# PyTorch torch.sum() Method

PyTorch torch.sum() method “returns the sum of all elements in the input tensor.”

## Syntax

``````torch.sum(input, dim, keepdim=False, *, dtype=None)
``````

## Parameters

1. input (Tensor): It is an input tensor.
2. dim (int or tuple of ints, optional): It is the dimension or dimensions to reduce. If None, all dimensions are reduced.
3. keepdim (bool):  Whether the output tensor has dim retained or not.
4. dtype: The desired data type of the returned tensor. If specified, the input tensor is cast to dtype before operating.

## Example 1: Sum all elements of a tensor

``````import torch

a = torch.Tensor([1, 2, 3, 4, 5])

result = torch.sum(a)

print(result)
``````

Output

``````tensor(15.)
``````

## Example 2: Sum along a specific dimension

``````import torch

a = torch.Tensor([[1, 2], [3, 4], [5, 6]])

result = torch.sum(a, dim=0)

print(result)
``````

Output

``````tensor([ 9., 12.])
``````

## Example 3: Sum along multiple dimensions

``````import torch

a = torch.Tensor([[[1, 2], [3, 4]], [[5, 6], [7, 8]]])

result = torch.sum(a, dim=(0, 1))

print(result)
``````

Output

``````tensor([16., 20.])
``````

## Example 4: Keep dimensions

``````import torch

a = torch.Tensor([[1, 2], [3, 4], [5, 6]])

result = torch.sum(a, dim=0, keepdim=True)

print(result)``````

Output

``tensor([[ 9., 12.]])``

## Example 6: Torch sum a tensor along an axis

To sum a tensor along an axis in PyTorch, use the “torch.sum() function”. The torch.sum() function accepts two arguments: the tensor you want to sum and the axis you want to sum over. The axis can be a single integer or a list of integers. If you specify a list of integers, the tensor will be summed over all the axes specified in the list.

``````import torch

tensor = torch.rand(3, 4)

sum = torch.sum(tensor, dim=0)

print(sum)
``````

Output

``tensor([1.1096, 1.9846, 0.5725, 1.8936])``

The torch.sum() function is used to sum along the last axis of a tensor. To do this, you can use the -1 argument for the dim parameter.

``````import torch

tensor = torch.rand(3, 4)

sum = torch.sum(tensor, dim=-1)

print(sum)
``````

Output

``tensor([3.1583, 2.5213, 2.4922])``

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