HowToSD-ComfyUI-Data-Analysis/docs/reference/pt_gather.md

Pt Gather

Generates a tensor based on the index tensor using PyTorch's gather function.

Specify the dim field using an integer to indicate the axis along which to gather elements. Each input tensor element is selected based on the index tensor.

For example, consider the following input tensor:

[ [10, 20, 30, 40, 50],
  [100, 200, 300, 400, 500]]

and the corresponding index tensor:

[ [0, 4, 3, 2, 0],
  [4, 3, 0, 0, 0]]

If dim = 0, the function scans row-wise, treating each index value as a row index. If dim = 1, it scans column-wise, interpreting each index value as a column index.

Let's analyze the case where dim = 1:

• Start at row 0, column 0.

• The index at this position is index[0, 0] = 0.

• PyTorch selects the value at position 0 from the array [10, 20, 30, 40, 50], which is 10.

• The result at this stage is:

  [[10, ?, ?, ?, ?]
   [?, ?, ?, ?, ?]]
  

• Moving to column 1: index[0, 1] = 4.

• The value at index 4 in [10, 20, 30, 40, 50] is 50.

• The updated result is:

  [[10, 50, ?, ?, ?]
   [?, ?, ?, ?, ?]]
  

• Repeating this process for all elements constructs the final gathered tensor.

Input

Name	Data type
tens	Tensor
dim	Int
index	String

Output

Data type
Tensor

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Category: PyTorch wrapper - Indexing and Slicing Operations

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