Structured sparsity
Beginner
Zeros set out in a fixed pattern, like “two out of every four.” Then the chip knows where the gaps are.
Novice
A sparsity pattern with rules about where zeros may go. Examples: 2:4 (at most two nonzeros in every group of four), blocks of zeros, or whole rows or channels removed. Unstructured sparsity puts zeros anywhere.
Expert
Trades some accuracy at a given sparsity for regular memory access, cheap metadata and balanced work. N:M patterns (2:4 on recent GPUs) give a fixed 2× in hardware; block patterns let dense matrix engines skip whole tiles; channel pruning just makes a smaller dense layer.
Explained in Sparsity, in-memory and analog compute (Architectures).
See also: Sparsity, Sparse format (metadata).