> ## Documentation Index
> Fetch the complete documentation index at: https://luminair.gizatech.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Shape Tracking

> Compile-time shape tracking

When working with a [GraphTensor](/concepts/graph-tensor) in LuminAIR, you may notice that its type includes a specific generic parameter.
This parameter encodes the tensor’s shape directly at the type level, enabling compile-time shape tracking.

# What Does the Shape Parameter Represent?

Consider the following example:

```rust theme={null}
let a: GraphTensor<R1<3>> = cx.tensor();
```

Here, `R1<3>` is the shape parameter of the `GraphTensor`.
Let’s break it down:

* `R1`: Represents the rank of the tensor, which is the number of dimensions it has.
  In this case, `R1` denotes a rank-1 tensor (a one-dimensional tensor).
* `<3>`: Specifies the size of the tensor along its single dimension.
  Here, `<3>` means the tensor contains 3 elements

Together, `R1<3>` defines a one-dimensional tensor with 3 elements—a 3-dimensional vector.

# How Does Shape Tracking Work?

The shape parameter (`R1<N>`) is implemented as a type alias for `(Const<N>,)`,
where `Const<N>` is a compile-time constant representing the size of the tensor.

This design allows Rust to enforce tensor shapes at compile time, ensuring that:

1. **Shape Mismatches Are Caught Early**: Tensor operations are only allowed between tensors with compatible shapes.
2. **No Runtime Shape Calculations**: Since shapes are encoded in types, there’s no need to compute or validate shapes during execution.