PyTorch Broadcasting Error Debugger
Debug PyTorch broadcasting errors. Enter two tensor shapes to see if they can broadcast, the result shape, and how to fix incompatible dimensions.
Built by Michael Lip
Frequently Asked Questions
What are PyTorch broadcasting rules?
Two tensors are broadcastable if, comparing dimensions from right to left: (1) dimensions are equal, (2) one of them is 1, or (3) one tensor has fewer dimensions. For example, [3,1] and [1,4] broadcast to [3,4]. But [3,2] and [4,2] do not broadcast because 3≠4 and neither is 1.
What does "The size of tensor a must match tensor b" mean?
This error means two tensors in an element-wise operation have incompatible shapes. Align shapes right-to-left and find where sizes differ and neither is 1. Fix: unsqueeze one tensor to add a dimension of size 1.
How do I fix broadcasting errors?
Common fixes: (1) unsqueeze to add a size-1 dimension. (2) expand to explicitly broadcast. (3) reshape to align dimensions. (4) Check if you accidentally squeezed a dimension earlier.
Does broadcasting copy data?
No. Broadcasting uses stride tricks to make a dimension of size 1 appear repeated. No data is copied, making it memory-efficient.
Is this tool free?
Yes. All HeyTensor tools are free, run in your browser, and require no signup.
About This Tool
Part of HeyTensor. All calculations run in your browser. Source code on GitHub.
Contact
Built by Michael Lip. Email [email protected].