/*
 * bench_implicit_v2.cu — A/B benchmark of implicit_gemm_conv (v1, FP32 in)
 * vs implicit_gemm_conv_v2 (16-warp 128x128x32, FP16 in, cp.async).
 *
 * Pre-converts X from FP32 to FP16 outside the timed loop so we are
 * comparing the conv work alone, apples-to-apples.
 *
 * Build:
 *   nvcc -arch=sm_86 -O2 -std=c++17 -o bench_implicit_v2 bench_implicit_v2.cu \
 *        -lcuda -I../../kernels/_common
 */

#include <cstdio>
#include <cstdlib>
#include <vector>
#include <cmath>
#include <cuda.h>
#include <cuda_fp16.h>

#include "../../_common/bench.h"
#include "../../_common/check.h"

#define BM_V1 64
#define BN_V1 64
#define BK_V1 16
#define BM_V2 128
#define BN_V2 128
#define BK_V2 32
#define PAD   8

#define BLOCK_THREADS_V1 128
#define BLOCK_THREADS_V2 512

static void cpu_conv2d_nhwc(
    const float *X, const float *W_row, float *Y,
    int N, int H, int Wd, int Cin, int Cout
) {
    for (int n = 0; n < N; n++)
        for (int h = 0; h < H; h++)
            for (int w = 0; w < Wd; w++)
                for (int co = 0; co < Cout; co++) {
                    double acc = 0.0;
                    for (int kh = 0; kh < 3; kh++)
                        for (int kw = 0; kw < 3; kw++) {
                            int hi = h + kh - 1, wi = w + kw - 1;
                            if (hi < 0 || hi >= H || wi < 0 || wi >= Wd) continue;
                            for (int ci = 0; ci < Cin; ci++) {
                                acc += (double)X[(size_t)n*H*Wd*Cin + hi*Wd*Cin + wi*Cin + ci]
                                     * (double)W_row[(size_t)co*9*Cin + (kh*3+kw)*Cin + ci];
                            }
                        }
                    Y[(size_t)n*H*Wd*Cout + h*Wd*Cout + w*Cout + co] = (float)acc;
                }
}

// Pre-cast kernel: FP32 -> FP16 element-wise.
__global__ void cast_f32_to_f16(const float *src, __half *dst, size_t n) {
    size_t i = blockIdx.x * blockDim.x + threadIdx.x;
    if (i < n) dst[i] = __float2half(src[i]);
}

// Reshape weights [Cout, kH, kW, Cin] (FP32) -> [Cin*kH*kW, Cout] (FP16)
static void reshape_weights(const float *Wd, __half *Wt,
                            int Cout, int Cin, int kH, int kW) {
    int K = Cin * kH * kW;
    for (int k = 0; k < K; k++) {
        int cin = k / (kH * kW);
        int kp  = k % (kH * kW);
        int kh = kp / kW, kw = kp % kW;
        for (int c = 0; c < Cout; c++) {
            float v = Wd[(size_t)c * kH * kW * Cin + (kh*kW + kw)*Cin + cin];
            Wt[(size_t)k * Cout + c] = __float2half(v);
        }
    }
}

struct Result { double ms; double gflops; };

int main(int argc, char **argv) {
    CHECK_CU(cuInit(0));
    CUdevice dev; CHECK_CU(cuDeviceGet(&dev, 0));
    CUcontext ctx; CHECK_CU(cuDevicePrimaryCtxRetain(&ctx, dev));
    CHECK_CU(cuCtxSetCurrent(ctx));
    char devname[256]; CHECK_CU(cuDeviceGetName(devname, sizeof(devname), dev));
    printf("Device: %s\n\n", devname);

    CUmodule mod_v1, mod_v2;
    CUfunction fn_v1, fn_v2;
    CHECK_CU(cuModuleLoad(&mod_v1, "conv2d_implicit_gemm.sm_86.cubin"));
    CHECK_CU(cuModuleLoad(&mod_v2, "conv2d_implicit_gemm_v2.sm_86.cubin"));
    CHECK_CU(cuModuleGetFunction(&fn_v1, mod_v1, "implicit_gemm_conv"));
    CHECK_CU(cuModuleGetFunction(&fn_v2, mod_v2, "implicit_gemm_conv_v2"));

    // v1 dynamic smem
    int A1_stride = BK_V1 + PAD, B1_stride = BN_V1 + PAD;
    size_t smem_v1 = (BM_V1*A1_stride + BK_V1*B1_stride) * sizeof(__half)
                   + (3*BM_V1 + 3*BK_V1) * sizeof(int);
    CHECK_CU(cuFuncSetAttribute(fn_v1,
        CU_FUNC_ATTRIBUTE_MAX_DYNAMIC_SHARED_SIZE_BYTES, (int)smem_v1));

    struct Shape { int N; int H; int W; int C; const char *label; };
    Shape shapes[] = {
        { 1,  64, 32, 32, "N=1  C=64  32x32   (Obs BB regime)" },
        { 1, 128, 32, 32, "N=1  C=128 32x32" },
        { 1, 256, 32, 32, "N=1  C=256 32x32" },
        { 1, 512, 16, 16, "N=1  C=512 16x16" },
        { 4, 128, 32, 32, "N=4  C=128 32x32" },
        { 4, 256, 32, 32, "N=4  C=256 32x32" },
        { 4, 512, 16, 16, "N=4  C=512 16x16" },
        { 8, 256, 32, 32, "N=8  C=256 32x32" },
    };
    int n_shapes = sizeof(shapes) / sizeof(Shape);

    printf("%-32s %12s %12s %12s %12s %8s\n",
           "shape (single conv)", "v1 ms", "v1 GFLOPS", "v2 ms", "v2 GFLOPS", "speedup");
    printf("%-32s %12s %12s %12s %12s %8s\n",
           "-------------------", "-----", "---------", "-----", "---------", "-------");

    int kH = 3, kW = 3, pad = 1;
    int passed = 0, total = 0;
    double sp_sum_log = 0.0;

    for (int s = 0; s < n_shapes; s++) {
        int N = shapes[s].N, H = shapes[s].H, Wd = shapes[s].W, C = shapes[s].C;
        int Cin = C, Cout = C;
        size_t elems = (size_t)N * H * Wd * C;
        size_t weights = (size_t)Cout * 9 * Cin;
        int M = N * H * Wd;
        int K_dim = Cin * 9;

        // Skip if v2 BN doesn't divide Cout nicely (require multiple)
        // (kernel handles partial tiles but bench wants aligned for cleanliness)

        std::vector<float> hX(elems), hW(weights), hRef(elems);
        for (size_t i = 0; i < elems;   i++) hX[i] = ((i*17+3)%11)/11.0f - 0.45f;
        for (size_t i = 0; i < weights; i++) hW[i] = (((i*23+5)%13)/13.0f - 0.45f) * 0.05f;

        // Reference (CPU) for first 2 small shapes only (cost grows fast).
        bool do_check = (elems * (size_t)9 * Cin <= 5e7);
        if (do_check) cpu_conv2d_nhwc(hX.data(), hW.data(), hRef.data(),
                                       N, H, Wd, Cin, Cout);

        std::vector<__half> hWt((size_t)K_dim * Cout);
        reshape_weights(hW.data(), hWt.data(), Cout, Cin, kH, kW);

        CUdeviceptr dX_f32, dX_f16, dW, dY1, dY2;
        CHECK_CU(cuMemAlloc(&dX_f32, elems * sizeof(float)));
        CHECK_CU(cuMemAlloc(&dX_f16, elems * sizeof(__half)));
        CHECK_CU(cuMemAlloc(&dW,     (size_t)K_dim * Cout * sizeof(__half)));
        CHECK_CU(cuMemAlloc(&dY1,    elems * sizeof(float)));
        CHECK_CU(cuMemAlloc(&dY2,    elems * sizeof(float)));
        CHECK_CU(cuMemcpyHtoD(dX_f32, hX.data(),  elems * sizeof(float)));
        CHECK_CU(cuMemcpyHtoD(dW,     hWt.data(), (size_t)K_dim * Cout * sizeof(__half)));

        // Pre-cast X to FP16 (NOT timed; happens once outside the bench loop).
        {
            int threads = 256;
            int blocks  = (int)((elems + threads - 1) / threads);
            cast_f32_to_f16<<<blocks, threads>>>(
                (const float*)dX_f32, (__half*)dX_f16, elems);
            CHECK_CU(cuCtxSynchronize());
        }

        // ---- v1 launch (FP32 input) ----
        int gv1_m = (M + BM_V1 - 1) / BM_V1;
        int gv1_n = (Cout + BN_V1 - 1) / BN_V1;
        auto launch_v1 = [&]() {
            void *args[] = { &dX_f32, &dW, &dY1, &N, &H, &Wd, &Cin,
                             &kH, &kW, &pad, &H, &Wd, &M, &K_dim, &Cout };
            CHECK_CU(cuLaunchKernel(fn_v1, gv1_m, gv1_n, 1,
                                    BLOCK_THREADS_V1, 1, 1,
                                    (unsigned)smem_v1, 0, args, 0));
        };

        // ---- v2 launch (FP16 input) ----
        int gv2_m = (M + BM_V2 - 1) / BM_V2;
        int gv2_n = (Cout + BN_V2 - 1) / BN_V2;
        auto launch_v2 = [&]() {
            void *args[] = { &dX_f16, &dW, &dY2, &N, &H, &Wd, &Cin,
                             &kH, &kW, &pad, &H, &Wd, &M, &K_dim, &Cout };
            CHECK_CU(cuLaunchKernel(fn_v2, gv2_m, gv2_n, 1,
                                    BLOCK_THREADS_V2, 1, 1, 0, 0, args, 0));
        };

        // Warmup
        for (int i = 0; i < 5; i++) { launch_v1(); launch_v2(); }
        CHECK_CU(cuCtxSynchronize());

        // Correctness check
        bool ok_v2 = true;
        if (do_check) {
            std::vector<float> hY2(elems);
            launch_v2();
            CHECK_CU(cuCtxSynchronize());
            CHECK_CU(cuMemcpyDtoH(hY2.data(), dY2, elems * sizeof(float)));
            float max_abs = 0, max_rel = 0;
            int n_bad = 0;
            for (size_t i = 0; i < elems; i++) {
                float a = std::fabs(hY2[i] - hRef[i]);
                float r = (std::fabs(hRef[i]) > 1e-6f) ? a / std::fabs(hRef[i]) : 0;
                if (a > max_abs) max_abs = a;
                if (r > max_rel) max_rel = r;
                if (a > 0.1f && r > 0.1f) n_bad++;
            }
            ok_v2 = (n_bad < (int)elems / 1000);
            if (!ok_v2) {
                printf("[v2 CHECK FAIL %s: max_abs=%.3e max_rel=%.3e n_bad=%d]\n",
                       shapes[s].label, max_abs, max_rel, n_bad);
            }
        }

        // Time v1
        BenchTimer t;
        const int iters = 30;
        t.start();
        for (int i = 0; i < iters; i++) launch_v1();
        float ms_v1 = t.stop_ms() / iters;
        // Time v2
        t.start();
        for (int i = 0; i < iters; i++) launch_v2();
        float ms_v2 = t.stop_ms() / iters;

        double flops = 2.0 * M * Cout * K_dim;
        double gf_v1 = flops / (ms_v1 / 1000.0) / 1e9;
        double gf_v2 = flops / (ms_v2 / 1000.0) / 1e9;
        double speedup = ms_v1 / ms_v2;

        printf("%-32s %12.3f %12.0f %12.3f %12.0f %7.3fx%s\n",
               shapes[s].label, ms_v1, gf_v1, ms_v2, gf_v2,
               speedup, ok_v2 ? "" : " [FAIL]");

        if (ok_v2) { passed++; sp_sum_log += std::log(speedup); }
        total++;

        cuMemFree(dX_f32); cuMemFree(dX_f16); cuMemFree(dW);
        cuMemFree(dY1); cuMemFree(dY2);
    }

    if (passed > 0) {
        printf("\nGeomean speedup across %d passing shapes: %.3fx\n",
               passed, std::exp(sp_sum_log / passed));
    }
    return 0;
}