Runtimeerror: expected scalar type float but found double

One of the common errors is runtimeerror: expected scalar type float but found double. This error occurs if a program expects a float but instead receives a double.

In this article, we will explain this error in detail and provide you with the necessary solutions to resolve it.

What is a Scalar Type and a Double?

Before we proceed into the error, let’s first define the scalar type and double.

• A scalar type is a single value, while a double is a type of data that can store numbers with decimal points.

• A scalar type can be an integer or a float, which is a number with a decimal point.

What is the difference between Scalar Type and Double?

• Scalar type and double are different in terms on how they store and produce data.

• A scalar type can only store a single value, while a double can store multiple values in a single variable.

• Double is more accurate and can store numbers with decimal points, while scalar types are commonly limited to whole numbers.

Common Possible Causes of the Error

The error expected scalar type float but found double typically occurs due to various reasons. The following are some of the most common causes of this error:

• Incorrect Input Data Type
• Incompatible Variable Types
• Mismatched Tensors

Reproduce the Error

import torch

tensor1 = torch.randn(3, 4, dtype=torch.float)
tensor2 = torch.randn(4, 3, dtype=torch.double)

result = torch.matmul(tensor1, tensor2)
print(result)

Output:

Traceback (most recent call last):
File “C:\Users\Joken\PycharmProjects\pythonProject6\main.py”, line 6, in
result = torch.matmul(tensor1, tensor2)
RuntimeError: expected scalar type Float but found Double

How to Fix the Error?

Now that you understand some of the common causes of the error, here are some solutions to fix it:

Solution 1: Change the Data Type of the Input to Fix the Error

When the error is caused by an incorrect input data type, you can fix it by modifying the data type of the input.

For example, when the function expects a float input and you pass a double, you can cast the input to float before passing it to the function.

def calculate_average(num1: float, num2: float) -> float:
    return (num1 + num2) / 2
a = 5
b = 10
average = calculate_average(float(a), float(b))
print(average)

Output:

7.5

Solution 2: Cast Variables to the Same Data Type to Fix the Error

If the error is caused by incompatible variable types, you can fix it by casting the variables to the same data type.

For example, if you have a double variable and a scalar variable, you can cast the scalar variable to a double before performing an operation that requires both variables.

x = 3.14
y = 2


# Cast y to a double to fix the error
result = x + float(y)

# Now the operation should work without error
print(result)  # Output: 5.14

Output:

5.140000000000001

Solution 3: Ensure Tensors are the Same Type

If the error is caused by mismatched tensors, you can fix it by ensuring that both tensors have the same data type.

You can cast one of the tensors to match the other before performing an operation that requires both tensors.

Additional Resources

• Cannot add middleware after an application has started
• Java gateway process exited before sending its port number
• runtimeerror: cudnn error: cudnn_status_not_initialized

Conclusion

In conclusion, the “runtimeerror: expected scalar type float but found double” error can be caused by different factors.

However, by knowing the difference between scalar type and double, and the common causes of this error, you can quickly fix it.

To fix the error, you need to make sure that your input data, variables, and tensors have the correct data type. You can also cast variables or tensors to the same data type to resolve the error.

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