add support for f16 (#888)

arrow/Cargo.toml

@@ -43,6 +43,7 @@ serde_json = { version = "1.0", features = ["preserve_order"] }
 indexmap = "1.6"
 rand = { version = "0.8", optional = true }
 num = "0.4"
+half = "1.8"
 csv_crate = { version = "1.1", optional = true, package="csv" }
 regex = "1.3"
 lazy_static = "1.4"

arrow/src/alloc/types.rs

@@ -16,6 +16,7 @@
 // under the License.
 
 use crate::datatypes::DataType;
+use half::f16;
 
 /// A type that Rust's custom allocator knows how to allocate and deallocate.
 /// This is implemented for all Arrow's physical types whose in-memory representation
@@ -67,5 +68,6 @@ create_native!(
     i64,
     DataType::Int64 | DataType::Date64 | DataType::Time64(_) | DataType::Timestamp(_, _)
 );
+create_native!(f16, DataType::Float16);
 create_native!(f32, DataType::Float32);
 create_native!(f64, DataType::Float64);

arrow/src/array/array.rs

@@ -240,7 +240,7 @@ pub fn make_array(data: ArrayData) -> ArrayRef {
         DataType::UInt16 => Arc::new(UInt16Array::from(data)) as ArrayRef,
         DataType::UInt32 => Arc::new(UInt32Array::from(data)) as ArrayRef,
         DataType::UInt64 => Arc::new(UInt64Array::from(data)) as ArrayRef,
-        DataType::Float16 => panic!("Float16 datatype not supported"),
+        DataType::Float16 => Arc::new(Float16Array::from(data)) as ArrayRef,
         DataType::Float32 => Arc::new(Float32Array::from(data)) as ArrayRef,
         DataType::Float64 => Arc::new(Float64Array::from(data)) as ArrayRef,
         DataType::Date32 => Arc::new(Date32Array::from(data)) as ArrayRef,
@@ -393,7 +393,7 @@ pub fn new_null_array(data_type: &DataType, length: usize) -> ArrayRef {
         DataType::UInt8 => new_null_sized_array::<UInt8Type>(data_type, length),
         DataType::Int16 => new_null_sized_array::<Int16Type>(data_type, length),
         DataType::UInt16 => new_null_sized_array::<UInt16Type>(data_type, length),
-        DataType::Float16 => unreachable!(),
+        DataType::Float16 => new_null_sized_array::<Float16Type>(data_type, length),
         DataType::Int32 => new_null_sized_array::<Int32Type>(data_type, length),
         DataType::UInt32 => new_null_sized_array::<UInt32Type>(data_type, length),
         DataType::Float32 => new_null_sized_array::<Float32Type>(data_type, length),

arrow/src/array/data.rs

@@ -18,17 +18,17 @@
 //! Contains `ArrayData`, a generic representation of Arrow array data which encapsulates
 //! common attributes and operations for Arrow array.
 
-use std::convert::TryInto;
-use std::mem;
-use std::sync::Arc;
-
 use crate::datatypes::{DataType, IntervalUnit};
 use crate::error::{ArrowError, Result};
 use crate::{bitmap::Bitmap, datatypes::ArrowNativeType};
 use crate::{
     buffer::{Buffer, MutableBuffer},
     util::bit_util,
 };
+use half::f16;
+use std::convert::TryInto;
+use std::mem;
+use std::sync::Arc;
 
 use super::equal::equal;
 
@@ -89,6 +89,10 @@ pub(crate) fn new_buffers(data_type: &DataType, capacity: usize) -> [MutableBuff
             MutableBuffer::new(capacity * mem::size_of::<i64>()),
             empty_buffer,
         ],
+        DataType::Float16 => [
+            MutableBuffer::new(capacity * mem::size_of::<f16>()),
+            empty_buffer,
+        ],
         DataType::Float32 => [
             MutableBuffer::new(capacity * mem::size_of::<f32>()),
             empty_buffer,
@@ -178,7 +182,6 @@ pub(crate) fn new_buffers(data_type: &DataType, capacity: usize) -> [MutableBuff
             ],
             _ => unreachable!(),
         },
-        DataType::Float16 => unreachable!(),
         DataType::FixedSizeList(_, _) | DataType::Struct(_) => {
             [empty_buffer, MutableBuffer::new(0)]
         }
@@ -319,7 +322,7 @@ impl ArrayData {
         buffers: Vec<Buffer>,
         child_data: Vec<ArrayData>,
     ) -> Result<Self> {
-        // Safetly justification: `validate` is (will be) called below
+        // Safety justification: `validate` is (will be) called below
         let new_self = unsafe {
             Self::new_unchecked(
                 data_type,
@@ -519,6 +522,7 @@ impl ArrayData {
             | DataType::Int16
             | DataType::Int32
             | DataType::Int64
+            | DataType::Float16
             | DataType::Float32
             | DataType::Float64
             | DataType::Date32
@@ -554,7 +558,6 @@ impl ArrayData {
             DataType::Dictionary(_, data_type) => {
                 vec![Self::new_empty(data_type)]
             }
-            DataType::Float16 => unreachable!(),
         };
 
         // Data was constructed correctly above

arrow/src/array/equal/mod.rs

@@ -25,11 +25,11 @@ use super::{
     GenericStringArray, MapArray, NullArray, OffsetSizeTrait, PrimitiveArray,
     StringOffsetSizeTrait, StructArray,
 };
-
 use crate::{
     buffer::Buffer,
     datatypes::{ArrowPrimitiveType, DataType, IntervalUnit},
 };
+use half::f16;
 
 mod boolean;
 mod decimal;
@@ -251,7 +251,9 @@ fn equal_values(
             ),
             _ => unreachable!(),
         },
-        DataType::Float16 => unreachable!(),
+        DataType::Float16 => primitive_equal::<f16>(
+            lhs, rhs, lhs_nulls, rhs_nulls, lhs_start, rhs_start, len,
+        ),
         DataType::Map(_, _) => {
             list_equal::<i32>(lhs, rhs, lhs_nulls, rhs_nulls, lhs_start, rhs_start, len)
         }

arrow/src/array/mod.rs

@@ -192,6 +192,14 @@ pub type UInt64Array = PrimitiveArray<UInt64Type>;
 ///
 /// # Example: Using `collect`
 /// ```
+/// # use arrow::array::Float16Array;
+/// use half::f16;
+/// let arr : Float16Array = [Some(f16::from_f64(1.0)), Some(f16::from_f64(2.0))].into_iter().collect();
+/// ```
+pub type Float16Array = PrimitiveArray<Float16Type>;
+///
+/// # Example: Using `collect`
+/// ```
 /// # use arrow::array::Float32Array;
 /// let arr : Float32Array = [Some(1.0), Some(2.0)].into_iter().collect();
 /// ```

arrow/src/array/transform/mod.rs

@@ -15,20 +15,20 @@
 // specific language governing permissions and limitations
 // under the License.
 
+use super::{
+    data::{into_buffers, new_buffers},
+    ArrayData, ArrayDataBuilder,
+};
+use crate::array::StringOffsetSizeTrait;
 use crate::{
     buffer::MutableBuffer,
     datatypes::DataType,
     error::{ArrowError, Result},
     util::bit_util,
 };
+use half::f16;
 use std::mem;
 
-use super::{
-    data::{into_buffers, new_buffers},
-    ArrayData, ArrayDataBuilder,
-};
-use crate::array::StringOffsetSizeTrait;
-
 mod boolean;
 mod fixed_binary;
 mod list;
@@ -266,7 +266,7 @@ fn build_extend(array: &ArrayData) -> Extend {
         DataType::Dictionary(_, _) => unreachable!("should use build_extend_dictionary"),
         DataType::Struct(_) => structure::build_extend(array),
         DataType::FixedSizeBinary(_) => fixed_binary::build_extend(array),
-        DataType::Float16 => unreachable!(),
+        DataType::Float16 => primitive::build_extend::<f16>(array),
         /*
         DataType::FixedSizeList(_, _) => {}
         DataType::Union(_) => {}
@@ -315,7 +315,7 @@ fn build_extend_nulls(data_type: &DataType) -> ExtendNulls {
         },
         DataType::Struct(_) => structure::extend_nulls,
         DataType::FixedSizeBinary(_) => fixed_binary::extend_nulls,
-        DataType::Float16 => unreachable!(),
+        DataType::Float16 => primitive::extend_nulls::<f16>,
         /*
         DataType::FixedSizeList(_, _) => {}
         DataType::Union(_) => {}
@@ -429,6 +429,7 @@ impl<'a> MutableArrayData<'a> {
             | DataType::Int16
             | DataType::Int32
             | DataType::Int64
+            | DataType::Float16
             | DataType::Float32
             | DataType::Float64
             | DataType::Date32
@@ -467,7 +468,6 @@ impl<'a> MutableArrayData<'a> {
             }
             // the dictionary type just appends keys and clones the values.
             DataType::Dictionary(_, _) => vec![],
-            DataType::Float16 => unreachable!(),
             DataType::Struct(fields) => match capacities {
                 Capacities::Struct(capacity, Some(ref child_capacities)) => {
                     array_capacity = capacity;

arrow/src/datatypes/native.rs

@@ -15,9 +15,9 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use serde_json::{Number, Value};
-
 use super::DataType;
+use half::f16;
+use serde_json::{Number, Value};
 
 /// Trait declaring any type that is serializable to JSON. This includes all primitive types (bool, i32, etc.).
 pub trait JsonSerializable: 'static {
@@ -293,6 +293,12 @@ impl ArrowNativeType for u64 {
     }
 }
 
+impl JsonSerializable for f16 {
+    fn into_json_value(self) -> Option<Value> {
+        Number::from_f64(f64::round(f64::from(self) * 1000.0) / 1000.0).map(Value::Number)
+    }
+}
+
 impl JsonSerializable for f32 {
     fn into_json_value(self) -> Option<Value> {
         Number::from_f64(f64::round(self as f64 * 1000.0) / 1000.0).map(Value::Number)
@@ -305,6 +311,7 @@ impl JsonSerializable for f64 {
     }
 }
 
+impl ArrowNativeType for f16 {}
 impl ArrowNativeType for f32 {}
 impl ArrowNativeType for f64 {}
 

arrow/src/datatypes/types.rs

@@ -16,6 +16,7 @@
 // under the License.
 
 use super::{ArrowPrimitiveType, DataType, IntervalUnit, TimeUnit};
+use half::f16;
 
 // BooleanType is special: its bit-width is not the size of the primitive type, and its `index`
 // operation assumes bit-packing.
@@ -46,6 +47,7 @@ make_type!(UInt8Type, u8, DataType::UInt8);
 make_type!(UInt16Type, u16, DataType::UInt16);
 make_type!(UInt32Type, u32, DataType::UInt32);
 make_type!(UInt64Type, u64, DataType::UInt64);
+make_type!(Float16Type, f16, DataType::Float16);
 make_type!(Float32Type, f32, DataType::Float32);
 make_type!(Float64Type, f64, DataType::Float64);
 make_type!(