Add support for Float16

.github/workflows/CI.yml

@@ -47,7 +47,7 @@ jobs:
   #     - uses: julia-actions/julia-runtest@v1
 
   HDF5:
-    name: julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }}
+    name: julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ matrix.hdf5_jll }}
     runs-on: ${{ matrix.os }}
     timeout-minutes: 20
     strategy:
@@ -57,27 +57,31 @@ jobs:
           # We need to keep the association between OS and ARCH, and
           # there is no good way to express this as a matrix. Hence we
           # duplicate for all Julia versions.
-          - {version: '1.10', os: ubuntu-24.04, arch: x64}
-          - {version: '1.10', os: ubuntu-24.04, arch: x86}
-          - {version: '1.10', os: ubuntu-24.04-arm, arch: aarch64}
-          - {version: '1.10', os: macOS-15-intel, arch: x64}
-          - {version: '1.10', os: macOS-26, arch: aarch64}
-          - {version: '1.10', os: windows-2025, arch: x64}
-          - {version: '1.10', os: windows-2025, arch: x86}
-          - {version: '1', os: ubuntu-24.04, arch: x64}
-          - {version: '1', os: ubuntu-24.04, arch: x86}
-          - {version: '1', os: ubuntu-24.04-arm, arch: aarch64}
-          - {version: '1', os: macOS-15-intel, arch: x64}
-          - {version: '1', os: macOS-26, arch: aarch64}
-          - {version: '1', os: windows-2025, arch: x64}
-          - {version: '1', os: windows-2025, arch: x86}
-          - {version: 'nightly', os: ubuntu-24.04, arch: x64}
-          - {version: 'nightly', os: ubuntu-24.04, arch: x86}
-          - {version: 'nightly', os: ubuntu-24.04-arm, arch: aarch64}
-          - {version: 'nightly', os: macOS-15-intel, arch: x64}
-          - {version: 'nightly', os: macOS-26, arch: aarch64}
-          - {version: 'nightly', os: windows-2025, arch: x64}
-          - {version: 'nightly', os: windows-2025, arch: x86}
+          # Keep coverage for Julia 1.10 with HDF5_jll 1.12
+          # The known-bad combination is Julia 1.12 or later with HDF5_jll 1.12
+          - {version: '1.10', os: ubuntu-24.04, arch: x64, hdf5_jll: '1.12'}
+          - {version: '1.10', os: ubuntu-24.04, arch: x64, hdf5_jll: 'latest'}
+          - {version: '1.10', os: ubuntu-24.04, arch: x86, hdf5_jll: 'latest'}
+          - {version: '1.10', os: ubuntu-24.04-arm, arch: aarch64, hdf5_jll: 'latest'}
+          - {version: '1.10', os: macOS-15-intel, arch: x64, hdf5_jll: 'latest'}
+          - {version: '1.10', os: macOS-26, arch: aarch64, hdf5_jll: 'latest'}
+          - {version: '1.10', os: windows-2025, arch: x64, hdf5_jll: 'latest'}
+          - {version: '1.10', os: windows-2025, arch: x86, hdf5_jll: 'latest'}
+          - {version: '1', os: ubuntu-24.04, arch: x64, hdf5_jll: '1.14'}
+          - {version: '1', os: ubuntu-24.04, arch: x64, hdf5_jll: 'latest'}
+          - {version: '1', os: ubuntu-24.04, arch: x86, hdf5_jll: 'latest'}
+          - {version: '1', os: ubuntu-24.04-arm, arch: aarch64, hdf5_jll: 'latest'}
+          - {version: '1', os: macOS-15-intel, arch: x64, hdf5_jll: 'latest'}
+          - {version: '1', os: macOS-26, arch: aarch64, hdf5_jll: 'latest'}
+          - {version: '1', os: windows-2025, arch: x64, hdf5_jll: 'latest'}
+          - {version: '1', os: windows-2025, arch: x86, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: ubuntu-24.04, arch: x64, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: ubuntu-24.04, arch: x86, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: ubuntu-24.04-arm, arch: aarch64, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: macOS-15-intel, arch: x64, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: macOS-26, arch: aarch64, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: windows-2025, arch: x64, hdf5_jll: 'latest'}
+          - {version: 'nightly', os: windows-2025, arch: x86, hdf5_jll: 'latest'}
     steps:
       - uses: actions/checkout@v6
       - uses: julia-actions/cache@v3
@@ -86,6 +90,14 @@ jobs:
           version: ${{ matrix.version }}
           arch: ${{ matrix.arch }}
       - uses: julia-actions/julia-buildpkg@v1
+      - name: Pin HDF5_jll to ${{ matrix.hdf5_jll }}
+        if: ${{ matrix.hdf5_jll != 'latest' }}
+        shell: julia --project=@. {0}
+        run: |
+          using Pkg
+          Pkg.pin(PackageSpec(name="HDF5_jll", version="${{ matrix.hdf5_jll }}"))
+          Pkg.instantiate()  # ensures Manifest/artifacts match the pin
+
       - uses: julia-actions/julia-runtest@v1
         env:
           JULIA_DEBUG: Main

src/api/types.jl

@@ -523,17 +523,18 @@ const H5T_C_S1            = _read_const(:H5T_C_S1_g)
 const H5T_STD_REF_OBJ     = _read_const(:H5T_STD_REF_OBJ_g)
 const H5T_STD_REF_DSETREG = _read_const(:H5T_STD_REF_DSETREG_g)
 # Native types
-const H5T_NATIVE_B8     = _read_const(:H5T_NATIVE_B8_g)
-const H5T_NATIVE_INT8   = _read_const(:H5T_NATIVE_INT8_g)
-const H5T_NATIVE_UINT8  = _read_const(:H5T_NATIVE_UINT8_g)
-const H5T_NATIVE_INT16  = _read_const(:H5T_NATIVE_INT16_g)
-const H5T_NATIVE_UINT16 = _read_const(:H5T_NATIVE_UINT16_g)
-const H5T_NATIVE_INT32  = _read_const(:H5T_NATIVE_INT32_g)
-const H5T_NATIVE_UINT32 = _read_const(:H5T_NATIVE_UINT32_g)
-const H5T_NATIVE_INT64  = _read_const(:H5T_NATIVE_INT64_g)
-const H5T_NATIVE_UINT64 = _read_const(:H5T_NATIVE_UINT64_g)
-const H5T_NATIVE_FLOAT  = _read_const(:H5T_NATIVE_FLOAT_g)
-const H5T_NATIVE_DOUBLE = _read_const(:H5T_NATIVE_DOUBLE_g)
+const H5T_NATIVE_B8      = _read_const(:H5T_NATIVE_B8_g)
+const H5T_NATIVE_INT8    = _read_const(:H5T_NATIVE_INT8_g)
+const H5T_NATIVE_UINT8   = _read_const(:H5T_NATIVE_UINT8_g)
+const H5T_NATIVE_INT16   = _read_const(:H5T_NATIVE_INT16_g)
+const H5T_NATIVE_UINT16  = _read_const(:H5T_NATIVE_UINT16_g)
+const H5T_NATIVE_INT32   = _read_const(:H5T_NATIVE_INT32_g)
+const H5T_NATIVE_UINT32  = _read_const(:H5T_NATIVE_UINT32_g)
+const H5T_NATIVE_INT64   = _read_const(:H5T_NATIVE_INT64_g)
+const H5T_NATIVE_UINT64  = _read_const(:H5T_NATIVE_UINT64_g)
+const H5T_NATIVE_FLOAT16 = _has_symbol(:H5T_NATIVE_FLOAT16_g) ? _read_const(:H5T_NATIVE_FLOAT16_g) : hid_t(-1)
+const H5T_NATIVE_FLOAT   = _read_const(:H5T_NATIVE_FLOAT_g)
+const H5T_NATIVE_DOUBLE  = _read_const(:H5T_NATIVE_DOUBLE_g)
 # Other type constants
 const H5T_VARIABLE = reinterpret(UInt, -1)
 

src/typeconversions.jl

@@ -142,6 +142,13 @@ hdf5_type_id(::Type{Int32})     = API.H5T_NATIVE_INT32
 hdf5_type_id(::Type{UInt32})    = API.H5T_NATIVE_UINT32
 hdf5_type_id(::Type{Int64})     = API.H5T_NATIVE_INT64
 hdf5_type_id(::Type{UInt64})    = API.H5T_NATIVE_UINT64
+function hdf5_type_id(::Type{Float16})
+    if hdf5_supports_Float16
+        return API.H5T_NATIVE_FLOAT16
+    else
+        throw(ArgumentError("Float16 HDF5 datatypes are not supported by the linked HDF5 library"))
+    end
+end
 hdf5_type_id(::Type{Float32})   = API.H5T_NATIVE_FLOAT
 hdf5_type_id(::Type{Float64})   = API.H5T_NATIVE_DOUBLE
 hdf5_type_id(::Type{Reference}) = API.H5T_STD_REF_OBJ
@@ -177,7 +184,9 @@ function _hdf5_type_map(class_id, is_signed, native_size)
             end
         end
     else
-        return if native_size == 4
+        return if native_size == 2
+            Float16
+        elseif native_size == 4
             Float32
         elseif native_size == 8
             Float64

src/types.jl

@@ -151,8 +151,20 @@ Base.cconvert(
     ::Type{Ptr{T}}, ref::Reference
 ) where {T<:Union{Reference,API.hobj_ref_t,Cvoid}} = Ref(ref)
 
+const hdf5_supports_Float16 = API.H5T_NATIVE_FLOAT16 != API.hid_t(-1)
 const BitsType = Union{
-    Bool,Int8,UInt8,Int16,UInt16,Int32,UInt32,Int64,UInt64,Float32,Float64
+    Bool,
+    Int8,
+    UInt8,
+    Int16,
+    UInt16,
+    Int32,
+    UInt32,
+    Int64,
+    UInt64,
+    Float32,
+    Float64,
+    (hdf5_supports_Float16 ? Float16 : Union{})
 }
 const ScalarType = Union{BitsType,Reference}
 

test/plain.jl

@@ -3,6 +3,8 @@ using CRC32c
 using H5Zblosc
 using Test
 
+const test_Float16 = HDF5.hdf5_supports_Float16
+
 gatherf(dst_buf, dst_buf_bytes_used, op_data) = HDF5.API.herr_t(0)
 gatherf_bad(dst_buf, dst_buf_bytes_used, op_data) = HDF5.API.herr_t(-1)
 gatherf_data(dst_buf, dst_buf_bytes_used, op_data) = HDF5.API.herr_t((op_data == 9) - 1)
@@ -41,6 +43,9 @@ end
     A = randn(3, 5)
     write(f, "Afloat64", convert(Matrix{Float64}, A))
     write(f, "Afloat32", convert(Matrix{Float32}, A))
+    if test_Float16
+        write(f, "Afloat16", convert(Matrix{Float16}, A))
+    end
     Ai = rand(1:20, 2, 4)
     write(f, "Aint8", convert(Matrix{Int8}, Ai))
     f["Aint16"] = convert(Matrix{Int16}, Ai)
@@ -176,6 +181,11 @@ end
     @test zerodim == 42 && isa(zerodim, Int32)
     bloscempty = read(fr, "bloscempty")
     @test bloscempty == Int64[] && isa(bloscempty, Vector{Int64})
+    if test_Float16
+        Af16 = read(fr, "Afloat16")
+        @test convert(Matrix{Float16}, A) == Af16
+        @test eltype(Af16) == Float16
+    end
     Af32 = read(fr, "Afloat32")
     @test convert(Matrix{Float32}, A) == Af32
     @test eltype(Af32) == Float32
@@ -611,6 +621,9 @@ end # testset plain
     Acmplx = rand(ComplexF64, 3, 5)
     write(f, "Acmplx64", convert(Matrix{ComplexF64}, Acmplx))
     write(f, "Acmplx32", convert(Matrix{ComplexF32}, Acmplx))
+    if test_Float16
+        write(f, "Acmplx16", convert(Matrix{ComplexF16}, Acmplx))
+    end
 
     dset = create_dataset(
         f, "Acmplx64_hyperslab", datatype(Complex{Float64}), dataspace(Acmplx)
@@ -623,6 +636,11 @@ end # testset plain
     @test_throws ErrorException f["_ComplexF64"] = 1.0 + 2.0im
     @test_throws ErrorException write(f, "_Acmplx64", convert(Matrix{ComplexF64}, Acmplx))
     @test_throws ErrorException write(f, "_Acmplx32", convert(Matrix{ComplexF32}, Acmplx))
+    if test_Float16
+        @test_throws ErrorException write(
+            f, "_Acmplx16", convert(Matrix{ComplexF16}, Acmplx)
+        )
+    end
     HDF5.enable_complex_support()
 
     close(f)
@@ -633,6 +651,11 @@ end # testset plain
     z_attrs = attributes(fr["ComplexF64"])
     @test read(z_attrs["ComplexInt64"]) == 1im
 
+    if test_Float16
+        Acmplx16 = read(fr, "Acmplx16")
+        @test convert(Matrix{ComplexF16}, Acmplx) == Acmplx16
+        @test eltype(Acmplx16) == ComplexF16
+    end
     Acmplx32 = read(fr, "Acmplx32")
     @test convert(Matrix{ComplexF32}, Acmplx) == Acmplx32
     @test eltype(Acmplx32) == ComplexF32
@@ -651,6 +674,10 @@ end # testset plain
     z = read(fr, "ComplexF64")
     @test isa(z, NamedTuple{(:r, :i),Tuple{Float64,Float64}})
 
+    if test_Float16
+        Acmplx16 = read(fr, "Acmplx16")
+        @test eltype(Acmplx16) == NamedTuple{(:r, :i),Tuple{Float16,Float16}}
+    end
     Acmplx32 = read(fr, "Acmplx32")
     @test eltype(Acmplx32) == NamedTuple{(:r, :i),Tuple{Float32,Float32}}
     Acmplx64 = read(fr, "Acmplx64")