ceil — Round values toward positive infinity in MATLAB and RunMat.

ceil(X) rounds each element of X toward positive infinity, returning the smallest integer greater than or equal to each value. Optional arguments support digit/significant-digit and 'like' forms consistent with MATLAB and RunMat.

Syntax

Y = ceil(X)
Y = ceil(X, N)
Y = ceil(X, N, mode)
Y = ceil(X, "like", prototype)

Inputs

Returns

Errors

How ceil works

• Works on scalars, vectors, matrices, and higher-dimensional tensors with MATLAB broadcasting semantics.
• ceil(X, N) rounds toward positive infinity with N decimal digits (positive N) or powers of ten (negative N).
• ceil(X, N, 'significant') rounds to N significant digits; N must be a positive integer.
• Logical inputs are promoted to doubles (false → 0, true → 1) before applying the ceiling operation.
• Character arrays are interpreted numerically (their Unicode code points) and return dense double tensors.
• Complex inputs are rounded component-wise: ceil(a + bi) = ceil(a) + i·ceil(b).
• Non-finite values (NaN, Inf, -Inf) propagate unchanged.
• Empty arrays return empty arrays of the appropriate shape.
• Appending 'like', prototype forces the result to match the residency of prototype (CPU or GPU). Prototypes must currently be numeric.

Does RunMat run ceil on the GPU?

When tensors already reside on the GPU, RunMat consults the active acceleration provider. If the provider implements the unary_ceil hook, ceil(X) executes entirely on the device and keeps tensors resident. When decimal or significant-digit rounding is requested—or when the provider lacks unary_ceil—RunMat gathers the tensor to host memory, applies the CPU implementation, and honours any 'like' GPU prototype by uploading the result back to the device. This maintains MATLAB-compatible behaviour while exposing GPU acceleration whenever it is available.

GPU memory and residency

A = [1.8 -0.2; 2.7 3.4];
proto = gpuArray(0);
G = ceil(A, 'like', proto);   % Result remains on the GPU
result = gather(G);

Expected output:

result =
    [ 2  0;
      3  4]

Examples

Rounding values up to the next integer

x = [-2.7, -0.3, 0, 0.8, 3.2];
y = ceil(x)

Expected output:

y = [-2, 0, 0, 1, 4]

Rounding a matrix up element-wise

A = [1.2 4.7; -3.4 5.0];
B = ceil(A)

Expected output:

B = [2 5; -3 5]

Rounding fractions upward in a tensor

t = reshape([-1.8, -0.2, 0.4, 1.1, 2.1, 3.6], [3, 2]);
up = ceil(t)

Expected output:

up =
    [-1  2;
      0  3;
      1  4]

Rounding up to two decimal places

temps = [21.452 19.991 22.501];
rounded = ceil(temps, 2)

Expected output:

rounded = [21.46 20 22.51]

Rounding to significant digits

measurements = [0.001234 12.3456 98765];
sig2 = ceil(measurements, 2, 'significant')

Expected output:

sig2 = [0.0013 13.0 99000]

Rounding complex numbers toward positive infinity

z = [1.2 + 2.1i, -0.2 - 3.9i];
result = ceil(z)

Expected output:

result = [2 + 3i, 0 - 3i]

Keeping GPU results on-device with unary_ceil

G = gpuArray([1.8 -0.2 0.0; -1.1 2.5 -3.4]);
up = ceil(G);
gather(up)

Expected output:

ans =
    [ 2  0  0;
     -1  3 -3]

Forcing GPU residency with a 'like' prototype

A = [1.8 -0.2; 2.7 3.4];
proto = gpuArray(0);
G = ceil(A, 'like', proto);   % Result remains on the GPU
result = gather(G)

Expected output:

result =
    [ 2  0;
      3  4]

Using ceil with coding agents

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

FAQ

Related Math functions

Open-source implementation

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

• View the source for ceil 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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