fix — Round values toward zero in MATLAB and RunMat.
fix(X) removes the fractional part of each element by rounding toward zero. Positive values behave like floor, negative values behave like ceil, and complex values are processed component-wise. Input coercions and array-shape behavior follow MATLAB semantics.
Syntax
Y = fix(X)Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
X | Any | Yes | — | Numeric, logical, or complex input array. |
Returns
| Name | Type | Description |
|---|---|---|
Y | NumericArray | Rounded values toward zero. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:fix:InvalidInput | Input cannot be interpreted as numeric, logical, or complex data. | fix: invalid input |
RunMat:fix:Internal | Internal tensor conversion or allocation failed. | fix: internal error |
How fix works
fixrounds positive inputs down toward zero and negative inputs up toward zero.- All eight integer classes are exact class-preserving identity operations. Logical inputs are promoted to double before rounding.
- Complex numbers are rounded component-wise (
fix(a + bi) = fix(a) + i·fix(b)), matching MATLAB. NaN,Inf, and-Infpropagate unchanged.- Character arrays are treated as their numeric code points and return dense double tensors.
- Empty arrays return empty arrays with identical shape.
Does RunMat run fix on the GPU?
Resident integer tensors are returned as exact identity operations without floating conversion or a new allocation. Floating tensors use the owning provider's optional unary_fix hook when available; otherwise RunMat gathers, computes with matching host precision, and uploads the result back to that same provider. Logical tensors follow the promotion-to-double path and are likewise restored to the owner.
GPU memory and residency
G = gpuArray(linspace(-2.4, 2.4, 6));
truncGpu = fix(G);
hostValues = gather(truncGpu);Expected output:
hostValues = [-2 -1 0 0 1 2];Examples
Truncating positive and negative values toward zero
values = [-3.7 -2.4 -0.6 0 0.6 2.4 3.7];
truncated = fix(values)Expected output:
truncated = [-3 -2 0 0 0 2 3]Removing fractional parts from a matrix
A = [1.9 4.1; -2.8 0.5];
B = fix(A)Expected output:
B = [1 4; -2 0]Keeping GPU residency when kernels are available
G = gpuArray(linspace(-2.4, 2.4, 6));
truncGpu = fix(G);
hostValues = gather(truncGpu)Expected output:
hostValues = [-2 -1 0 0 1 2]Dropping fractional parts of complex numbers
z = [1.9 + 2.6i, -3.4 - 0.2i];
fixed = fix(z)Expected output:
fixed = [1 + 2i, -3 + 0i]Converting character arrays to truncated numeric codes
letters = ['A' 'B' 'C'];
codes = fix(letters)Expected output:
codes = [65 66 67]Using fix with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how fix changes the result.
Run a small fix example, explain the result, then change one input and compare the output.
FAQ
How is fix different from floor and ceil?⌄
fix always rounds toward zero. Positive numbers behave like floor, negatives behave like ceil. Use floor or ceil when you specifically want to round toward negative or positive infinity.
What happens to existing integers?⌄
Typed integer inputs preserve their exact class, shape, and values. Logical inputs are different: they promote to double values of 0 or 1.
Does fix change NaN or Inf values?⌄
No. NaN, Inf, and -Inf propagate unchanged.
How are complex numbers handled?⌄
fix rounds the real and imaginary components independently, exactly like MATLAB.
Will fix stay on the GPU?⌄
Yes. Resident integer inputs retain their original handle. Floating and logical fallback results are uploaded back to the input's owning provider when a native kernel is unavailable.
Related Math functions
Elementwise
abs · angle · bsxfun · complex · conj · double · erf · erfcinv · exp · expm1 · factorial · flintmax · gamma · gammaln · heaviside · hypot · idivide · imag · intmax · intmin · ldivide · log · log10 · log1p · log2 · minus · nextpow2 · plus · pow2 · power · rdivide · real · realmax · realmin · realsqrt · rescale · sign · single · sqrt · swapbytes · times · typecast · uint16 · uint32 · uint8
Trigonometry
acos · acosh · asin · asinh · atan · atan2 · atanh · cos · cosd · cosh · cospi · deg2rad · pol2cart · rad2deg · sin · sind · sinh · sinpi · tan · tand · tanh
Reduction
all · any · bounds · cummax · cummin · cumprod · cumsum · cumtrapz · diff · gradient · max · maxk · mean · median · min · mink · movmax · movmean · movmedian · movmin · movprod · movstd · movsum · movvar · nnz · prod · rms · std · sum · trapz · var
Structure
bandwidth · isdiag · ishermitian · issymmetric · istril · istriu · symrcm
Signal
blackman · butter · buttord · cheb2ord · conv · conv2 · deconv · downsample · envelope · filter · filtfilt · fir1 · freqz · gauspuls · hamming · hann · hilbert · periodogram · pulstran · pwelch · rectpuls · resample · sawtooth · sinc · spectrogram · square · tripuls · unwrap · upsample · zplane
Optim
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Ops
cross · ctranspose · dot · mldivide · mpower · mrdivide · mtimes · pagemtimes · pagetranspose · trace · transpose
Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how fix is executed, line by line, in Rust.
- View the source for fix in Rust on GitHub
- Learn how the RunMat runtime works
- Found a bug? Open an issue with a minimal reproduction.
About RunMat
RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.
- RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
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