Figure A5.

Illustration of the new vector x^Δ, generated to improve the shape of the simplex. The vertex x₁ is replaced with either $x^{\Delta }=x_0+\gamma \rho v_{\mathcal{l}}$ or $x^{\Delta }=x_0-\gamma \rho v_{\mathcal{l}}$, whichever point results in a smaller value of $\widehat{\mathrm{\Phi }}$.