Large Skew between Identical Graph Outputs - 2025.2 English - UG1076

AI Engine Tools and Flows User Guide (UG1076)
Document ID
UG1076
Release Date
2025-11-20
Version
2025.2 English
If a design has multiple instantiations of the same graph, consider using the stamp and repeat flow in the mapper. This allows you to specify that all graphs are mapped in an identical manner in the area group region provided for each graph. This not only simplifies the problem for the mapper, it also significantly reduces skew between the outputs of different graphs. This is particularly important for wireless communications designs with multiple antennas. Steps to use the stamp and repeat flow are as follows:
  1. Define an area group for each graph. For example, in the following, add constraints in the aiecst file.
    "GlobalConstraints": {
  "areaGroup": {
    "name": "ant0_cores",
    "nodeGroup": ["tx_chain0.*"],
    "tileGroup": ["(0,0):(3,3)"]
  },
  "areaGroup": {
    "name": "ant1_cores",
    "nodeGroup": ["tx_chain1.*"],
    "tileGroup": ["(4,0):(7,3)"]
  }
}
    Alternatively, add constraints in the graph:
    location<graph>(tx_chain0) = bounding_box(0,0,3,3);
location<graph>(tx_chain1) = bounding_box(4,0,7,3);
  2. Define the stamp and repeat constraint in the aiecst file.
    {
  "GlobalConstraints": {
    "isomorphicGraphGroup": {
      "name": "isoGroup",
      "referenceGraph": "tx_chain0",
      "stampedGraphs": ["tx_chain1"]
    }
  }
}
    Note: You can apply additional constraints to the designated reference graph, such as co-location or absolute location constraints. These constraints automatically apply to other graphs with an appropriate offset.
    Note: For more information see Mapping Constraints in AI Engine Kernel and Graph Programming Guide (UG1079).