On the oneAPI backend, af::max(val, idx, in, 1) and af::min(val, idx, in, 1) (indexed reductions along dim 1) return wrong values and indices when the array has few rows: only part of each row is reduced.

Description

• Official Windows installer, ArrayFire v3.10.0 (build 492718b).
• Backend: oneAPI only. The same binary on the same GPU gives correct results with the OpenCL backend, and with the CPU backend. CUDA / OpenCL / CPU on an NVIDIA machine are also correct.
• Only the indexed form is affected. af::max(in, 1) (no indices) is correct, and the indexed call along dim 0 is correct.
• Reproducible every run.
• Workaround: transpose (or af::reorder) so the reduced dimension is dim 0, call af::max(val, idx, in, 0), and transpose back.
• Expected: the same values and indices as af::max(val, idx, in.T(), 0) transposed back, as on the other backends.

Related but different: #3656 (wrong location for a subarray input, on CUDA/OpenCL/CPU). Here the input is a plain, contiguous array, and only oneAPI is affected.

Reproducible Code and/or Steps

#include <arrayfire.h>
#include <cstdio>

int main() {
    af::setBackend(AF_BACKEND_ONEAPI);
    af::info();
    // [3, 5], column-major. Row maxima are in columns 1, 3 and 4.
    const float v[15] = {0.0555f, 0.5535f, 0.2385f,
                         0.8969f, 0.3002f, 0.3137f,
                         0.0944f, 0.0550f, 0.0022f,
                         0.2531f, 0.7665f, 0.0864f,
                         0.3456f, 0.1136f, 0.9150f};
    af::array x(3, 5, v);
    af::array val, idx;
    af::max(val, idx, x, 1);
    af_print(val);
    af_print(idx);  // oneAPI: 1 0 1 (values 0.8969 0.5535 0.3137); expected 1 3 4 (0.8969 0.7665 0.9150)
    return 0;
}

A wider check (randn arrays, dim 1 compared with dim 0 of the transpose), oneAPI device 0:

With opencl or cpu selected instead, every row is ok on the same machine.

System Information

1. ArrayFire v3.10.0 (build 492718b), official Windows installer.
2. Intel Core i5-1135G7 with Intel Iris Xe Graphics, driver 32.0.101.7088 (2026-06-17). Windows 11 Pro Education, build 26300.
3. af::info():

ArrayFire v3.10.0 (oneAPI, 64-bit Windows, build 492718b5a)
[0] Intel(R) OpenCL Graphics: Intel(R) Iris(R) Xe Graphics, 7129 MB (fp16 )
-1- Intel(R) OpenCL: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz, 16126 MB (fp64 fp16 )