I need to partition variable length vectors in neural network recently. For instance, the network input is {1,2,3,4,...,2n}, I want to partition two elements as a group, so the result seems like {{1,2},{3,4},...,{2n-1,2n}}, and notice that the input is variable length vectors.

I have tried to use ReshapeLayer[] to do this, the code like ReshapeLayer[{Automatic,2},"Input"->{"Varying"}], and received the message, ReshapeLayer::valfail: Validation failed for ReshapeLayer: with variable-length inputs, Automatic can only be used if the product of known input dimensions is a multiple of the product of known output dimensions.

So how can I do this via mathematica neural network? Is there anyway?


Thank you bro @Alexey Golyshev, but I still meet a problem, it seems that this method doesn't work inside a network.

What I want to do is, extract atom feature vectors according to my indexes, and partition two of them as a group.

Network inputs, Atom: Dimensions@Atom={n1,8}. NearIndex: Dimensions@NearIndex={n2,1}.

Full code:

enc=NetChain[{Ramp},"Input"->NetEncoder[{"Function", Partition[#,2] &, {"Varying",2,8}}]]



Then return the message NetGraph::tyfail2: Inferred inconsistent ranks for output of layer "Near" (a rank-3 array versus a matrix).

Network output dimensions should be:



  • $\begingroup$ Please show us the complete code of what you've tried. $\endgroup$
    – MarcoB
    Apr 26, 2021 at 12:50

1 Answer 1

enc = NetEncoder[{"Function", Partition[#, 2] &, {"Varying", 2}}]

enter image description here

net = NetChain[
  "Input" -> enc

enter image description here


{{1., 2.}, {3., 4.}, {5., 6.}, {7., 8.}, {9., 10.}}


net = NetGraph[
   1 -> ExtractLayer["Input" -> {"Varying", 2, 8}, "Output" -> {"Varying", 2, 8}]
   NetPort["Input"] -> NetPort[1, "Input"],
   NetPort["Position"] -> NetPort[1, "Position"]
  "Input" -> NetEncoder[{"Function", Partition[#, 2] &, {"Varying", 2, 8}}]

enter image description here

atom1 = Table[i, {i, 12}, {j, 8}];
atom2 = Table[i, {i, 24}, {j, 8}];
index1 = Partition[Range[4], 1];
index2 = Partition[Range[6], 1];
net[<|"Input" -> {atom1, atom2}, "Position" -> {index1, index2}|>]

enter image description here

Dimensions /@ %

{{4, 2, 8}, {6, 2, 8}}

  • $\begingroup$ Thanks bro, and I want to do extract first, then partition, so the output dimensions should be {{2,2,8},{3,2,8}}, is there any way? very thanks! $\endgroup$ Apr 27, 2021 at 8:22
  • $\begingroup$ Hello! I don't think that's possible. $\endgroup$ Apr 27, 2021 at 8:58

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