pub type ArmCostFn<'a> = dyn Fn(&Graph, NodeId, usize, &[NodeId]) -> Option<u64> + 'a;Expand description
The composite-nanosecond cost of a branch arm, or None when it is
unknown or inadmissible — an unpriced/sentinel-cost op, or a variant
whose kernel is not available on the placed device. None means “this arm
cannot win”, so the conservative arm-0 oracle stands.
Arguments: (graph, branch, arm_index, arm_interior) where arm_interior
is the arm’s interior node set (the nodes on paths diverge → exit, arm 0’s
being the decomposed region and a fused arm’s being the single fused node).