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@group(0) @binding(0)
#ifdef VEC4
var<storage, read_write> src: array<vec4<f32>>;
#define VEC_SIZE 4
#else
var<storage, read_write> src: array<f32>;
#define VEC_SIZE 1
#endif
@group(0) @binding(1)
var<storage, read_write> dst: array<i32>;
struct Params {
offset_src: u32, // in elements
offset_dst: u32, // in elements
ne0: u32,
};
@group(0) @binding(2)
var<uniform> params: Params;
const FLOAT_MIN: f32 = -1.0e9;
struct Pair {
value: f32,
index: i32
};
var<workgroup> shared_max: array<Pair, WG_SIZE>;
@compute @workgroup_size(WG_SIZE)
fn main(@builtin(workgroup_id) wid: vec3<u32>,
@builtin(local_invocation_id) lid: vec3<u32>) {
let row_idx = params.offset_src + wid.x * params.ne0;
var local_pair = Pair(FLOAT_MIN, -1);
#ifdef VEC4
for (var col = lid.x; col < params.ne0/VEC_SIZE; col += WG_SIZE) {
let vec_val = src[row_idx / VEC_SIZE + col];
for (var v = 0u; v < VEC_SIZE; v++) {
let val = vec_val[v];
if (val >= local_pair.value) {
local_pair = Pair(val, i32(col * VEC_SIZE + v));
}
}
}
#else
for (var col = lid.x; col < params.ne0; col += WG_SIZE) {
if (src[row_idx + col] >= local_pair.value) {
local_pair = Pair(src[row_idx + col], i32(col));
}
}
#endif
shared_max[lid.x] = local_pair;
workgroupBarrier();
var offset: u32 = WG_SIZE >> 1;
while (offset > 0) {
if (lid.x < offset) {
let a = shared_max[lid.x];
let b = shared_max[lid.x + offset];
if (b.value > a.value) {
shared_max[lid.x] = b;
} else if (b.value == a.value && b.index > a.index) {
shared_max[lid.x] = b;
}
}
workgroupBarrier();
offset >>= 1;
}
if (lid.x == 0u) {
dst[params.offset_dst + wid.x] = shared_max[0].index;
}
}
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