What are advanced techniques for clock tree optimization?

Advanced CTS techniques: Multi-source CTS (multiple clock entry points for lower skew/latency), Concurrent clock and data optimization (CCD, optimize together for useful skew), OCV-aware CTS (build trees considering variation), Mesh + tree hybrid (mesh for tight skew regions), Multi-corner CTS (optimize across corners simultaneously), Power-aware CTS (minimize buffer count and clock capacitance), and Blockage-aware routing. Implementation: Define clock routing non-default rules (NDRs), specify skew groups for timing-critical blocks, use clock tree exceptions for special handling. Balance trade-offs between power, skew, latency, and variation tolerance.