F64LdlDecomposition
class F64LdlDecomposition(val n: Int, val ldl: DoubleArray, val ipiv: IntArray, val failedAt: Int = NOT_SINGULAR)(source)
A symmetric indefinite factorization A = L·D·Lᵀ in LAPACK dsytrf lower packed form. ldl and ipiv are live buffers, not copies, so treat them as read-only.