Abstract JanusSampler is a single-objective, plug-and-play sampler that augments a CMA-ES host (evotorch backend) with JANUS-style, geometry-guided candidate generation (arXiv:2608.22862). It is the single-objective counterpart of JanusMooCmixSampler.
Population optimizers such as CMA-ES drive search through rank-based selection: the signal says one candidate is better than another, but not the local direction responsible for the improvement. JANUS recovers this missing geometric signal from a single estimated Jacobian J and uses it for both halves of the search, without replacing the host optimizer: