cross — Compute vector cross products in MATLAB and RunMat.

cross(A, B) computes vector cross products for matching 3-element vectors. For matrices and higher-rank arrays, it uses the first dimension of length 3 unless an explicit dimension is provided, following MATLAB semantics.

Syntax

C = cross(A, B)
C = cross(A, B, dim)

Inputs

Returns

Errors

How cross works

• Inputs A and B must be the same size.
• With no dimension argument, cross uses the first dimension whose extent is exactly 3.
• cross(A, B, dim) requires dim to be a valid array dimension and size(A, dim) == 3.
• The output has the same shape as the inputs because each input 3-vector produces one output 3-vector.
• Logical and integer inputs are promoted to double precision before evaluation.
• Real gpuArray inputs remain GPU-resident when the active provider implements the cross hook; otherwise RunMat gathers, evaluates on the host, and re-uploads the real result.

Does RunMat run cross on the GPU?

The WGPU provider computes real-valued cross products by gathering the three vector components into temporary device tensors, applying multiply/subtract kernels on-device, and scattering the results back into the output tensor. Providers that do not implement cross fall back to the host reference path.

GPU memory and residency

You usually do not need to call gpuArray explicitly for cross. RunMat keeps real-valued tensors on the GPU whenever the active provider supports the operation, and otherwise falls back to a gather -> host compute -> re-upload path automatically.

Examples

Computing the cross product of row vectors

a = [1 0 0];
b = [0 1 0];
c = cross(a, b)

Expected output:

c =
     0     0     1

Computing the cross product of column vectors

u = [1; 0; 0];
v = [0; 1; 0];
w = cross(u, v)

Expected output:

w =
     0
     0
     1

Applying cross row-wise across a matrix

A = [1 0 0; 0 1 0];
B = [0 1 0; 0 0 1];
C = cross(A, B, 2)

Expected output:

C =
     0     0     1
     1     0     0

Evaluating cross on GPU-resident tensors

G1 = gpuArray([1 0 0]);
G2 = gpuArray([0 1 0]);
G = cross(G1, G2);
result = gather(G)

Expected output:

result =
     0     0     1

Using cross with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how cross changes the result.

FAQ

Related Linalg functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how cross is executed, line by line, in Rust.

• View the source for cross in Rust on GitHub
• Learn how the RunMat runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

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