Reduce.fiber_fast: def of bendtorch-core@0.1.0.0
Import: import bendtorch-core@0.1.0.0/src/autograd/reduce.bend as Reduce
Lines 138-159 of bendtorch-core@0.1.0.0/src/autograd/reduce.bend: https://jend.leeeet.dev/read.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&start_line=138&end_line=159

import Base
import bendtorch-core@0.1.0.0/src/shape/core.bend as Shape

# `fiber`, the same words added in the same order, except that a row whose
# rows below all take one digit (`single`, which is `single_below` of the
# rows; a later digit of the same row passes False) walks its digits in one
# strided loop: below digit d it reads the one word at base + right * d +
# single_offset(rest, others, target % left, 0), with no closure per word.
# Column sums, row sums and batch sums over one axis take that loop.
def fiber_fast(+rows: List<&2, Shape.Row>, +extents: List<&2, Nat>, fuel: Nat, single: Bool, +target: Nat, +base: Nat, +digit: Nat,
  accumulator: F32, array: Array<F32>) -> F32 & Array<F32>:
  match rows extents fuel single:
    case Nil{} _ _ single:
      leaf_add(accumulator, Array.get(F32, array, U32.from_nat(base)))
    case Shape.Row{+stride, +left, +right} <> +rest +extent <> +others fuel True{}:
      strided(fuel, right, base, digit, single_offset(rest, others, Nat.mod(target, left), 0n), accumulator, array)
    case Shape.Row{+stride, +left, +right} <> +rest +extent <> +others 0n False{}:
      (accumulator, array)
    case Shape.Row{+stride, +left, +right} <> +rest +extent <> +others 1n+remaining False{}:
      +inner = Nat.mod(target, left)
      walk_next(value => kept => fiber_fast(rows, extents, remaining, False{}, target, base, 1n+digit, value, kept),
        fiber_fast(rest, others, first_span(rest, others), single_below(rest, others), inner, step_offset(base, right, digit),
          first_digit(rest, inner), accumulator, array))
    case Shape.Row{+stride, +left, +right} <> +rest Nil{} _ single:
      (accumulator, array)

Uses (19):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.get
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.mod
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.from_nat
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=first_digit
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=first_span
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=leaf_add
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=single_below
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=single_offset
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=step_offset
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=strided
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=walk_next
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/shape/core.bend&name=Row