isfinite — Test finite values element-wise in MATLAB and RunMat.

mask = isfinite(x) returns a logical mask indicating which elements are finite (not NaN or ±Inf). Output shape and type handling follow MATLAB semantics.

Syntax

tf = isfinite(A)

Inputs

Returns

Errors

How isfinite works

• Numeric scalars return a logical scalar (true/false).
• Numeric arrays return a logical array of the same size, with true wherever the corresponding element is finite.
• Complex inputs report true when both the real and imaginary components are finite.
• Logical inputs return true because logical values (0 or 1) are finite by construction.
• Character arrays return logical arrays of ones (characters map to finite Unicode code points).
• String scalars return false; string arrays return logical arrays of zeros, mirroring MATLAB behavior.
• When the input is a gpuArray, RunMat keeps the computation on the device if the active acceleration provider implements the logical_isfinite hook; otherwise the runtime gathers the data back to the host automatically.

Does RunMat run isfinite on the GPU?

When RunMat Accelerate is active, isfinite looks for the provider hook logical_isfinite. Providers that implement the hook execute the finite test entirely on the GPU, producing a logical gpuArray result without any host transfers. If the hook is absent, RunMat gathers the input tensor back to the CPU, computes the mask on the host, and returns a regular logical array so the builtin always succeeds.

GPU memory and residency

You usually do not need to call gpuArray explicitly. RunMat's auto-offload planner keeps tensors on the GPU across fused expressions when that improves performance. You can still seed residency manually with gpuArray for compatibility with MATLAB scripts or when you want fine-grained control over data movement.

Examples

Check if a scalar is finite

result = isfinite(42)

Expected output:

result =
     1

Create a finite mask for a numeric matrix

A = [1 NaN; Inf 4];
mask = isfinite(A)

Expected output:

mask =
  2×2 logical array
     1     0
     0     1

Identify finite components in a complex array

Z = [1+2i Inf+0i 3+NaNi];
mask = isfinite(Z)

Expected output:

mask =
  1×3 logical array
     1     0     0

Apply isfinite to character data

chars = ['R' 'u' 'n'];
mask = isfinite(chars)

Expected output:

mask =
  1×3 logical array
     1     1     1

Run isfinite directly on the GPU

G = gpuArray([1 -Inf 5]);
mask_gpu = isfinite(G);
mask = gather(mask_gpu)

Expected output:

mask =
  1×3 logical array
     1     0     1

Using isfinite with coding agents

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

FAQ

Related Logical functions

Open-source implementation

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

• View the source for isfinite 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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