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RePlAce

RePlAce: Advancing Solution Quality and Routability Validation in Global Placement

Features:

  • Analytic and nonlinear placement algorithm. Solves electrostatic force equations using Nesterov's method. (link)
  • Verified with various commercial technologies and research enablements using OpenDB (7/14/16/28/45/55/65nm).
  • Verified deterministic solution generation with various compilers and OS.
  • Supports Mixed-size placement mode.
Visualized examples from ISPD 2006 contest; adaptec2.inf Real-world Design: Coyote (TSMC16 7.5T)

Commands

global_placement
    [-timing_driven]
    [-routability_driven]
    [-skip_initial_place]
    [-incremental]
    [-bin_grid_count grid_count]
    [-density target_density]
    [-init_density_penalty init_density_penalty]
    [-init_wirelength_coef init_wirelength_coef]
    [-min_phi_coef min_phi_conef]
    [-max_phi_coef max_phi_coef]
    [-overflow overflow]
    [-initial_place_max_iter initial_place_max_iter]
    [-initial_place_max_fanout initial_place_max_fanout]
    [-routability_check_overflow routability_check_overflow]
    [-routability_max_density routability_max_density]
    [-routability_max_bloat_iter routability_max_bloat_iter]
    [-routability_max_inflation_iter routability_max_inflation_iter]
    [-routability_target_rc_metric routability_target_rc_metric]
    [-routability_inflation_ratio_coef routability_inflation_ratio_coef]
    [-routability_pitch_scale routability_pitch_scale]
    [-routability_max_inflation_ratio routability_max_inflation_ratio]
    [-routability_rc_coefficients routability_rc_coefficients]
    [-timing_driven_net_reweight_overflow]
    [-timing_driven_net_weight_max]
    [-timing_driven_nets_percentage]
    [-pad_left pad_left]
    [-pad_right pad_right]
    [-verbose_level level]
    [-force_cpu]

Tuning Parameters

  • -timing_driven: Enable timing-driven mode
  • -routability_driven: Enable routability-driven mode
  • -skip_initial_place : Skip the initial placement (BiCGSTAB solving) before Nesterov placement. IP improves HPWL by ~5% on large designs. Equal to '-initial_place_max_iter 0'
  • -incremental : Enable the incremental global placement. Users would need to tune other parameters (e.g., init_density_penalty) with pre-placed solutions.
  • -bin_grid_count: set bin grid's counts. Default value is defined by internal heuristic. Allowed values are [64,128,256,512,..., int].
  • -density: set target density. Default value is 0.70. Allowed values are [0-1, float].
  • -init_density_penalty: set initial density penalty. Default value is 8e-5. Allowed values are [1e-6 - 1e6, float].
  • -init_wirelength_coef: set initial wirelength coefficient. Default value is 0.25. Allowed values are [unlimited, float].
  • -min_phi_coef: set pcof_min(µ_k Lower Bound). Default value is 0.95. Allowed values are [0.95-1.05, float].
  • -max_phi_coef: set pcof_max(µ_k Upper Bound). Default value is 1.05. Allowed values are [1.00-1.20, float].
  • -overflow: set target overflow for termination condition. Default value is 0.1. Allowed values are [0-1, float].
  • -initial_place_max_iter: set maximum iterations in initial place. Default value is 20. Allowed values are [0-MAX_INT, int].
  • -initial_place_max_fanout: set net escape condition in initial place when 'fanout >= initial_place_max_fanout'. Default value is 200. Allowed values are [1-MAX_INT, int].
  • -timing_driven_net_reweight_overflow: set overflow threshold for timing-driven net reweighting. Allowed values are tcl list of [0-100, int].
  • -timing_driven_net_weight_max: Set the multiplier for the most timing critical nets. Default value is 1.9.
  • -timing_driven_nets_percentage: Set the percentage of nets that are reweighted in timing-driven mode. Default value is 10. Allowed values are [0-100, float]
  • -verbose_level: set verbose level for RePlAce. Default value is 1. Allowed values are [0-5, int].
  • -force_cpu: Force to use the CPU solver even if the GPU is available.

-timing_driven does a virtual repair_design to find slacks and weight nets with low slack. It adjusts the worst slacks (10% by default, modified with -timing_driven_nets_percentage) using a multiplier (1.9 by default, modified with -timing_driven_net_weight_max). The multiplier is scaled from the full value for the worst slack, to 1.0 at the timing_driven_nets_percentage point. Use the set_wire_rc command to set resistance and capacitance of estimated wires used for timing.

Example scripts

Regression tests

Limitations

Using the Python interface to gpl

This api tries to stay close to the api defined in C++ class Replace that is located in gpl/include/gpl/Replace.h

When initializing a design, a sequence of Python commands might look like the following:

from openroad import Design, Tech
tech = Tech()
tech.readLef(...)
design = Design(tech)
design.readDef(...)
gpl = design.getReplace()

Here is an example of some options / configurations to the global placer. (See Replace.h for a complete list)

gpl.setInitialPlaceMaxIter(iter)
gpl.setSkipIoMode(skip_io)
gpl.setTimingDrivenMode(timing_driven)
gpl.setTimingNetWeightMax(weight)

There are some useful Python functions located in the file grt/test/grt_aux.py but these are not considered a part of the (final) api and they may change.

FAQs

Check out GitHub discussion about this tool.

External references

  • C.-K. Cheng, A. B. Kahng, I. Kang and L. Wang, "RePlAce: Advancing Solution Quality and Routability Validation in Global Placement", IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 38(9) (2019), pp. 1717-1730.

  • J. Lu, P. Chen, C.-C. Chang, L. Sha, D. J.-H. Huang, C.-C. Teng and C.-K. Cheng, "ePlace: Electrostatics based Placement using Fast Fourier Transform and Nesterov's Method", ACM TODAES 20(2) (2015), article 17.

  • J. Lu, H. Zhuang, P. Chen, H. Chang, C.-C. Chang, Y.-C. Wong, L. Sha, D. J.-H. Huang, Y. Luo, C.-C. Teng and C.-K. Cheng, "ePlace-MS: Electrostatics based Placement for Mixed-Size Circuits", IEEE TCAD 34(5) (2015), pp. 685-698.

  • The timing-driven mode has been implemented by Mingyu Woo (only available in legacy repo in standalone branch.)

  • The routability-driven mode has been implemented by Mingyu Woo.

  • Timing-driven mode re-implementation is ongoing with the current clean-code structure.

Authors

  • Authors/maintainer since Jan 2020: Mingyu Woo (Ph.D. Advisor: Andrew. B. Kahng)
  • Original open-sourcing of RePlAce: August 2018, by Ilgweon Kang (Ph.D. Advisor: Chung-Kuan Cheng), Lutong Wang (Ph.D. Advisor: Andrew B. Kahng), and Mingyu Woo (Ph.D. Advisor: Andrew B. Kahng).
  • Also thanks to Dr. Jingwei Lu for open-sourcing the previous ePlace-MS/ePlace project code.

License

BSD 3-Clause License. See LICENSE file.