float8_e4m3 data type

Defines an 8-bit floating point representation with:

• 1 sign bit
• 4 exponent bits, with bias of 7
• 3 mantissa bits
• IEEE 754-compliant, with NaN and +/-inf.
• Subnormal numbers when biased exponent is 0.

Data type name

The data type is specified as "float8_e4m3".

Configuration

None.

Fill value representation

The fill value is specified in the same way as the core IEEE 754 floating point numbers: https://zarr-specs.readthedocs.io/en/latest/v3/core/v3.0.html#fill-value

The constant "NaN" corresponds to a representation of "0x7c".

Codec compatibility

bytes

Encoded as a 1-byte value 0bSEEEEMMM. The "endian" parameter has no effect.

See also

• Bit layout described by https://arxiv.org/abs/2209.05433
• Specified as the E4M3 format by OpenCompute MX.
• Python implementation available at https://pypi.org/project/ml-dtypes/
• Implemented in LLVM/MLIR as Float8E4M3.

Current maintainers

• Jeremy Maitin-Shepard (@jbms), Google