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

**Syntax**

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

**Parameters**

**input (Tensor)**: It is an input tensor.

**dim (int or tuple of ints, optional)**: It is the dimension or dimensions to reduce. If None, all dimensions are reduced.

**keepdim (bool)**: Whether the output tensor has dim retained or not.**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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Krunal Lathiya is a seasoned Computer Science expert with over eight years in the tech industry. He boasts deep knowledge in Data Science and Machine Learning. Versed in Python, JavaScript, PHP, R, and Golang. Skilled in frameworks like Angular and React and platforms such as Node.js. His expertise spans both front-end and back-end development. His proficiency in the Machine Learning frameworks like PyTorch and Tensorflow is a testament to his versatility and commitment to the craft.