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Electrical and Computer Engineering
Eric Rotenberg

CBP2025 Simulator Framework

Simulator

  • The simulator reads instructions from a trace in .gz format directly.
  • Each instruction from the trace may generate several “pieces”. The number of pieces depends on the number of 64-bit output values and the number of output registers. For instance :
    • A vector instruction that writes 128-bit registers will cause two pieces to be generated.
    • A scalar instruction that writes two general-purpose registers will cause two pieces to be generated.
    • A vector instruction that writes two 128-bit registers will cause four pieces to be generated.
    • A scalar load instruction with base update will produce two pieces: 1 load and 1 ALU for the base-register update.
  • The simulator schedules instructions according to register dependencies, memory dependencies (note: oracle memory disambiguation is modeled), instruction execution latencies, and structural constraints:
    • Window size
    • Superscalar width
    • Execution lanes
    • 3-level cache hierarchy
  • Contestants are provided with a hook to predict conditional branches.
  • All other branches are predicted perfectly.
  • The simulator reports instruction count, cycle count, conditional branch mispredictions, and other relevant measurements, both for the full simulation and post-warmup simulation
    • The first half of the simulation is considered warmup.
    • The second half is what’s used for measuring results.
  • Also see the README for more detailed information.

Training Traces

  • There are 105 training traces.
  • A trace is between 10 million and 130 million instructions.
  • To untar the traces: tar -xvf foo.tar.xz
  • Contestants may also download the traces using gdown:
    • pip install gdown
    • gdown –folder //drive.google.com/drive/folders/10CL13RGDW3zn-Dx7L0ineRvl7EpRsZDW
  • The CBP2025 organizers characterized data-dependent conditional branches in the training traces, which may inspire interesting directions for branch predictor design. Access the PDF file containing this characterization.