#version 450

#ifdef FLOAT16
#extension GL_EXT_shader_explicit_arithmetic_types_float16 : require
#endif
#extension GL_EXT_shader_explicit_arithmetic_types_int32 : require

#extension GL_EXT_null_initializer : enable

#include "mul_mat_vec_base.comp"

layout(local_size_x_id = 0, local_size_y = 1, local_size_z = 1) in;

layout (constant_id = 0) const uint BLOCK_SIZE = 32;
layout (constant_id = 1) const uint NUM_ROWS = 1;

uint a_offset, b_offset, d_offset, y_offset;

shared FLOAT_TYPE tmpsh[NUM_ROWS][BLOCK_SIZE];

void iter(inout FLOAT_TYPE temp[NUM_ROWS], const uint first_row, const uint num_rows, const uint tid, const uint i, bool lastiter)
{
    const uint col = i*BLOCK_SIZE + 2*tid;
    const uint iqs = (col%QUANT_K)/QUANT_R; // quant index
    const uint iybs = col - col%QUANT_K; // y block start index

    // Check if the second of the pair of elements is OOB, and don't fetch B or
    // accumulate it. We still fetch a pair of elements for A, which is fine for
    // quantized formats since they'll be within the same block. We should
    // probably skip fetching the second element for F16/F32, but as of now we
    // still do.
    const bool OOB = lastiter && (iybs + iqs + y_offset >= p.ncols);

    FLOAT_TYPE b0 = 0, b1 = 0;
    b0 = FLOAT_TYPE(data_b[b_offset + iybs + iqs]);
    if (!OOB) {
        b1 = FLOAT_TYPE(data_b[b_offset + iybs + iqs + y_offset]);
    }
    [[unroll]] for (uint n = 0; n < num_rows; ++n) {
        const uint ib = ((first_row + n)*p.ncols + col)/QUANT_K; // block index

        const vec2 v = dequantize(ib, iqs, a_offset);

        // matrix multiplication
        temp[n] = fma(FLOAT_TYPE(v.x), b0, temp[n]);
        if (!OOB) {
            temp[n] = fma(FLOAT_TYPE(v.y), b1, temp[n]);
        }
    }
}

void compute_outputs(const uint32_t first_row, const uint32_t num_rows) {
    const uint tid = gl_LocalInvocationID.x;

    get_offsets(a_offset, b_offset, d_offset);
    a_offset /= QUANT_K;

    y_offset = QUANT_R == 1 ? 1 : QUANT_K/2;

    FLOAT_TYPE temp[NUM_ROWS] = {};

    const int unroll_count = 8;

    const uint num_iters = (p.ncols >= 2*tid) ? ((p.ncols - 2*tid + BLOCK_SIZE - 1) / BLOCK_SIZE) : 0;
    const uint unrolled_iters = num_iters & ~(2*unroll_count - 1);

    uint i = 0;
    while (i < unrolled_iters) {
        // Manually partially unroll the loop
        [[unroll]] for (uint k = 0; k < unroll_count; ++k) {
            iter(temp, first_row, num_rows, tid, i, false);
            i += 2;
        }
    }
    while (i < num_iters) {
        iter(temp, first_row, num_rows, tid, i, true);
        i += 2;
    }

    // sum up partial sums and write back result
    [[unroll]] for (uint n = 0; n < num_rows; ++n) {
        tmpsh[n][tid] = temp[n];
    }
    barrier();
    [[unroll]] for (uint s = BLOCK_SIZE/2; s > 0; s >>= 1) {
        if (tid < s) {
            [[unroll]] for (uint n = 0; n < num_rows; ++n) {
                tmpsh[n][tid] += tmpsh[n][tid + s];
            }
        }
        barrier();
    }
    if (tid == 0) {
        [[unroll]] for (uint n = 0; n < num_rows; ++n) {
            data_d[d_offset + first_row + n] = D_TYPE(tmpsh[n][0]);
        }
    }
}

void main() {
    const uint first_row = NUM_ROWS * (gl_WorkGroupID.x + gl_NumWorkGroups.x * gl_WorkGroupID.z);

    // do NUM_ROWS at a time, unless there aren't enough remaining rows
    if (first_row + NUM_ROWS <= p.stride_d) {
        compute_outputs(first_row, NUM_ROWS);
    } else {
        compute_outputs(first_row, p.stride_d - first_row);
    }
}