GerryChain.jl
aka
motivation
neato: julia "feels like python, runs like C"
SHAPEFILE_PATH = "./PA_VTD.json"
POPULATION_COL = "TOT_POP"
ASSIGNMENT_COL = "538GOP_PL"
# Initialize graph and partition
graph = BaseGraph(SHAPEFILE_PATH, POPULATION_COL, ASSIGNMENT_COL)
partition = Partition(graph, ASSIGNMENT_COL)
# Define parameters of chain (number of steps and population constraint)
pop_constraint = PopulationConstraint(graph, POPULATION_COL, 0.02)
num_steps = 10
# Initialize Election of interest
election = Election("SEN10", ["SEN10D", "SEN10R"], graph.num_dists)
# Define election-related metrics and scores
election_metrics = [
vote_count("count_d", election, "SEN10D"),
efficiency_gap("efficiency_gap", election, "SEN10D"),
seats_won("seats_won", election, "SEN10D"),
mean_median("mean_median", election, "SEN10D")
]
scores = [
DistrictAggregate("presd", "PRES12D"),
ElectionTracker(election, election_metrics)
]
# Run the chain
println("Running 10-step ReCom chain...")
chain_data = recom_chain(graph, partition, pop_constraint, num_steps, scores)
# Get values of all scores at the 10th state of the chain
score_dict = get_scores_at_step(chain_data, 10)
# Get all vote counts for each state of the chain
vote_counts_arr = get_score_values(chain_data, "count_d")
running a chain in 34 lines of code!
where is our progress now?
- Most of core GerryChain is re-implemented in Julia! 🎊
- Some new features! ✨
- Package uploaded to Julia registry! 📦
-
using Pkg; Pkg.add("GerryChain")
-
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1
some differences w/ gerrychain...
- "updaters" are now "scores"
- Tallies âž¡ DistrictAggregate scores
- introduce district-level vs. plan-level scores
- saves time + memory
- acceptance functions must return a float in [0, 1] representing probability of acceptance rather than True or False
- forces user to think about what acceptance functions are for, reducing confusion w/ constraints!
- ReCom is first class in GerryChain.jl
- Python GerryChain very much built on the notion of "flips"
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new features! ✨
- built-in plotting 📊
- saving score values to CSV/json files 💾
- and of course, speed âš¡
The speed of GerryChain depends a lot on how it is configured
Population Constraint:Â Â Tighter the bounds âž¡ Longer times
Acceptance Probability: Lower probability  ➡ Longer times
Number of updaters:    More calculation   ➡ Longer times
Num steps:             More steps        ➡ Longer times
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Python Chain Times
Julia Chain Times
Julia and Python Chains, together
So currently we have a ~47x speedup in Julia over Python (over simple runs)
Up next... Parallelization
Up next... Parallelization
thank you!
leave us a 🌟 on github? 🥺👉👈
GerryChain.jl
By Matthew Sun
GerryChain.jl
- 415