Memory-bound
Beginner
A job is waiting on memory when the math parts of the chip sit idle, because the numbers they need can’t arrive fast enough.
Novice
A workload whose run time is set by how many bytes it moves, because it does too little work per byte. More bandwidth or more reuse of each byte would speed it up; more math hardware would not.
Expert
Arithmetic intensity below the ridge point, so attainable = bandwidth × intensity. Fixes raise the intensity (batching, fusion, tiling, fewer bits per value) or the bandwidth.
Explained in What the workload needs (Architectures).
See also: Compute-bound, Ridge point (machine balance).