For the complete documentation index, see llms.txt. Markdown versions of all pages are available by appending .md to any URL (e.g. /max/get-started.md).
Mojo trait
Reducer
Parallel scalar reducer over the closed set of associative ops.
Reduces a scalar across all participants in the current parallel
scope; every participant receives the reduced value (like
MPI_Allreduce).
Concrete impls provide hardware-fast sum / max / min over a
closed set of dtypes, plus a generic fallback that combines any
ReduceOp via its join (slower; dtype-agnostic).
Implemented traits
Required methods
sum
def sum[dtype: DType](self, val: Scalar[dtype]) -> Scalar[dtype]
Returns the sum of val across all participants.
Parameters:
- dtype (
DType): The scalar dtype.
Args:
- val (
Scalar[dtype]): The per-participant value.
Returns:
Scalar[dtype]: The reduced sum, broadcast to every participant.
max
def max[dtype: DType](self, val: Scalar[dtype]) -> Scalar[dtype]
Returns the maximum of val across all participants.
Parameters:
- dtype (
DType): The scalar dtype.
Args:
- val (
Scalar[dtype]): The per-participant value.
Returns:
Scalar[dtype]: The reduced maximum, broadcast to every participant.
min
def min[dtype: DType](self, val: Scalar[dtype]) -> Scalar[dtype]
Returns the minimum of val across all participants.
Parameters:
- dtype (
DType): The scalar dtype.
Args:
- val (
Scalar[dtype]): The per-participant value.
Returns:
Scalar[dtype]: The reduced minimum, broadcast to every participant.
generic
def generic[S: ReduceOp](self, mut state: S)
Combines state across all participants using only join — the multi-field path for monoids whose state isn't decomposable into scalar sum/max/min (Welford, ArgMax, ArgMin, …).
Impls pick by state size: small states (a few uint32 words) use
a register-only warp-shuffle butterfly, larger states a shmem
tree — both valid since ReduceOp is TrivialRegisterPassable.
Monoids that can decompose (ReduceSum, ReduceMax,
OnlineLogSumExp, …) instead call reducer.sum/max/min
directly, which compile to one hardware redux.sync per field
and are faster.
Parameters:
- S (
ReduceOp): The monoid type being combined.
Args:
- state (
S): Per-participant state; on return, holds the combined value on every participant.
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