forked from 1b-agent/fieldcraft-upstream
jyvikoandClaude Opus 5.5
c09ccc8a59
A tangent that is not positive definite is factored by LDLᵀ (Cholesky first, one symbolic factorization) instead of cutting the increment back; each iteration records the tangent's negative eigenvalues and the summary warns when a converged state keeps some. A model that can move freely is still an error at its first tangent, located by the undeformed Cholesky factor; a singular tangent later is a cutback. Nearly incompressible hybrid hex8, hex20 and tet10 at ν = 0.4999 under prescribed displacement now converge to the closed form. Co-Authored-By: Claude Opus 5.5 <[email protected]>