Remove internal context
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avitex
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146
lib/glicko.ex
146
lib/glicko.ex
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@ -50,157 +50,149 @@ defmodule Glicko do
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|> Player.to_v1
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end
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defp do_new_rating({player_rating, player_rating_deviation, player_volatility}, [], _) do
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player_post_rating_deviation = calc_player_pre_rating_deviation(
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:math.pow(player_rating_deviation, 2),
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player_volatility
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)
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defp do_new_rating({player_r, player_pre_rd, player_v}, [], _) do
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player_post_rd = calc_player_post_base_rd(:math.pow(player_pre_rd, 2), player_v)
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{player_rating, player_post_rating_deviation, player_volatility}
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{player_r, player_post_rd, player_v}
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end
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defp do_new_rating({player_rating, player_rating_deviation, player_volatility}, results, opts) do
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ctx =
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Map.new
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|> Map.put(:system_constant, Keyword.get(opts, :system_constant, @default_system_constant))
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|> Map.put(:convergence_tolerance, Keyword.get(opts, :convergence_tolerance, @default_convergence_tolerance))
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|> Map.put(:player_rating, player_rating)
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|> Map.put(:player_volatility, player_volatility)
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|> Map.put(:player_rating_deviation, player_rating_deviation)
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|> Map.put(:player_rating_deviation_squared, :math.pow(player_rating_deviation, 2))
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defp do_new_rating({player_pre_r, player_pre_rd, player_pre_v}, results, opts) do
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sys_const = Keyword.get(opts, :system_constant, @default_system_constant)
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conv_tol = Keyword.get(opts, :convergence_tolerance, @default_convergence_tolerance)
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# Init
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ctx = Map.put(ctx, :results, Enum.map(results, &build_internal_result(ctx, &1)))
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ctx = Map.put(ctx, :results_effect, calc_results_effect(ctx))
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player_pre_rd_sq = :math.pow(player_pre_rd, 2)
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results = Enum.map(results, &build_internal_result(player_pre_r, &1))
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results_effect = calc_results_effect(results)
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# Step 3
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ctx = Map.put(ctx, :variance_estimate, calc_variance_estimate(ctx))
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variance_est = calc_variance_estimate(results)
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# Step 4
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ctx = Map.put(ctx, :delta, calc_delta(ctx))
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delta = calc_delta(results_effect, variance_est)
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# Step 5.1
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ctx = Map.put(ctx, :alpha, calc_alpha(ctx))
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alpha = calc_alpha(player_pre_v)
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# Step 5.2
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{initial_a, initial_b} = iterative_algorithm_initial(ctx)
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ctx = Map.put(ctx, :initial_a, initial_a)
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ctx = Map.put(ctx, :initial_b, initial_b)
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k = calc_k(alpha, delta, player_pre_rd_sq, variance_est, sys_const, 1)
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{initial_a, initial_b} = iterative_algorithm_initial(
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alpha, delta, player_pre_rd_sq, variance_est, sys_const, k
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)
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# Step 5.3
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ctx = Map.put(ctx, :initial_fa, calc_f(ctx, ctx.initial_a))
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ctx = Map.put(ctx, :initial_fb, calc_f(ctx, ctx.initial_b))
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initial_fa = calc_f(alpha, delta, player_pre_rd_sq, variance_est, sys_const, initial_a)
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initial_fb = calc_f(alpha, delta, player_pre_rd_sq, variance_est, sys_const, initial_b)
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# Step 5.4
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ctx = Map.put(ctx, :a, iterative_algorithm_body(
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ctx, ctx.initial_a, ctx.initial_b, ctx.initial_fa, ctx.initial_fb
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))
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a = iterative_algorithm_body(
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alpha, delta, player_pre_rd_sq, variance_est, sys_const, conv_tol,
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initial_a, initial_b, initial_fa, initial_fb
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)
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# Step 5.5
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ctx = Map.put(ctx, :new_player_volatility, calc_new_player_volatility(ctx))
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player_post_v = calc_new_player_volatility(a)
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# Step 6
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ctx = Map.put(ctx, :player_pre_rating_deviation, calc_player_pre_rating_deviation(
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ctx.player_rating_deviation_squared, ctx.new_player_volatility
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))
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player_post_base_rd = calc_player_post_base_rd(player_pre_rd_sq, player_post_v)
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# Step 7
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ctx = Map.put(ctx, :new_player_rating_deviation, calc_new_player_rating_deviation(ctx))
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ctx = Map.put(ctx, :new_player_rating, calc_new_player_rating(ctx))
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player_post_rd = calc_new_player_rating_deviation(player_post_base_rd, variance_est)
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player_post_r = calc_new_player_rating(results_effect, player_pre_r, player_post_rd)
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{ctx.new_player_rating, ctx.new_player_rating_deviation, ctx.new_player_volatility}
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{player_post_r, player_post_rd, player_post_v}
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end
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defp build_internal_result(ctx, result) do
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defp build_internal_result(player_pre_r, result) do
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result =
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Map.new
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|> Map.put(:score, Result.score(result))
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|> Map.put(:opponent_rating, Result.opponent_rating(result))
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|> Map.put(:opponent_rating_deviation, Result.opponent_rating_deviation(result))
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|> Map.put(:opponent_rating_deviation_g, calc_g(Result.opponent_rating_deviation(result)))
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|> Map.put(:opponent_r, Result.opponent_rating(result))
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|> Map.put(:opponent_rd, Result.opponent_rating_deviation(result))
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|> Map.put(:opponent_rd_g, calc_g(Result.opponent_rating_deviation(result)))
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Map.put(result, :e, calc_e(ctx.player_rating, result))
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Map.put(result, :e, calc_e(player_pre_r, result.opponent_r, result.opponent_rd_g))
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end
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# Calculation of the estimated variance of the player's rating based on game outcomes
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defp calc_variance_estimate(ctx) do
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ctx.results
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defp calc_variance_estimate(results) do
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results
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|> Enum.reduce(0.0, fn result, acc ->
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acc + :math.pow(result.opponent_rating_deviation_g, 2) * result.e * (1 - result.e)
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acc + :math.pow(result.opponent_rd_g, 2) * result.e * (1 - result.e)
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end)
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|> :math.pow(-1)
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end
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defp calc_delta(ctx) do
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ctx.results_effect * ctx.variance_estimate
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defp calc_delta(results_effect, variance_est) do
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results_effect * variance_est
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end
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defp calc_f(ctx, x) do
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defp calc_f(alpha, delta, player_pre_rd_sq, variance_est, sys_const, x) do
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:math.exp(x) *
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(:math.pow(ctx.delta, 2) - :math.exp(x) - ctx.player_rating_deviation_squared - ctx.variance_estimate) /
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(2 * :math.pow(ctx.player_rating_deviation_squared + ctx.variance_estimate + :math.exp(x), 2)) -
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(x - ctx.alpha) / :math.pow(ctx.system_constant, 2)
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(:math.pow(delta, 2) - :math.exp(x) - player_pre_rd_sq - variance_est) /
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(2 * :math.pow(player_pre_rd_sq + variance_est + :math.exp(x), 2)) -
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(x - alpha) / :math.pow(sys_const, 2)
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end
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defp calc_alpha(ctx) do
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:math.log(:math.pow(ctx.player_volatility, 2))
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defp calc_alpha(player_pre_v) do
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:math.log(:math.pow(player_pre_v, 2))
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end
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defp calc_new_player_volatility(%{a: a}) do
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defp calc_new_player_volatility(a) do
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:math.exp(a / 2)
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end
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defp calc_results_effect(ctx) do
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Enum.reduce(ctx.results, 0.0, fn result, acc ->
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acc + result.opponent_rating_deviation_g * (result.score - result.e)
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defp calc_results_effect(results) do
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Enum.reduce(results, 0.0, fn result, acc ->
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acc + result.opponent_rd_g * (result.score - result.e)
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end)
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end
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defp calc_new_player_rating(ctx) do
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ctx.player_rating + :math.pow(ctx.new_player_rating_deviation, 2) * ctx.results_effect
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defp calc_new_player_rating(results_effect, player_pre_r, player_post_rd) do
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player_pre_r + :math.pow(player_post_rd, 2) * results_effect
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end
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defp calc_new_player_rating_deviation(ctx) do
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1 / :math.sqrt(1 / :math.pow(ctx.player_pre_rating_deviation, 2) + 1 / ctx.variance_estimate)
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defp calc_new_player_rating_deviation(player_post_base_rd, variance_est) do
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1 / :math.sqrt(1 / :math.pow(player_post_base_rd, 2) + 1 / variance_est)
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end
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defp calc_player_pre_rating_deviation(player_rating_deviation_squared, player_volatility) do
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:math.sqrt((:math.pow(player_volatility, 2) + player_rating_deviation_squared))
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defp calc_player_post_base_rd(player_pre_rd_sq, player_pre_v) do
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:math.sqrt((:math.pow(player_pre_v, 2) + player_pre_rd_sq))
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end
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defp iterative_algorithm_initial(ctx) do
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initial_a = ctx.alpha
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defp iterative_algorithm_initial(alpha, delta, player_pre_rd_sq, variance_est, sys_const, k) do
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initial_a = alpha
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initial_b =
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if :math.pow(ctx.delta, 2) > ctx.player_rating_deviation_squared + ctx.variance_estimate do
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:math.log(:math.pow(ctx.delta, 2) - ctx.player_rating_deviation_squared - ctx.variance_estimate)
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if :math.pow(delta, 2) > player_pre_rd_sq + variance_est do
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:math.log(:math.pow(delta, 2) - player_pre_rd_sq - variance_est)
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else
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ctx.alpha - calc_k(ctx, 1) * ctx.system_constant
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alpha - k * sys_const
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end
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{initial_a, initial_b}
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end
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defp iterative_algorithm_body(ctx, a, b, fa, fb) do
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if abs(b - a) > ctx.convergence_tolerance do
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defp iterative_algorithm_body(alpha, delta, player_pre_rd_sq, variance_est, sys_const, conv_tol, a, b, fa, fb) do
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if abs(b - a) > conv_tol do
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c = a + (a - b) * fa / (fb - fa)
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fc = calc_f(ctx, c)
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fc = calc_f(alpha, delta, player_pre_rd_sq, variance_est, sys_const, c)
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{a, fa} =
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if fc * fb < 0 do
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{b, fb}
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else
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{a, fa / 2}
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end
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iterative_algorithm_body(ctx, a, c, fa, fc)
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iterative_algorithm_body(alpha, delta, player_pre_rd_sq, variance_est, sys_const, conv_tol, a, c, fa, fc)
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else
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a
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end
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end
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defp calc_k(ctx, k) do
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if calc_f(ctx, ctx.alpha - k * ctx.system_constant) < 0 do
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calc_k(ctx, k + 1)
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defp calc_k(alpha, delta, player_pre_rd_sq, variance_est, sys_const, k) do
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if calc_f(alpha, delta, player_pre_rd_sq, variance_est, sys_const, alpha - k * sys_const) < 0 do
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calc_k(alpha, delta, player_pre_rd_sq, variance_est, sys_const, k + 1)
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else
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k
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end
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end
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# g function
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defp calc_g(rating_deviation) do
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1 / :math.sqrt(1 + 3 * :math.pow(rating_deviation, 2) / :math.pow(:math.pi, 2))
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defp calc_g(rd) do
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1 / :math.sqrt(1 + 3 * :math.pow(rd, 2) / :math.pow(:math.pi, 2))
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end
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# E function
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defp calc_e(player_rating, result) do
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1 / (1 + :math.exp(-1 * result.opponent_rating_deviation_g * (player_rating - result.opponent_rating)))
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defp calc_e(player_pre_r, opponent_r, opponent_rd_g) do
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1 / (1 + :math.exp(-1 * opponent_rd_g * (player_pre_r - opponent_r)))
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end
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end
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