#version 450

#define LABEL(_idx) values[_idx]

layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
layout(binding = 0) buffer Binding { 
    int values[];
};

int findRoot(uint index) {
    int v = atomicAdd(LABEL(index), 0);
    if (v < 0) {
        return v;
    }
    int w = int(index);
    while (v != w) {
        w = v;
        v = atomicAdd(LABEL(v), 0);
    }
    return v;
}

void main() {
    uint id = gl_GlobalInvocationID.x;
    int v = findRoot(id);
    if (v >= 0) {
        atomicExchange(LABEL(id), v);
    }
}