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How to perform element-wise subtraction on tensors in PyTorch?
To perform element-wise subtraction on tensors, we can use the torch.sub() method of PyTorch. The corresponding elements of the tensors are subtracted. We can subtract a scalar or tensor from another tensor. We can subtract a tensor from a tensor with same or different dimension. The dimension of the final tensor will be same as the dimension of the higher-dimensional tensor.
Steps
Import the required library. In all the following Python examples, the required Python library is torch. Make sure you have already installed it.
Define two or more PyTorch tensors and print them. If you want to subtract a scalar quantity, define it.
Subtract a scalar or a tensor from another tensor using torch.sub() and assign the value to a new variable. You can also subtract a scalar quantity from the tensor. Subtracting the tensors using this method does not make any change in the original tensors.
Print the final tensor.
Example 1
Here, we will have a Python 3 program to subtract a scalar quantity from a tensor. We will see three different ways to perform the same task.
# Python program to perform element-wise subtraction
# import the required library
import torch
# Create a tensor
t = torch.Tensor([1.5, 2.03, 3.8, 2.9])
print("Original Tensor t:\n", t)
# Subtract a scalar value to a tensor
v = torch.sub(t, 5.60)
print("Element-wise subtraction result:\n", v)
# Same result can also be obtained as below
t1 = torch.Tensor([5.60])
w = torch.sub(t, t1)
print("Element-wise subtraction result:\n", w)
# Other way to do above operation
t2 = torch.Tensor([5.60,5.60,5.60,5.60])
x = torch.sub(t, t2)
print("Element-wise subtraction result:\n", x)Output
Original Tensor t: tensor([1.5000, 2.0300, 3.8000, 2.9000]) Element-wise subtraction result: tensor([-4.1000, -3.5700, -1.8000, -2.7000]) Element-wise subtraction result: tensor([-4.1000, -3.5700, -1.8000, -2.7000]) Element-wise subtraction result: tensor([-4.1000, -3.5700, -1.8000, -2.7000])
Example 2
The following program shows how to subtract a 1-D tensor from a 2-D tensor.
# Import necessary library
import torch
# Create a 2D tensor
T1 = torch.Tensor([[8,7],[4,5]])
# Create a 1-D tensor
T2 = torch.Tensor([10, 5])
print("T1:\n", T1)
print("T2:\n", T2)
# Subtract 1-D tensor from 2-D tensor
v = torch.sub(T1, T2)
print("Element-wise subtraction result:\n", v)Output
T1: tensor([[8., 7.], [4., 5.]]) T2: tensor([10., 5.]) Element-wise subtraction result: tensor([[-2., 2.], [-6., 0.]])
Example 3
The following program shows how to subtract a 2D tensor from a 1D tensor.
# Python program to subtract 2D tensor from 1D tensor
# Import the library
import torch
# Create a 2D tensor
T1 = torch.Tensor([[1,2],[4,5]])
# Create a 1-D tensor
T2 = torch.Tensor([10, 5])
print("T1:\n", T1)
print("T2:\n", T2)
# Subtract 2-D tensor from 1-D tensor
v = torch.sub(T2, T1)
print("Element-wise subtraction result:\n", v)Output
T1: tensor([[1., 2.], [4., 5.]]) T2: tensor([10., 5.]) Element-wise subtraction result: tensor([[9., 3.], [6., 0.]])
You can notice that the final tensor is a 2D tensor.
Example 4
The following program shows how to subtract a 2D tensor from a 2D tensor.
# import the library
import torch
# Create two 2-D tensors
T1 = torch.Tensor([[8,7],[3,4]])
T2 = torch.Tensor([[0,3],[4,9]])
print("T1:\n", T1)
print("T2:\n", T2)
# Subtract above two 2-D tensors
v = torch.sub(T1,T2)
print("Element-wise subtraction result:\n", v)Output
T1: tensor([[8., 7.], [3., 4.]]) T2: tensor([[0., 3.], [4., 9.]]) Element-wise subtraction result: tensor([[ 8., 4.], [-1., -5.]])
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