kiszk commented on PR #48215:
URL: https://github.com/apache/arrow/pull/48215#issuecomment-4726381230
@Vishwanatha-HD The existing ReadFloat16Files test reads pre-generated
.parquet files, so it only meaningfully validates the platform those files came
from. Since this is a BE-specific byte-order fix, a write→read round-trip test
that asserts on the actual Float16 bits would guard against regressions on all
platforms.
Would a value-based round-trip like the following example under
`cpp/src/parquet/arrow/arrow_reader_writer_test.cc` make the intent explicit?
```
TEST(TestArrowReaderAdHoc, Float16RoundTripValues) {
using ::arrow::util::Float16;
using ::arrow::HalfFloatArray;
using ::arrow::HalfFloatType;
// Pick values whose two bytes differ, so a missing byte-swap is
detectable.
const std::vector<Float16> values = {
Float16(+1.0), // bits 0x3c00
Float16(-2.0), // bits 0xc000
Float16(+0.5), // bits 0x3800
Float16(-0.0), // bits 0x8000
Float16(65504.0) // bits 0x7bff (max finite)
};
// Build a HalfFloatArray from the raw bits (native endian).
::arrow::HalfFloatBuilder builder;
ASSERT_OK(builder.Append(values[0].bits()));
ASSERT_OK(builder.AppendNull());
for (size_t i = 1; i < values.size(); ++i) {
ASSERT_OK(builder.Append(values[i].bits()));
}
std::shared_ptr<::arrow::Array> array;
ASSERT_OK(builder.Finish(&array));
auto table = ::arrow::Table::Make(
::arrow::schema({::arrow::field("f16", ::arrow::float16())}), {array});
std::shared_ptr<Table> result;
ASSERT_NO_FATAL_FAILURE(
DoSimpleRoundtrip(table, /*use_threads=*/false,
/*row_group_size=*/table->num_rows(), {}, &result));
ASSERT_EQ(result->num_columns(), 1);
ASSERT_EQ(result->column(0)->type()->id(), ::arrow::Type::HALF_FLOAT);
auto chunk =
checked_pointer_cast<HalfFloatArray>(result->column(0)->chunk(0));
ASSERT_TRUE(chunk->IsNull(1));
ASSERT_EQ(chunk->Value(0), values[0].bits());
for (size_t i = 1; i < values.size(); ++i) {
ASSERT_FALSE(chunk->IsNull(static_cast<int64_t>(i) + 1));
ASSERT_EQ(chunk->Value(static_cast<int64_t>(i) + 1), values[i].bits());
}
}
```
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