Test writing and reading a Parquet file with a float16 column

1-write_parquet_float16.cpp

#include <iostream>
#include <arrow/api.h>
#include <arrow/io/api.h>
#include <arrow/util/float16.h>
#include <parquet/arrow/writer.h>

arrow::Status WriteTableToParquetFile() {

  std::shared_ptr<arrow::Array> array;
  arrow::HalfFloatBuilder builder;
  float pi = 3.141592653590;
  float tau = 6.283185307180;
  ARROW_RETURN_NOT_OK(builder.Append(arrow::util::Float16(pi).bits()));
  ARROW_RETURN_NOT_OK(builder.Append(arrow::util::Float16(tau).bits()));
  ARROW_RETURN_NOT_OK(builder.Finish(&array));
  std::vector<std::shared_ptr<arrow::Array>> arrays;
  arrays.push_back(array);

  std::vector<std::shared_ptr<arrow::Field>> schema_vector;
  schema_vector.push_back(arrow::field("x", arrow::float16()));
  auto schema = std::make_shared<arrow::Schema>(schema_vector);

  std::shared_ptr<arrow::Table> table = arrow::Table::Make(schema, arrays);

  std::shared_ptr<arrow::io::FileOutputStream> outfile;
  ARROW_ASSIGN_OR_RAISE(outfile, arrow::io::FileOutputStream::Open("float16.parquet"));

  ARROW_RETURN_NOT_OK(parquet::arrow::WriteTable(*table.get(),
    arrow::default_memory_pool(), outfile));

  return arrow::Status::OK();
}

int main(int, char**) {
  auto status = WriteTableToParquetFile();
  if (!status.ok()) {
    std::cerr << "Error occurred : " << status.message() << std::endl;
    return EXIT_FAILURE;
  }
  return EXIT_SUCCESS;
}

2-read_parquet_float16.cpp

#include <iostream>
#include <arrow/api.h>
#include <arrow/io/api.h>
#include <arrow/util/float16.h>
#include <parquet/arrow/reader.h>

arrow::Status ReadTableFromParquetFile() {

  arrow::MemoryPool* pool = arrow::default_memory_pool();
  std::shared_ptr<arrow::io::RandomAccessFile> input;
  ARROW_ASSIGN_OR_RAISE(input, arrow::io::ReadableFile::Open("float16.parquet"));
  std::unique_ptr<parquet::arrow::FileReader> arrow_reader;
  ARROW_RETURN_NOT_OK(parquet::arrow::OpenFile(input, pool, &arrow_reader));

  std::shared_ptr<arrow::Table> table;
  ARROW_RETURN_NOT_OK(arrow_reader->ReadTable(&table));

  arrow::PrettyPrintOptions options{0};
  ARROW_RETURN_NOT_OK(arrow::PrettyPrint(*table, options, &std::cout));
  
  // Note: The values currently appear as unsigned integers in the printed output.
  // To print them as float16 values, use arrow::util::Float16. For example, to
  // print the first value in the first column:
  std::shared_ptr<arrow::HalfFloatArray> array = 
    std::static_pointer_cast<arrow::HalfFloatArray>(table->column(0)->chunk(0));
  std::cout << std::endl << arrow::util::Float16(array->Value(0)) << std::endl;
  
  return arrow::Status::OK();
}

int main(int, char**) {
  auto status = ReadTableFromParquetFile();
  if (!status.ok()) {
    std::cerr << "Error occurred : " << status.message() << std::endl;
    return EXIT_FAILURE;
  }
  return EXIT_SUCCESS;
}