Function memory_bound 

pub fn memory_bound(
    client: &Client,
    access: MemoryAccess,
    work: Work,
    threshold: f32,
) -> AutotuneBound

The memory half of a roofline: work’s bytes against the ceiling in the direction access names, at the work’s own footprint.

The direction is the caller’s because a read-dominated kernel exceeds a copy’s bandwidth, half of which is a direction it never uses. Bounding one by MemoryAccess::Copy passes a candidate at a fraction of the bus for close to peak.