add both integer and float implementations

Author: tiagodavi

nx/lib/nx.ex

@@ -3268,7 +3268,7 @@ defmodule Nx do
   @doc ~S"""
   Split a tensor into train and test subsets.
 
-  `split` split must be an integer greater than zero and less than the length of the tensor.
+  `split` split must be either an integer greater than zero and less than the length of the tensor or a float number between `0.0` and `1.0`.
 
   ## Options
 
@@ -3315,67 +3315,33 @@ defmodule Nx do
       ]
     >
 
-    iex> {train, test} = Nx.split(Nx.tensor([[3, 6, 5, 20], [26, 75, 3, 9], [23, 4, 1, 5]], names: [:rows, :columns]), 2, axis: :columns)
+    iex> {train, test} = Nx.split(Nx.tensor([[3, 6, 5, 9], [26, 75, 3, 20], [23, 4, 1, 56], [40, 6, 78, 94]]), 0.5, axis: 0)
     iex> train
     #Nx.Tensor<
-      s64[rows: 3][columns: 2]
+      s64[2][4]
       [
-        [3, 6],
-        [26, 75],
-        [23, 4]
-      ]
-    >
-    iex> test
-    #Nx.Tensor<
-      s64[rows: 3][columns: 2]
-      [
-        [5, 20],
-        [3, 9],
-        [1, 5]
-      ]
-    >
-
-    iex>{train, test} = Nx.split(Nx.tensor([[3, 6, 5, 20], [26, 75, 3, 9], [23, 4, 1, 5]], names: [:rows, :columns]), 2, axis: :rows)
-    iex> train
-    #Nx.Tensor<
-      s64[rows: 2][columns: 4]
-      [
-        [3, 6, 5, 20],
-        [26, 75, 3, 9]
+        [3, 6, 5, 9],
+        [26, 75, 3, 20]
       ]
     >
     iex> test
     #Nx.Tensor<
-      s64[rows: 1][columns: 4]
+      s64[2][4]
       [
-        [23, 4, 1, 5]
+        [23, 4, 1, 56],
+        [40, 6, 78, 94]
       ]
     >
   """
   @doc type: :indexed
   def split(tensor, split, opts \\ [])
 
-  def split(%T{shape: shape} = tensor, split, opts) do
+  def split(%T{shape: shape} = tensor, split, opts) when is_integer(split) do
     opts = keyword!(opts, axis: 0)
     axis = Keyword.fetch!(opts, :axis)
 
-    if is_integer(split) and split > 0 do
-      axis_values = axes(tensor)
-      axis_names = names(tensor)
-
-      axis =
-        cond do
-          is_integer(axis) and axis in axis_values ->
-            axis
-
-          is_atom(axis) and axis in axis_names ->
-            dimensions = Enum.zip(axis_names, axis_values)
-            dimensions[axis]
-
-          true ->
-            raise ":axis is out of tensor bounds."
-        end
-
+    if split > 0 do
+      axis = find_axis(tensor, axis)
       values = elem(shape, axis)
       size = values - split
 
@@ -3388,6 +3354,35 @@ defmodule Nx do
     end
   end
 
+  def split(%T{shape: shape} = tensor, split, opts) when is_float(split) do
+    opts = keyword!(opts, axis: 0)
+    axis = Keyword.fetch!(opts, :axis)
+
+    if split > 0.0 and split < 1.0 do
+      axis = find_axis(tensor, axis)
+
+      values = elem(shape, axis)
+
+      split_size = Kernel.ceil(split * values)
+
+      split_size =
+        cond do
+          split_size < 1 -> 1
+          split_size >= values -> 1
+          true -> split_size
+        end
+
+      remaining_size = values - split_size
+
+      {
+        slice_along_axis(tensor, 0, split_size, axis: axis),
+        slice_along_axis(tensor, split_size, remaining_size, axis: axis)
+      }
+    else
+      raise "split must be a float number between 0.0 and 1.0."
+    end
+  end
+
   @doc """
   Broadcasts `tensor` to the given `broadcast_shape`.
 
@@ -16184,4 +16179,21 @@ defmodule Nx do
       end)
     end
   end
+
+  defp find_axis(tensor, axis) do
+    axis_values = axes(tensor)
+    axis_names = names(tensor)
+
+    cond do
+      is_integer(axis) and axis in axis_values ->
+        axis
+
+      is_atom(axis) and axis in axis_names ->
+        dimensions = Enum.zip(axis_names, axis_values)
+        dimensions[axis]
+
+      true ->
+        raise ":axis is out of tensor bounds."
+    end
+  end
 end

nx/test/nx_test.exs

@@ -3034,6 +3034,16 @@ defmodule NxTest do
                    end
     end
 
+    test "split is a float out of bounds" do
+      tensor = Nx.iota({10, 2}, names: [:x, :y])
+
+      assert_raise RuntimeError,
+                   "split must be a float number between 0.0 and 1.0.",
+                   fn ->
+                     Nx.split(tensor, 1.0)
+                   end
+    end
+
     test "split is greater than tensor length" do
       tensor = Nx.iota({10, 2}, names: [:x, :y])
 
@@ -3064,6 +3074,14 @@ defmodule NxTest do
                    end
     end
 
+    test "split into 50% for training and 50% for testing with floats on columns" do
+      tensor = Nx.iota({4, 4}, names: [:rows, :columns])
+      {train, test} = Nx.split(tensor, 0.5, axis: :columns)
+
+      assert {4, 2} == Nx.shape(train)
+      assert {4, 2} == Nx.shape(test)
+    end
+
     test "split into 70% for training and 30% for testing along a named :axis" do
       tensor = Nx.iota({100, 6}, names: [:rows, :columns])
       {train, test} = Nx.split(tensor, 70, axis: :rows)