Revision history for hhlo

0.1.0.0 -- 2026-04-22

• Initial release.
• Type-safe EDSL for StableHLO with 50+ ops.
• CPU execution via PJRT CPU plugin.
• GPU execution via PJRT CUDA plugin with device enumeration and selection.
• Multi-GPU concurrent inference scaling via executeReplicas.
• 115 CPU tests + 6 GPU integration tests.
• 29 executable examples including ResNet-18, AlexNet, Transformer, and UNet.

0.2.0.0 -- 2026-04-22

BREAKING: Operation AST changed from single-result to multi-result. Any code using opResult / opResultType or pattern-matching on the Operation constructor must update to opResults / opResultTypes.

• Multi-result Operation AST — Operation now supports opResults :: [ValueId] and opResultTypes :: [TensorType], enabling ops with multiple outputs such as stablehlo.rng_bit_generator.
• Multi-value control flow — added whileLoop2, conditional2, whileLoopN, and conditionalN for carrying multiple typed tensors through loops and conditionals without manual packing.
• Random number generation — added rngUniform, rngNormal, and rngBitGenerator to the EDSL, wrapping stablehlo.rng and stablehlo.rng_bit_generator.
• PJRT CPU v1.16.0 parser compatibility fixes:
  • stablehlo.compare now emits generic form with enum attributes (#stablehlo<comparison_direction LT>) instead of custom form.
  • stablehlo.rng and stablehlo.rng_bit_generator emit generic form.
  • func.return for multi-result functions no longer wraps types in parentheses.
• New examples: 30-rng-uniform, 31-rng-normal, 32-rng-bit-generator, 33-multi-value-loop.
• Updated example 12-while from print-only to fully executable.
• Test count: 124 CPU tests + 6 GPU integration tests.

0.3.0.0 -- 2026-04-25

BREAKING: compare and lessThan now return shape-preserving Tensor s 'Bool instead of scalar Tensor '[] 'Bool. New exports sqrt, sin, cos, tan, floor, ceil may conflict with Prelude.

• New primitive ops: sqrt, rsqrt, sin, cos, tan, pow, log1p, floor, ceil.
• New composite / convenience ops: sigmoid, sumAll, pack2, pack3, slice1.
• Fixed compare to return shape-preserving Tensor s 'Bool per StableHLO spec.
• New comparison wrappers: equal, notEqual, greaterThan, lessThanOrEqual, greaterThanOrEqual.
• Test count: 141 CPU tests + 6 GPU integration tests.

0.4.0.0 -- 2026-04-26

BREAKING: HostType 'Bool changed from Bool to Word8 to match PJRT's PRED buffer transfer semantics.

• Convenience layer — two new modules that eliminate boilerplate for the common compile-and-run workflow:
  • HHLO.ModuleBuilder provides buildModule @nIn @nOut, a polymorphic entry point (via TypeApplications) that auto-generates FuncArg declarations and wires up arg calls. No more natVal or FuncArg boilerplate.
  • HHLO.Session provides withCPU, withGPU, withGPUDevice, compile, run, runAsync, and typed HostTensor host-device transfers. No more manual render, toDeviceF32, fromDeviceF32, or shape lists.
• whileLoop3–whileLoop8 and conditional3–conditional8 for carrying 3–8 heterogeneous tensors through control flow.
• Boolean logic ops: logicalAnd, logicalOr, logicalNot.
• New dependency: directory (for plugin-path discovery in withCPU/withGPU).
• Test count: 155 CPU tests + 6 GPU integration tests.

0.5.0.0 -- 2026-04-27

• Autograd — reverse-mode automatic differentiation is now part of HHLO. New module HHLO.Autograd provides grad and vjp combinators that transform HHLO computation graphs into their gradients, producing new StableHLO modules that compile via PJRT. VJP rules cover ~25 ops including element-wise arithmetic, matmul, transpose, reshape, broadcast, reduce, slice, pad, concatenate, select, and more.
• New convenience ops:
  • einsum — Einstein summation via subscript strings (e.g. "ij,jk->ik"). Parses labels, computes batch/contracting dims, and emits the correct stablehlo.dot_general + optional stablehlo.transpose.
  • split — split a tensor into N equal parts along a dimension.
  • stack — stack N tensors along a new axis.
  • productAll, productDim — product reductions (mirrors sumAll/reduceSumDim).
  • topK — return top-K values along a dimension via sort + slice.
• Bug fix: stablehlo.sort now wraps its region in parentheses for PJRT v1.16.0 parser compatibility.
• Test count: 181 CPU tests + 6 GPU integration tests.

0.6.0.0 -- 2026-04-28

• Convolution & pooling VJP rules — autograd now supports backprop through conv2d, transposeConvolution, maxPool, and avgPool.
  • vjpConvolution / vjpTransposeConvolution emit backward input via flipped-kernel transposed conv and skip backward-kernel computation when the kernel is a constant (the common gradModule case).
  • vjpReduceWindow supports both sum-based (avgPool) and select-mask-based (maxPool) backward passes.
  • New primitive emitters: bconvolution, breverse.
  • PJRT parser compatibility: stablehlo.reverse custom pretty-printer and batch_group_count / feature_group_count attributes on backward convs.

0.7.0.0 -- 2026-04-28

• Multi-parameter gradients — gradModule is no longer limited to a single input. New combinators gradModule2, gradModule3, grad2, grad3 differentiate w.r.t. multiple tensors natively.

• ParamTree — generic pack/unpack for structured parameter records. Derive via GHC.Generics and use gradWithParams to train models with dozens of weight tensors without manual offset math.

  data MLPParams = MLPParams { w :: Tensor '[2,2] 'F32, b :: Tensor '[2] 'F32 }
      deriving (Generic)
  instance ParamTree MLPParams
  trainStep params x = gradWithParams loss params x
  

• New E2E autograd tests: grad conv2d, grad maxPool, grad avgPool, grad2 multiply, gradWithParams.

• New unit tests: vjpConvolution, vjpTransposeConvolution, vjpReduceWindow, gradModule2.

• Bug fix: vjpSlice padding value is now a 0D scalar (required by stablehlo.pad).

• Comprehensive tutorial — new document doc/tutorial.md (720 lines) providing a complete guided tour from add two scalars to multi-GPU distributed inference. Covers: shapes-as-types, the full EDSL, NN primitives, autograd (grad/grad2/grad3/ParamTree), control flow, async execution, and a deep-dive into the architecture and PJRT pipeline.

• Test count: 190 CPU tests + 6 GPU integration tests.

0.8.0.0 -- 2026-04-29

• Nested ParamTree — ParamTree now supports arbitrarily nested records via an overlapping GParamTree (K1 R a) instance. Fields can be other ParamTree records, not just bare Tensors.

  data LayerParams = LayerParams { w :: Tensor '[2] 'F32, b :: Tensor '[2] 'F32 }
      deriving (Generic)
  instance ParamTree LayerParams
  
  data ModelParams = ModelParams { layer1 :: LayerParams, layer2 :: LayerParams }
      deriving (Generic)
  instance ParamTree ModelParams
  

• New E2E autograd test: gradWithParams nested.
• Massive GPU test expansion — from 6 to 82 GPU integration tests.
  • New shared GPU test harness (Test.Runtime.GPUResource) using tasty withResource for a single PJRT client shared across all GPU tests.
  • GPU counterparts for nearly all CPU EndToEnd test categories: Arithmetic (15), Shape (8), Matmul (6), NN (7), Reductions (5), DataMovement (15), MultiValue (6), Autograd (10), Session (4).
  • New typed GPU helpers: toDeviceF32On, toDevicePredOn, toDeviceS64On.
  • Total: 191 CPU tests + 82 GPU tests = 273 tests.
• New sessionFrom constructor in HHLO.Session — create a Session from an existing PJRT API/client/device without loading a new plugin.
• Fixed CUDA_ERROR_OUT_OF_MEMORY warnings during GPU tests by converting SessionGPU tests to reuse the shared PJRT client (was creating 4 separate clients via withGPU, each contending for the same GPU memory).
• Moved getPluginPath from HHLO.Session to HHLO.Runtime.PJRT.Plugin. withPJRTCPU and withPJRTGPU now resolve plugin paths via the HHLO_PJRT_CPU_PLUGIN / HHLO_PJRT_GPU_PLUGIN environment variables (falling back to deps/pjrt/), so downstream libraries no longer need to reimplement plugin discovery.

0.9.0.0 -- 2026-04-20

• Fixed-length configuration vectors — rank-polymorphic EDSL ops now use vector-sized to tie config vector lengths to tensor ranks at compile time. This eliminates the class of bugs where wrong-length config silently produces invalid StableHLO.
  • Phase 1 (2D NN primitives): conv2dWithPadding, maxPool, avgPool, transposeConvolution accept V2 Int64 / P2.
  • Phase 2+ (rank-polymorphic ops): transpose, slice, pad, dynamicSlice, reduceWindow, and dotGeneral now accept Vector (Length s) Int64 or separate Vector n Int64 type parameters instead of raw [Int64].

  -- BEFORE (could silently miscompile)
  transpose [1, 0] x
  slice x [1] [3] [1]
  dotGeneral [] [] [1] [0] x y
  
  -- AFTER (type-safe)
  transpose (v2 1 0) x
  slice x (v1 1) (v1 3) (v1 1)
  dotGeneral VS.empty VS.empty (v1 1) (v1 0) x y
  

  New exports in HHLO.Core.Types: Length type family, V, V1, V2, V3, V4, Padding, P2, plus smart constructors v1, v2, v3, v4, p2.
• New dependency: vector-sized >= 1.5 && < 1.6.
• Fix transposeConvolution lhs_dilation bug — passing a 2-element spatial dilation list no longer drops the second element.
• gather and scatter kept as [Int64] for now. Their config vector lengths depend on complex relationships between operand / indices / result ranks, so a clean type-safe design requires a separate future phase.