Tensor.sum_axis_bwd: def of bendtorch@1.3.0.0
Import: import bendtorch@1.3.0.0/tensor.bend as Tensor
Lines 283-287 of bendtorch@1.3.0.0/tensor.bend: https://jend.leeeet.dev/read.txt?path=bendtorch@1.3.0.0/tensor.bend&start_line=283&end_line=287

import Base

# the gradient of sum_axis: dy (shape remove(s, k)) copied along axis k; dy comes back
def sum_axis_bwd(+s: List<&2, Nat>, +k: Nat, dy: Tensor<remove(s, k)>) -> TP<remove(s, k), s>:
  match dy:
    case Tensor{d}:
      tp_of(remove(s, k), s, gather_l(numel(s), 0, drop_map(s, k), Array.get(F32, d, imap(drop_map(s, k), 0)), new(numel(s))))

Uses (13):
  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=drop_map
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=gather_l
  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=new
  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=remove
  https://jend.leeeet.dev/definition.txt?path=bendtorch@1.3.0.0/tensor.bend&name=tp_of