Tensor.sum_to: def of bendtorch@1.3.0.0
Import: import bendtorch@1.3.0.0/tensor.bend as Tensor
Lines 256-260 of bendtorch@1.3.0.0/tensor.bend: https://jend.leeeet.dev/read.txt?path=bendtorch@1.3.0.0/tensor.bend&start_line=256&end_line=260

import Base

# g + (dz summed down to a's shape): the gradient of an operand that was broadcast from a to o; dz comes back
def sum_to(+a: List<&2, Nat>, +o: List<&2, Nat>, dz: Tensor<o>, g: Tensor<a>) -> TP<o, a>:
  match dz g:
    case Tensor{d} Tensor{e}:
      tp_of(o, a, scatter_l(numel(o), 0, bmap(a, o), Array.get(F32, d, 0), Array.get(F32, e, imap(bmap(a, o), 0))))

Uses (11):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.get
  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=bendtorch@1.3.0.0/tensor.bend&name=TP
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=Tensor
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=bmap
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=imap
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=numel
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=scatter_l
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=tp_of