Definition. Post-training gain [ftip-005F]

For \(P\) and the no-training protocol \(P_0\) both satisfying the absolute-integrability condition of Convention [ftip-005D], the post-training gain is the real-valued difference

\[ \Delta J_{\rm ev}(P) =J_{\rm ev}(P)-J_{\rm ev}(P_0). \]

Both terms use the same evaluator, task law, utility, and inference budget. The subtraction does not compare different model families or evaluation procedures. In particular, \(+\infty -(+\infty )\) is not an admitted gain.