从双指针构造 Arrow DoubleArray

Question

我有一个二维双精度数组指针。我可以将它转换为 u_int8_t，将其提取到 Arrow Pool Buffer 的 mutable_data()，然后构造一个 Arrow DoubleArray。但是，当我从数组的 Value()、raw_values() 中获取值时，我无法获取正确的数字。有人请看我的代码并帮助我：

double* generateDoubleArray() {
    int totalColumns = 200;
    int totalRows = 200;
    std::random_device r;
    std::default_random_engine e1(r());
    std::normal_distribution<double> nor_dist(-1, 1);

    double *A = static_cast<double *>(malloc(totalColumns * totalRows * sizeof(double *)));
    for (int i = 0; i < totalRows; i++) {
        for (int j = 0; j < totalColumns; j++) {
            A[i*totalColumns + j] = sin(nor_dist(e1)) + exp(sin(nor_dist(e1)) + cos(nor_dist(e1)));
        }
    }

    return A;
}
int main()
{
    double* generatedDouble = generateDoubleArray();
    uint8_t *ui_generatedDouble = (uint8_t*)generatedDouble;
    arrow::MemoryPool* pool_;
    pool_ = arrow::default_memory_pool();
    auto data = std::make_shared<arrow::PoolBuffer>(pool_);
    size_t length = 200 * 200;
    const size_t data_nbytes = length * sizeof(double *);

    data->Resize(data_nbytes);
    *data->mutable_data() = *ui_generatedDouble;
    auto out = std::make_shared<arrow::DoubleArray>(data_nbytes, data);

    double test_value = out->Value(0); // The returned value is not correct

    return 0;
}

谢谢

Answer 1

下面这行和你想的不一样：

*data->mutable_data() = *ui_generatedDouble;

它只复制数据的第一个字节。你想 memcopy 整个缓冲区：

std::memcpy(data->mutable_data(), ui_generatedDouble, data_nbytes);

从双指针构造 Arrow DoubleArray

Construct an Arrow DoubleArray from double pointer

c++

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