methods.

Files / Directories

• flat_graphs/ is the directory where the folding scripts will look for the flat rr_graph.xml files
  • to save flat rr_graphs to this directory, run vpr with the argument

  --write_rr_graph /path/to/flat_graphs/your_graph.xml
  

  • for convenience, the rr_graph for architecture EArch.xml and circuit tseng.blif is already included in flat_graphs/
• folded_graphs/ is the directory where the folding scripts will save the folded rr_graph.xml files
  • to generate folded rr_graphs, follow the instructions below
• fold_rr_graph.py is the script that takes care of folding and saving rr_graphs from flat to folded

Generating Folded RR Graphs

• To generate a folded rr_graph, run fold_rr_graph.py with the following command

python fold_rr_graph.py <folding_method> <flat_graph_name>

• the <folding_method> argument refers to the folding method script in the folding_methods/ directory to be used for folding
• the <flat_graph_name> refers to the name of the flat graph in the flat_graphs directory that you wish to fold
• If you want to fold all the graphs in the flat_graphs directory, simply omit the <flat_graph_name> argument, and every flat graph will be folded.
• fold_rr_graph.py will execute in the following order
  1. Read flat rr_graph into memory from flat_graphs/<flat_graph_name>.xml
  2. Fold the flat rr_graph using the desired <folding_method>
  3. Save the folded rr_graph as <folding_method>_<flat_graph_name>.xml in the folded_graphs directory
  4. Print out folding metrics to the console including data such as nodes and edges % of original size.

Using Folded RR Graphs in VTR

• Currently the only working method to use a folded rr_graph in VTR requires that the folded graph is read from a file.
• This means that a custom rr_graph reader must be implemented for each folding method.
• Instructions on how to implement changes to the rr_graph reader can be found at $VTR_ROOT/vpr/src/route/SCHEMA_GENERATOR.md

Working Example

• Branches for each folding method follow the naming convention that the git branch name is the same as the folding method name.
• A working example of the nodes_all_attr folding method can be found on the nodes_all_attr branch
• To run this example, simply checkout the branch, build VTR and then run the following command

    $VTR_ROOT/vtr_flow/arch/timing/EArch.xml \
    $VTR_ROOT/vtr_flow/benchmarks/blif/tseng.blif \
    --route_chan_width 100 --read_rr_graph path/to/folded_graphs/nodes_all_attr_EArch_tseng.xml

• To compare with the flat graph, checkout this branch, build VTR and then run the following command

$VTR_ROOT/vtr_flow/arch/timing/EArch.xml \
    $VTR_ROOT/vtr_flow/benchmarks/blif/tseng.blif \
    --route_chan_width 100 --read_rr_graph path/to/flat_graphs/EArch_tseng.xml

Visual Representation of Folding Methods

Flat Representation

Nodes All Attributes Folding Method

Switches Subsets Folding Method

Dest Switch Subsets Folding Method

Quick Overview of Results