#version 450

#extension GL_EXT_control_flow_attributes : enable
#extension GL_EXT_shader_16bit_storage : require

#extension GL_EXT_shader_explicit_arithmetic_types_float16 : require
#extension GL_EXT_shader_explicit_arithmetic_types_int32 : require

#extension GL_KHR_shader_subgroup_basic : enable
#extension GL_KHR_memory_scope_semantics : enable
#extension GL_KHR_cooperative_matrix : enable

#include "types.glsl"
#include "flash_attn_base.glsl"

const uint32_t HSK_per_thread = HSK / D_split;
const uint32_t HSV_per_thread = HSV / D_split;

const uint32_t row_split = 4;
const uint32_t rows_per_thread = Br / row_split;
const uint32_t cols_per_iter = gl_WorkGroupSize.x / D_split / row_split;
const uint32_t cols_per_thread = Bc / cols_per_iter;


layout (binding = 0) readonly buffer Q {float data_q[];};
layout (binding = 0) readonly buffer QV4 {vec4 data_qv4[];};
layout (binding = 1) readonly buffer K {float16_t data_k[];};
layout (binding = 1) readonly buffer KV4 {f16vec4 data_kv4[];};
layout (binding = 2) readonly buffer V {float16_t data_v[];};
layout (binding = 2) readonly buffer VV4 {f16vec4 data_vv4[];};
layout (binding = 3) readonly buffer M {float16_t data_m[];};

// Store the output when doing grouped query attention.
// Rows index by Q's dimension 2, and the first N rows are valid.
D_TYPE perElemOpGqaStore(const in uint32_t r, const in uint32_t c, const in D_TYPE elem, const in uint32_t o_offset, const in uint32_t iq2, const in uint32_t N)
{
    uint32_t offset = (iq2 + r) * HSV + c;
    data_o[o_offset + offset] = D_TYPE(elem);
    return elem;
}

// These need to be supported N,M values for a MatBc x MatBr x 16 coopmatmuladd
const uint32_t MatBr = 16;
const uint32_t MatBc = 16;

shared FLOAT_TYPE tmpsh[gl_WorkGroupSize.x];
shared ACC_TYPEV4 tmpshv4[gl_WorkGroupSize.x];

const uint32_t qstride = HSK_pad / 4 + 2; // in units of f16vec4
shared f16vec4 Qf[Br * qstride];

// Avoid padding for hsk==256 to make it fit in 48KB shmem.
const uint32_t sfshstride = (HSK <= 128) ? (Br + 8) : Br;
shared ACC_TYPE sfsh[Bc * sfshstride];

const uint32_t kshstride = HSK_pad / 4 + 2; // in units of f16vec4
shared f16vec4 ksh[Bc * kshstride];

shared float slope[Br];

void main() {
#ifdef NEEDS_INIT_IQ_SHMEM
    init_iq_shmem(gl_WorkGroupSize);
#endif

    init_indices();

    const uint32_t tid = gl_LocalInvocationIndex;

    const uint32_t threads_per_rowgroup = gl_WorkGroupSize.x / row_split;
    const uint32_t row_tid = gl_LocalInvocationIndex / threads_per_rowgroup;
    const uint32_t d_tid = gl_LocalInvocationIndex % D_split;
    const uint32_t col_tid = (gl_LocalInvocationIndex % threads_per_rowgroup) / D_split;

#define tile_row(r) (row_tid * rows_per_thread + (r))

    // Zero-initialize shared memory for Q/K when HSK is not a multiple of 16 (HSK_pad > HSK).
    if ((HSK % 16) != 0) {
        [[unroll]] for (uint i = 0; i < Br * qstride; i += gl_WorkGroupSize.x) {
            if (i + tid < Br * qstride) {
                Qf[i + tid] = f16vec4(0);
            }
        }
        [[unroll]] for (uint i = 0; i < Bc * kshstride; i += gl_WorkGroupSize.x) {
            if (i + tid < Bc * kshstride) {
                ksh[i + tid] = f16vec4(0);
            }
        }
        barrier();
    }

    uint32_t q_offset = (iq2*p.nb02+iq3*p.nb03) / 4;

    [[unroll]] for (uint32_t idx = 0; idx < Br * HSK / 4; idx += gl_WorkGroupSize.x) {
        uint32_t d = (idx + tid) % (HSK / 4);
        uint32_t r = (idx + tid) / (HSK / 4);
        if (r < Br && d < HSK / 4 &&
            i * Br + r < N) {
            Qf[r * qstride + d] = f16vec4(data_qv4[q_offset / 4 + (i * Br + r) * q_stride / 4 + d] * p.scale);
        }
    }
    barrier();

    ACC_TYPEV4 Of[rows_per_thread][HSV_per_thread / 4];
    [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            Of[r][d] = ACC_TYPEV4(0.0);
        }
    }

    float Lf[rows_per_thread], Mf[rows_per_thread];

    // Use -FLT_MAX/2 rather than -inf to reduce the possibility of NaNs, e.g. when computing Mold-M.
    const float NEG_FLT_MAX_OVER_2 = uintBitsToFloat(0xFEFFFFFF);

    [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
        Lf[r] = 0;
        Mf[r] = NEG_FLT_MAX_OVER_2;
    }

    // ALiBi
    if (p.max_bias > 0.0f) {
        if (tid < Br) {
            uint r = tid;
            slope[r] = perElemOpComputeSlope(r, col_tid, ACC_TYPE(0), iq2);
        }
        barrier();
    } else {
        if (tid < Br) {
            uint r = tid;
            slope[r] = 1.0;
        }
        barrier();
    }

#if BLOCK_SIZE > 1
    uint32_t k_offset = (ik2*p.nb12 + ik3*p.nb13) / BLOCK_BYTE_SIZE;
    uint32_t v_offset = (iv2*p.nb22 + iv3*p.nb23) / BLOCK_BYTE_SIZE;
#else
    uint32_t k_offset = (ik2*p.nb12 + ik3*p.nb13) / 2;
    uint32_t v_offset = (iv2*p.nb22 + iv3*p.nb23) / 2;
#endif
    uint32_t m_offset = 0;
    if (p.nem2 != 1 || p.nem3 != 1) {
        m_offset = ((iq3 % p.nem3) * p.nem2 + (iq2 % p.nem2)) * p.nem1 * KV;
    }

    [[dont_unroll]]
    for (uint32_t j = start_j; j < end_j; ++j) {

        [[unroll]] for (uint32_t idx = 0; idx < Bc * HSK / 4; idx += gl_WorkGroupSize.x) {
            uint32_t d = (idx + tid) % (HSK / 4);
            uint32_t c = (idx + tid) / (HSK / 4);
            if (c < Bc && d < HSK / 4) {
                f16vec4 K_Tf = f16vec4(0);
                if (!KV_bounds_check || j * Bc + c < KV) {
#if BLOCK_SIZE > 1
                    uint coord = (j * Bc + c) * k_stride * BLOCK_SIZE + 4 * d;
                    uint ib = coord / BLOCK_SIZE;
                    uint iqs = (coord % BLOCK_SIZE);
                    K_Tf = f16vec4(dequantize4(ib, iqs, k_offset, BINDING_IDX_K));
#else
                    K_Tf = f16vec4(data_kv4[k_offset / 4 + (j * Bc + c) * k_stride / 4 + d]);
#endif
                }

                ksh[c * kshstride + d] = K_Tf;
            }
        }
        barrier();

        // K * Q^T -> S^T: Bc x HSK_pad * HSK_pad x Br -> Bc x Br
        // Bc split across workgroup (four subgroups), loop over HSK in chunks of 16: 16 x 16 * 16 x 16 -> 16 x 16
        // This is written transposed in order to allow for N being 8 if implementations need it
        coopmat<ACC_TYPE, gl_ScopeSubgroup, MatBc, MatBr, gl_MatrixUseAccumulator> SfMat = coopmat<ACC_TYPE, gl_ScopeSubgroup, MatBc, MatBr, gl_MatrixUseAccumulator>(0);
        coopmat<float16_t, gl_ScopeSubgroup, MatBc, 16, gl_MatrixUseA> KMat;
        coopmat<float16_t, gl_ScopeSubgroup, 16, MatBr, gl_MatrixUseB> QMat;

        for (uint32_t d = 0; d < HSK_pad / 16; ++d) {
            coopMatLoad(QMat, Qf, d * 16 / 4, qstride, gl_CooperativeMatrixLayoutColumnMajor);

            uint coord = (gl_SubgroupID * MatBc) * kshstride + d * 16 / 4;
            coopMatLoad(KMat, ksh, coord, kshstride, gl_CooperativeMatrixLayoutRowMajor);

            SfMat = coopMatMulAdd(KMat, QMat, SfMat);
        }

        uint coord = gl_SubgroupID * MatBc * sfshstride;
        coopMatStore(SfMat, sfsh, coord, sfshstride, gl_CooperativeMatrixLayoutRowMajor);
        barrier();

        if (p.logit_softcap != 0.0f) {
            [[unroll]] for (uint32_t idx = 0; idx < Bc * Br; idx += gl_WorkGroupSize.x) {
                uint32_t c = (idx + tid) / Br;
                uint32_t r = (idx + tid) % Br;
                if (idx + tid < Bc * Br || idx + gl_WorkGroupSize.x <= Bc * Br) {
                    sfsh[c * sfshstride + r] = ACC_TYPE(p.logit_softcap * tanh(sfsh[c * sfshstride + r]));
                }
            }
            barrier();
        }

        if ((p.mask_n_head_log2 & MASK_ENABLE_BIT) != 0) {
            bool nem1_bounds_check = !(p.gqa_ratio > 1) && (p.nem1 % Br) != 0;

            [[unroll]] for (uint32_t idx = 0; idx < Bc * Br; idx += gl_WorkGroupSize.x) {
                uint32_t c = (idx + tid) % Bc;
                uint32_t r = (idx + tid) / Bc;
                if (idx + tid < Bc * Br || idx + gl_WorkGroupSize.x <= Bc * Br) {
                    if ((!KV_bounds_check || j * Bc + c < KV) && (!nem1_bounds_check || i * Br + r < p.nem1)) {
                        sfsh[c * sfshstride + r] += ACC_TYPE(slope[r] * float(data_m[m_offset + (i * Br + r) * m_stride + (j * Bc + c)]));
                    }
                }
            }
            barrier();
        }

        float eMf[rows_per_thread];
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            float rowmaxf = NEG_FLT_MAX_OVER_2;
            [[unroll]] for (uint32_t c = 0; c < cols_per_thread; ++c) {
                if (KV_bounds_check && j * Bc + c * cols_per_iter + col_tid >= KV) {
                    continue;
                }
                rowmaxf = max(rowmaxf, float(sfsh[tile_row(r) + (c * cols_per_iter + col_tid) * sfshstride]));
            }
            float Moldf = Mf[r];

            // M = max(rowmax, Mold)
            // P = e^(S - M)
            // eM = e^(Mold - M)
            Mf[r] = max(rowmaxf, Moldf);
            eMf[r] = exp(Moldf - Mf[r]);
        }

        [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
            [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
                Of[r][d] = ACC_TYPE(eMf[r]) * Of[r][d];
            }
        }
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            Lf[r] = eMf[r]*Lf[r];
        }

        [[unroll]] for (uint32_t c = 0; c < cols_per_thread; ++c) {
            if (KV_bounds_check && j * Bc + c * cols_per_iter + col_tid >= KV) {
                continue;
            }
            float Pf[rows_per_thread];
            [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
                Pf[r] = exp(sfsh[tile_row(r) + (c * cols_per_iter + col_tid) * sfshstride] - Mf[r]);
                Lf[r] += Pf[r];
            }
            [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
#if BLOCK_SIZE > 1
                uint coord = (j * Bc + c * cols_per_iter + col_tid) * v_stride * BLOCK_SIZE + 4 * (d * D_split + d_tid);
                uint ib = coord / BLOCK_SIZE;
                uint iqs = (coord % BLOCK_SIZE);
                vec4 Vf = dequantize4(ib, iqs, v_offset, BINDING_IDX_V);
#else
                vec4 Vf = vec4(data_vv4[v_offset / 4 + (j * Bc + c * cols_per_iter + col_tid) * v_stride / 4 + d * D_split + d_tid]);
#endif
                [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
                    Of[r][d] += ACC_TYPE(Pf[r]) * ACC_TYPEV4(Vf);
                }
            }
        }

        barrier();
    }

    // reduce across threads

    float rowmaxf[rows_per_thread], eMf[rows_per_thread], Moldf[rows_per_thread];
    [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
        FLOAT_TYPE M = Mf[r];
        tmpsh[tid] = M;
        // Compute max across the row
        barrier();
        [[unroll]] for (int s = int(gl_WorkGroupSize.x / row_split) / 2; s >= D_split; s >>= 1) {
            M = max(M, tmpsh[tid ^ s]);
            barrier();
            tmpsh[tid] = M;
            barrier();
        }
        rowmaxf[r] = tmpsh[d_tid + row_tid * threads_per_rowgroup];
        barrier();
    }

    [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
        Moldf[r] = Mf[r];

        // M = max(rowmax, Mold)
        // eM = e^(Mold - M)
        Mf[r] = max(rowmaxf[r], Moldf[r]);
        eMf[r] = exp(Moldf[r] - Mf[r]);

        Lf[r] = eMf[r]*Lf[r];
    }

    [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
        FLOAT_TYPE L = Lf[r];
        tmpsh[tid] = L;
        // Compute sum across the row
        barrier();
        [[unroll]] for (int s = int(gl_WorkGroupSize.x / row_split) / 2; s >= D_split; s >>= 1) {
            L += tmpsh[tid ^ s];
            barrier();
            tmpsh[tid] = L;
            barrier();
        }
        Lf[r] = tmpsh[d_tid + row_tid * threads_per_rowgroup];
        barrier();
    }

    [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
        [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {

            Of[r][d] = ACC_TYPE(eMf[r]) * Of[r][d];
            tmpshv4[tid] = Of[r][d];

            barrier();
            [[unroll]] for (int s = int(gl_WorkGroupSize.x / row_split) / 2; s >= D_split; s >>= 1) {
                Of[r][d] += tmpshv4[tid ^ s];
                barrier();
                tmpshv4[tid] = Of[r][d];
                barrier();
            }
            Of[r][d] = tmpshv4[d_tid + row_tid * threads_per_rowgroup];
            barrier();
        }
    }

    // If there is split_k, then the split_k resolve shader does the final
    // division by L. Store the intermediate O value and per-row m and L values.
    if (p.k_num > 1) {
        uint32_t o_offset = HSV * p.ne1 * (split_k_index + iq3 * p.k_num);

        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            if (tile_row(r) < N) {
                [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
                    [[unroll]] for (uint32_t comp = 0; comp < 4; ++comp) {
                        perElemOpGqaStore(tile_row(r), 4*(d * D_split + d_tid) + comp, float(Of[r][d][comp]), o_offset, iq2, N);
                    }
                }
            }
        }

        o_offset = HSV * p.ne1 * p.ne3 * p.k_num + p.ne1 * (split_k_index + iq3 * p.k_num) * 2;
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            if (tile_row(r) < N) {
                perElemOpStoreCol0(tile_row(r), 0u, ACC_TYPE(Lf[r]), o_offset, iq2, N);
                perElemOpStoreCol0(tile_row(r), 0u, ACC_TYPE(Mf[r]), o_offset + p.ne1, iq2, N);
            }
        }

        return;
    }

    if ((p.mask_n_head_log2 & SINK_ENABLE_BIT) != 0) {
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            float sink = perElemOpGetSink(tile_row(r), 0u, ACC_TYPE(0), iq2);

            float ms = 1.0f;
            float vs = 1.0f;

            if (sink > Mf[r]) {
                ms = exp(Mf[r] - sink);

                [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
                    Of[r][d] *= ACC_TYPE(ms);
                }
            } else {
                vs = exp(sink - Mf[r]);
            }

            Lf[r] = Lf[r]*ms + vs;
        }
    }

    float Lfrcp[rows_per_thread];
    [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
        Lfrcp[r] = 1.0 / Lf[r];
    }

    [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            Of[r][d] *= ACC_TYPE(Lfrcp[r]);
#if defined(ACC_TYPE_MAX)
            Of[r][d] = clamp(Of[r][d], -ACC_TYPE_MAX, ACC_TYPE_MAX);
#endif
        }
    }

    uint32_t o_offset = iq3*p.ne2*p.ne1*HSV;

    if (p.gqa_ratio > 1) {
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            if (tile_row(r) < N) {
                [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
                    [[unroll]] for (uint32_t comp = 0; comp < 4; ++comp) {
                        perElemOpGqaStore(tile_row(r), 4*(d * D_split + d_tid) + comp, float(Of[r][d][comp]), o_offset, iq2, N);
                    }
                }
            }
        }
    } else {
        [[unroll]] for (uint32_t r = 0; r < rows_per_thread; ++r) {
            if (i * Br + tile_row(r) < N) {
                [[unroll]] for (uint32_t d = 0; d < HSV_per_thread / 4; ++d) {
                    [[unroll]] for (uint32_t comp = 0; comp < 4; ++comp) {
                        data_o[o_offset + iq2 * HSV + (i * Br + tile_row(r)) * p.ne1 * HSV + 4*(d * D_split + d_tid) + comp] = D_TYPE(Of[r][d][comp]);
                    }
                }
            }
        }
    }
}
