Perform reduction on array

[fritzio]

Is there a way to perform a reduction, such as the maximum oder minimum value, on a wp.array? I was thinking something like

rho = wp.zeros(1024, dtype=wp.float32)
# ... fill rho with values
rho_max = wp.max(rho)

[christophercrouzet]

Hi @fritzio!

Yes, it's possible with wp.atomic_min() and wp.atomic_max(). These can be called from within a kernel, for example:

#!/usr/bin/env python3

import math

import warp as wp


@wp.kernel
def compute_min_max(
    values: wp.array(dtype=float),
    out: wp.array(dtype=float),
):
    tid = wp.tid()
    wp.atomic_min(out, 0, values[tid])
    wp.atomic_max(out, 1, values[tid])


def run():
    values = wp.array((5, -3, 8, -2, 7, 4), dtype=float)
    out = wp.array((+math.inf, -math.inf), dtype=float)
    wp.launch(compute_min_max, dim=values.shape, inputs=(values,), outputs=(out,))
    print(out.numpy())


if __name__ == "__main__":
    run()

[fritzio]

Ah, great - thank you for the working example :)