FP4 (E2M1)
Beginner
A tiny 4-bit number format with only 15 different values. It works for AI only with a shared multiplier for each small group.
Novice
A 4-bit float with 1 sign, 2 exponent and 1 mantissa bit. Its non-negative values are 0, 0.5, 1, 1.5, 2, 3, 4 and 6. It is always used with block scale factors, as in MXFP4 or NVFP4.
Expert
E2M1, bias 1, no Inf or NaN, max 6, one subnormal (0.5). Fifteen distinct values. Used as MXFP4 (32-element blocks, E8M0 scale, 4.25 bits/value) or NVFP4 (16-element blocks, E4M3 scale plus FP32 tensor scale, 4.5 bits/value).