#version 440 core
layout(std430) buffer;

layout(set=0, binding=0) writeonly buffer pointoffsetSum{
    highp uint data[];
} uPointoffsetSum;


layout(set=0, binding=1) readonly buffer pointoffset{
    highp uint data[];
} uPointoffset;

layout(set=0, binding=2) uniform constBuffer {
    ivec4 point; // point size
} uConstant;

shared uint local_sum[256];

#define UNIT 3
#define LOCAL_SIZE 8
layout (local_size_x = LOCAL_SIZE, local_size_y = 1, local_size_z = 1) in;
void main()
{
	int tId = int(gl_LocalInvocationID.x);
    int size = uConstant.point.x;
    int curOffset = 0;
    uint threadBuffer[UNIT];
    while (curOffset < size) {
        int sta = tId * UNIT + curOffset;
        int fin = min(sta + UNIT, size);
        for (int i=sta; i<fin; ++i) {
            int lpos = i - sta;
            threadBuffer[lpos] = uPointoffset.data[i];
        }
        for (int i=sta+1; i<fin; ++i) {
            int lpos = i - sta;
            threadBuffer[lpos] = threadBuffer[lpos] + threadBuffer[lpos-1];
        }
        local_sum[tId] = threadBuffer[fin-sta-1];
        barrier();
        if (fin > sta) {
            uint sum = 0;
            for (int i=0; i<tId; ++i) {
                sum += local_sum[i];
            }
            for (int i=sta; i<fin; ++i) {
                int lpos = i - sta;
                uPointoffsetSum.data[i] = threadBuffer[lpos] + sum;
            }
        }
        curOffset += LOCAL_SIZE * UNIT;
    }
}