Module: Equalshares::Satisfaction

Defined in:
lib/equalshares/satisfaction.rb

Overview

Additive satisfaction measures for approval ballots, matching pabutools.

For the Method of Equal Shares, only the per-approver marginal utility u_i(c) of a project matters, and for these measures it is uniform across all approvers of c (it depends on c, not on i). This lets the fixed-budget loop stay unchanged in its payment mechanics (each project still has to raise its full cost, split as equally as possible) while the selection criterion becomes u(c) / maxPayment.

Cost_Sat        u(c) = cost(c)                 (equalshares.net default)
Cardinality_Sat u(c) = 1

Both are verified to match pabutools exactly (Cost_Sat and Cardinality_Sat). Each strategy returns the per-approver utility in the same numeric family as the cost passed in (Rational for exact mode, Float for float mode), so downstream arithmetic keeps its accuracy.

Constant Summary collapse

NAMES = 
%w[cost cardinality effort].freeze
COST =

Each measure is a callable per_voter(cost_c, num_approvers) -> Numeric.

->(cost_c, _n) { cost_c }
CARDINALITY = 
->(_cost_c, _n) { 1 }
EFFORT = 
->(cost_c, n) { cost_c / n }

Class Method Summary collapse

Class Method Details

.for(name) ⇒ Object 



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# File 'lib/equalshares/satisfaction.rb', line 24

def for(name)
  case name
  when "cost" then COST
  when "cardinality" then CARDINALITY
  when "effort" then EFFORT
  else
    raise ComputeError, "Unknown satisfaction measure: #{name} (allowed: #{NAMES.join(', ')})"
  end
end