PEP Dashboard

PEP dashboard

Demonstration of the main capabilities of the Performance Estimation Methodology. Exact worst-case analysis of a fixed-step first-order method on \(L\)-smooth convex functions. Edit the method; the performance estimation problem is solved again in your browser.

Fixed-coefficient first-order method

\(\displaystyle x_i \;=\; x_0 - \frac{1}{L}\sum_{j} H_{ij}\,\nabla f(x_j), \qquad i = 1,\dots,N\)

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Presets

Measure

Exact worst-case bound on L-smooth convex functions

Worst-case function

Proof from the dual

Multiplier \(\lambda_{ij}\) (row \(i\), column \(j\)) weights the interpolation inequality \(Q_{ij} = f_i - f_j - \langle g_j,\, x_i - x_j\rangle - \tfrac{1}{2L}\|g_i - g_j\|^2 \ge 0\), with \(f_i = f(x_i)\), \(g_i = \nabla f(x_i)\) and \(*\) the minimizer.

Multipliers \(\lambda_{ij}\)
Dual slack matrix \(S \succeq 0\); its quadratic form in \(x_0 - x_*\) and the gradients is the sum of squares