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Equation 18 · The Type Chart Is a Payoff Matrix, and the Metagame Only Half-Solves It

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DKL(p ∥ q)=∑ipilog⁡2(pi/qi)D_{\mathrm{KL}}(p \,\|\, q) = \sum_i p_i \log_2(p_i/q_i)

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Inputs and operationssum_i p_i log_2(p_i/q_i)
Result or conditionD_KL(p | q)
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DKLD_{\mathrm{KL}}

Symbol D_KL

DKD_KL is part of the quantity the equation computes from the expression on the right.

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pp

Symbol p

p is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

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qq

Symbol q

q is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

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ii

Symbol i

i appears in the bound of this sum. The bound states where the repeated operation starts, ends, or which values it includes.

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pip_i

Symbol p_i

pip_i is an input to the expression that computes the quantity on the left.

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qiq_i

Symbol q_i

qiq_i is an input to the expression that computes the quantity on the left.

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=

=

The expressions on both sides represent the same quantity under the stated assumptions.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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ii

Starting index or lower bound: i

This label says where the repeated addition, multiplication, or accumulation starts. Read its value or condition together with the article’s description of the index.

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What the article says around this equation

Scoring the fit with Kullback–Leibler divergence, DKL(p ∥ q)D_{\mathrm{KL}}(p \,\|\, q) = ∑i\sum_i pip_i log⁡2(pi/qi)\log_2(p_i/q_i) , from the observed August distribution to each candidate: the solved game scores 10.15 bits, the uniform null scores 0.045 bits, and July’s raw persistence scores 0.00068 bits. On a chi-square test against the eight species’ actual August battle counts (summing to 2,137,239 team-appearances, treating each candidate distribution as the expected shares), the solved game scores approximately 2.3×\times10^{13} — a figure that large only because the model assigns four real, frequently-played species an expected share of essentially zero, and squaring a large real count against a near-zero…
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Scoring the fit with Kullback–Leibler divergence, DKL(p ∥ q)D_{\mathrm{KL}}(p \,\|\, q) = ∑i\sum_i pip_i log⁡2(pi/qi)\log_2(p_i/q_i) , from the observed August distribution to each candidate: the solved game scores 10.15 bits, the uniform null scores 0.045 bits, and July’s raw persistence scores 0.00068 bits. On a chi-square test against the eight species’ actual August battle counts (summing to 2,137,239 team-appearances, treating each candidate distribution as the expected shares), the solved game scores approximately 2.3×\times10^{13} — a figure that large only because the model assigns four real, frequently-played species an expected share of essentially zero, and squaring a large real count against a near-zero expectation explodes the statistic — against 159,897 for uniform and 4,371 for persistence. Every test agrees, and by a wide margin: the equilibrium this piece computed from the actual, official type chart is a dramatically worse predictor of the actual ladder than either “assume no type advantage matters” or “assume nothing changed since last month.”

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