sketch_count_sketch_negative_bench.nx

sketch_count_sketch_negative_bench.nx -- negative-insert capability bench. CLAIM TO VALIDATE: CountSketch (Charikar et al. 2002) natively supports NEGATIVE inserts -- it tracks the SIGNED sum of inserts per key (a TURNSTILE stream). Apache DataSketches queues but does NOT ship CountSketch; their only frequency primitive (CMS) handles INSERT-ONLY streams (cash-register). Every other in-tree frequency primitive (SpaceSaving, MisraGries, LossyCounting) is also INSERT-ONLY. This bench demonstrates: CountSketch correctly tracks net counts under mixed +/- inserts; CMS (forced to accept negative inserts) silently corrupts. CAPABILITY EXCEED across the entire freq family. WORKLOAD: Per-key insert pattern (item 1): +1000, +500, -200, -100, +50, -50 Net per item 1: 1200 Item 2: +800, -100, +200 -> net 900 Item 3: +300, -50 -> net 250 Plus 200 singleton-positive noise items. MEASUREMENT: - CountSketch must return est within reasonable noise band of NET count - CMS estimate is UNRELIABLE under negative inserts (rows can go negative; the min-over-rows guarantee breaks). We document this by asserting CountSketch is materially closer to truth.