gemv_utils.h

#pragma once

#include <algorithm>
#include <functional>
#include <hip/hip_bfloat16.h>
#include <hip/hip_runtime.h>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>

// --------------------------------------------------------------------------------
// Error Handling
// --------------------------------------------------------------------------------

inline void checkHipErrors(hipError_t result) {
  if (result != hipSuccess) {
    std::cerr << "HIP Error: " << hipGetErrorString(result) << std::endl;
    exit(1);
  }
}

// --------------------------------------------------------------------------------
// Command Line Parsing
// --------------------------------------------------------------------------------

inline char *getCmdOption(char **begin, char **end, const std::string &option) {
  char **itr = std::find(begin, end, option);
  if (itr != end && ++itr != end) {
    return *itr;
  }
  return 0;
}

// --------------------------------------------------------------------------------
// CPU Reference & Verification
// --------------------------------------------------------------------------------

inline void gemv_cpu(int M, int K, float alpha, const hip_bfloat16 *h_A,
                     int lda, const hip_bfloat16 *h_x, hip_bfloat16 *h_y) {
  for (int m = 0; m < M; ++m) {
    float sum = 0.0f;
    for (int k = 0; k < K; ++k) {
      float val_a = static_cast<float>(h_A[m * lda + k]);
      float val_x = static_cast<float>(h_x[k]);
      sum += val_a * val_x;
    }
    h_y[m] = hip_bfloat16(alpha * sum);
  }

  return;
}

inline bool verify_result(int M, const hip_bfloat16 *h_y_gpu,
                          const hip_bfloat16 *h_y_ref) {
  float max_diff = 0.0f;
  int err_count = 0;
  for (int i = 0; i < M; ++i) {
    float gpu_val = static_cast<float>(h_y_gpu[i]);
    float cpu_val = static_cast<float>(h_y_ref[i]);
    float diff = std::abs(gpu_val - cpu_val);

    // bfloat16 的精度有限，容忍度需要稍大一点
    // 同时也考虑数值大小，这里使用简单的绝对误差 + 相对误差阈值
    if (diff > 0.1f && diff / (std::abs(cpu_val) + 1e-6) > 0.01) {
      if (err_count < 5) {
        std::cerr << "Mismatch at index " << i << ": GPU=" << gpu_val
                  << ", CPU=" << cpu_val << ", Diff=" << diff << std::endl;
      }
      err_count++;
    }
    max_diff = std::max(max_diff, diff);
  }

  if (err_count > 0) {
    std::cerr << "Total mismatches: " << err_count << ", Max Diff: " << max_diff
              << std::endl;
    return false;
  }
  return true;
}

// --------------------------------------------------------------------------------
// Benchmark Framework
// --------------------------------------------------------------------------------

// 定义统一的 Kernel Launcher 签名
using KernelLauncher =
    std::function<void(int M, int K, float alpha, const hip_bfloat16 *A,
                       int lda, const hip_bfloat16 *x, hip_bfloat16 *y)>;

struct KernelCase {
  std::string name;
  KernelLauncher func;
};

inline void run_benchmark(const std::vector<KernelCase> &cases, int M, int K,
                          float alpha, const hip_bfloat16 *A, int lda,
                          const hip_bfloat16 *x, hip_bfloat16 *y,
                          bool do_verify) {

  std::cout << "GEMV Benchmarks" << std::endl;

  hipEvent_t start, stop;
  checkHipErrors(hipEventCreate(&start));
  checkHipErrors(hipEventCreate(&stop));

  // 准备 verification 数据
  std::vector<hip_bfloat16> h_y_ref(M);
  std::vector<hip_bfloat16> h_y_gpu(M);
  std::vector<hip_bfloat16> h_A(M * K);
  std::vector<hip_bfloat16> h_x(K);

  if (do_verify) {
    std::cout << "Verifying results against CPU reference..." << std::endl;
    // 把 A 和 x 拷回 host 端计算
    checkHipErrors(hipMemcpy(h_A.data(), A, M * K * sizeof(hip_bfloat16),
                             hipMemcpyDeviceToHost));
    checkHipErrors(hipMemcpy(h_x.data(), x, K * sizeof(hip_bfloat16),
                             hipMemcpyDeviceToHost));

    // 计算 CPU Reference
    gemv_cpu(M, K, alpha, h_A.data(), lda, h_x.data(), h_y_ref.data());
  }

  // 列宽
  const int w_table = 80;

  // 表头
  printf("%s\n", std::string(w_table, '-').c_str());
  printf("M=%d, K=%d, N=1\n", M, K);
  printf("lda=%d\n", lda);
  printf("%s\n", std::string(w_table, '-').c_str());
  printf("%-38s %10s %10s %10s %8s\n", "Kernel Name", "Time (us)", "GFLOPS",
         "BW (GB/s)", "Result");

  for (const auto &k : cases) {
    std::string result_status = "Skipped";

    // 1. Verification (如果启用)
    if (do_verify) {
      // 清零 d_y
      checkHipErrors(hipMemset(y, 0, M * sizeof(hip_bfloat16)));

      // 运行一次
      k.func(M, K, alpha, A, lda, x, y);
      checkHipErrors(hipDeviceSynchronize());

      // 拷回结果
      checkHipErrors(hipMemcpy(h_y_gpu.data(), y, M * sizeof(hip_bfloat16),
                               hipMemcpyDeviceToHost));

      if (verify_result(M, h_y_gpu.data(), h_y_ref.data())) {
        result_status = "PASS";
      } else {
        result_status = "FAIL";
      }
    }

    // 2. Warmup
    for (int i = 0; i < 100; ++i) {
      k.func(M, K, alpha, A, lda, x, y);
    }
    checkHipErrors(hipDeviceSynchronize());

    // 3. Timing
    int num_runs = 1000;
    checkHipErrors(hipEventRecord(start));
    for (int i = 0; i < num_runs; ++i) {
      k.func(M, K, alpha, A, lda, x, y);
    }
    checkHipErrors(hipEventRecord(stop));
    checkHipErrors(hipEventSynchronize(stop));

    float total_ms = 0;
    checkHipErrors(hipEventElapsedTime(&total_ms, start, stop));
    float avg_ms = total_ms / num_runs;

    // 4. Metrics
    double gflops = (2.0 * M * K) / (avg_ms * 1e-3) / 1e9;

    // Bandwidth = Read A + Read x + Write y
    // A: M*K, x: K, y: M
    double bytes_moved = (double)(M * K + K + M) * sizeof(hip_bfloat16);
    double bw = bytes_moved / (avg_ms * 1e-3) / 1e9;

    printf("%-38s %10.1f %10.2f %10.2f %8s\n", k.name.c_str(), avg_ms * 1e3, gflops,
           bw, result_status.c_str());
  }

  std::cout << std::string(w_table, '-') << std::endl;

  checkHipErrors(hipEventDestroy(start));
  checkHipErrors(hipEventDestroy(stop));

  return;
}