Function SizeOf

include/singa/core/tensor.h:40–45

                             sizeof(int),    sizeof(char),
                             sizeof(double), sizeof(unsigned char)};
inline size_t SizeOf(DataType t) {
  static_assert(kNumDataType == sizeof(kDataWidth) / sizeof(size_t),
                "Num of data types not match num of data width");
  CHECK_GT(kNumDataType, t);
  return kDataWidth[t];
}

/// A Tensor instance is a multi-dimensional array resident on a Device
/// (default device is the host CPU). The internal data is allocated in lazy