c-api-demo.c

 
#include <assert.h>
#include <stddef.h>
#include <stdint.h> /* uint32_t,uint64_t */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <xgboost/c_api.h>
 
#define safe_xgboost(call) { \
int err = (call); \
if (err != 0) { \
 fprintf(stderr, "%s:%d: error in %s: %s\n", __FILE__, __LINE__, #call, XGBGetLastError()); \
exit(1); \
}                                                                       \
}
 
/* 创建 Json 编码的数组接口。 */
static void MakeArrayInterface(size_t data, size_t n, char const* typestr, size_t length,
                               char* out) {
  static char const kTemplate[] =
      "{\"data\": [%lu, true], \"shape\": [%lu, %lu], \"typestr\": \"%s\", \"version\": 3}";
memset(out, '\0', length);
sprintf(out, kTemplate, data, n, 1ul, typestr);
}
/* 创建 Json 编码的 DMatrix 配置。 */
static void MakeConfig(int n_threads, size_t length, char* out) {
  static char const kTemplate[] = "{\"missing\": NaN, \"nthread\": %d}";
memset(out, '\0', length);
sprintf(out, kTemplate, n_threads);
}
 
int main() {
  int silent = 0;
  int use_gpu = 0; // 设置为 1 以使用 GPU 进行训练
 
  // 加载数据
  DMatrixHandle dtrain, dtest;
safe_xgboost(XGDMatrixCreateFromFile("../../data/agaricus.txt.train?format=libsvm", silent, &dtrain));
safe_xgboost(XGDMatrixCreateFromFile("../../data/agaricus.txt.test?format=libsvm", silent, &dtest));
 
  // 创建助推器
  BoosterHandle booster;
  DMatrixHandle eval_dmats[2] = {dtrain, dtest};
safe_xgboost(XGBoosterCreate(eval_dmats, 2, &booster));
 
  // 配置训练
  // 可用参数描述于此
  // https://docs.xgboost.com.cn/en/stable/parameter.html
safe_xgboost(XGBoosterSetParam(booster, "device", use_gpu ? "cuda" : "cpu"));
 
safe_xgboost(XGBoosterSetParam(booster, "objective", "binary:logistic"));
safe_xgboost(XGBoosterSetParam(booster, "min_child_weight", "1"));
safe_xgboost(XGBoosterSetParam(booster, "gamma", "0.1"));
safe_xgboost(XGBoosterSetParam(booster, "max_depth", "3"));
safe_xgboost(XGBoosterSetParam(booster, "verbosity", silent ? "0" : "1"));
 
  // 训练并评估 10 次迭代
  int n_trees = 10;
  const char* eval_names[2] = {"train", "test"};
  const char* eval_result = NULL;
  for (int i = 0; i < n_trees; ++i) {
safe_xgboost(XGBoosterUpdateOneIter(booster, i, dtrain));
safe_xgboost(XGBoosterEvalOneIter(booster, i, eval_dmats, eval_names, 2, &eval_result));
printf("%s\n", eval_result);
  }
 
  bst_ulong num_feature = 0;
safe_xgboost(XGBoosterGetNumFeature(booster, &num_feature));
printf("num_feature: %lu\n", (unsigned long)(num_feature));
 
  // 预测
  bst_ulong out_len = 0;
  int n_print = 10;
 
  /* 使用 DMatrix 对象运行预测。 */
  char const config[] =
      "{\"training\": false, \"type\": 0, "
      "\"iteration_begin\": 0, \"iteration_end\": 0, \"strict_shape\": false}";
  /* 输出预测的形状 */
uint64_t const* out_shape;
  /* 输出预测的维度 */
uint64_t out_dim;
  /* 指向线程局部连续数组的指针，在预测函数中赋值。 */
  float const* out_result = NULL;
safe_xgboost(
      XGBoosterPredictFromDMatrix(booster, dtest, config, &out_shape, &out_dim, &out_result));
 
printf("y_pred: ");
  for (int i = 0; i < n_print; ++i) {
printf("%1.4f ", out_result[i]);
  }
printf("\n");
 
  // 打印真实标签
safe_xgboost(XGDMatrixGetFloatInfo(dtest, "label", &out_len, &out_result));
printf("y_test: ");
  for (int i = 0; i < n_print; ++i) {
printf("%1.4f ", out_result[i]);
  }
printf("\n");
 
  {
printf("密集矩阵示例 (XGDMatrixCreateFromMat): ");
 
    const float values[] = {0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0,
      1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0,
      0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0,
      1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      1, 0, 0, 0, 0, 1, 0, 0, 0, 0};
 
    DMatrixHandle dmat;
safe_xgboost(XGDMatrixCreateFromMat(values, 1, 127, 0.0, &dmat));
 
    const float* out_result = NULL;
 
safe_xgboost(
        XGBoosterPredictFromDMatrix(booster, dmat, config, &out_shape, &out_dim, &out_result));
assert(out_dim == 1);
assert(out_shape[0] == 1);
 
printf("%1.4f \n", out_result[0]);
safe_xgboost(XGDMatrixFree(dmat));
  }
 
  {
printf("稀疏矩阵示例 (XGDMatrixCreateFromCSR): ");
 
    const uint64_t indptr[] = {0, 22};
    const uint32_t indices[] = {1, 9, 19, 21, 24, 34, 36, 39, 42, 53, 56,
                                65, 69, 77, 86, 88, 92, 95, 102, 106, 117, 122};
    const float data[] = {1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0,
                          1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0};
 
    DMatrixHandle dmat;
    char j_indptr[128];
MakeArrayInterface((size_t)indptr, 2ul, "<u8", sizeof(j_indptr), j_indptr);
    char j_indices[128];
MakeArrayInterface((size_t)indices, sizeof(indices) / sizeof(uint32_t), "<u4",
                       sizeof(j_indices), j_indices);
    char j_data[128];
MakeArrayInterface((size_t)data, sizeof(data) / sizeof(float), "<f4", sizeof(j_data), j_data);
 
    char j_config[64];
MakeConfig(0, sizeof(j_config), j_config);
 
safe_xgboost(XGDMatrixCreateFromCSR(j_indptr, j_indices, j_data, 127, j_config, &dmat));
 
    const float* out_result = NULL;
 
safe_xgboost(
        XGBoosterPredictFromDMatrix(booster, dmat, config, &out_shape, &out_dim, &out_result));
assert(out_dim == 1);
assert(out_shape[0] == 1);
 
printf("%1.4f \n", out_result[0]);
safe_xgboost(XGDMatrixFree(dmat));
  }
 
  {
printf("稀疏矩阵示例 (XGDMatrixCreateFromCSC): ");
 
    const uint64_t indptr[] = {
        0,  0,  1,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,  2,  2,  2,  3,  3,
        4,  4,  4,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  6,  6,  7,  7,  7,  8,  8,  8,  9,
        9,  9,  9,  9,  9,  9,  9,  9,  9,  9,  10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11,
        12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15,
        15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20,
        20, 20, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22};
 
    const uint32_t indices[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
 
    const float data[] = {1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0,
                          1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0};
 
    char j_indptr[128];
MakeArrayInterface((size_t)indptr, 128ul, "<u8", sizeof(j_indptr), j_indptr);
    char j_indices[128];
MakeArrayInterface((size_t)indices, sizeof(indices) / sizeof(unsigned), "<u4",
                       sizeof(j_indices), j_indices);
    char j_data[128];
MakeArrayInterface((size_t)data, sizeof(data) / sizeof(float), "<f4", sizeof(j_data), j_data);
 
    char j_config[64];
MakeConfig(0, sizeof(j_config), j_config);
 
    DMatrixHandle dmat;
safe_xgboost(XGDMatrixCreateFromCSC(j_indptr, j_indices, j_data, 1, j_config, &dmat));
 
    const float* out_result = NULL;
 
safe_xgboost(
        XGBoosterPredictFromDMatrix(booster, dmat, config, &out_shape, &out_dim, &out_result));
assert(out_dim == 1);
assert(out_shape[0] == 1);
 
printf("%1.4f \n", out_result[0]);
safe_xgboost(XGDMatrixFree(dmat));
  }
 
  // 释放所有资源
safe_xgboost(XGBoosterFree(booster));
safe_xgboost(XGDMatrixFree(dtrain));
safe_xgboost(XGDMatrixFree(dtest));
  return 0;
}