Support iota LAX operation in TessellateIPU (#35)

docs/operations.md

@@ -70,7 +70,7 @@
 | `imag`                 | :x:                | :x:                |         |
 | `index_in_dim`         | :x:                | :x:                |         |
 | `index_take`           | :x:                | :x:                |         |
-| `iota`                 | :x:                | :x:                |         |
+| `iota`                 | :white_check_mark: | n/a                |         |
 | `is_finite`            | :white_check_mark: | :x:                |         |
 | `le`                   | :white_check_mark: | :x:                |         |
 | `lt`                   | :white_check_mark: | :x:                |         |

tessellate_ipu/lax/tile_lax_unary.py

@@ -2,6 +2,7 @@
 import os
 from typing import Any, Dict, List, Tuple
 
+import numpy as np
 from jax import lax
 from jax._src.lax.lax import copy_p
 from jax.core import Primitive, ShapedArray
@@ -13,6 +14,7 @@
     get_ipu_tile_primitive_translation,
     get_ipu_type_name,
     make_ipu_vertex_attributes,
+    make_ipu_vertex_constant_info,
     make_ipu_vertex_in_info,
     make_ipu_vertex_inout_info,
     make_ipu_vertex_name_templated,
@@ -232,6 +234,51 @@ def ipu_integer_pow_translation(
 register_ipu_tile_primitive(lax.integer_pow_p, ipu_integer_pow_translation)
 
 
+def ipu_iota_translation(
+    p: Primitive,
+    tiles: Tuple[int, ...],
+    inavals: List[ShapedArray],
+    attributes: Dict[str, Any] = None,
+) -> IpuTileMapEquation:
+    """IPU `iota` primitive translation rule to IPU vertex.
+
+    Args:
+        p: JAX primitive.
+        tiles: Collection of tiles.
+        inavals: Input shaped arrays.
+        attributes: (unused) attributes.
+    Returns:
+        IPU tile map primitive structure.
+    """
+    assert len(inavals) == 0
+    assert attributes is not None
+    print(attributes)
+    dtype = attributes["dtype"]
+    dimension = int(attributes["dimension"])
+    shape = attributes["shape"]
+
+    assert dimension == 0
+    assert len(shape) == 1
+    # Iota vertex in/outs
+    vname = make_ipu_vertex_name_templated("popops::Iota", dtype)
+    outaval = p.abstract_eval(dtype=dtype, dimension=dimension, shape=shape)[0]
+    inputs_info = [make_ipu_vertex_constant_info("offsets", np.array([0], dtype=dtype))]
+    outputs_info = [make_ipu_vertex_out_info("out", outaval, vertex_dim2=shape[0])]
+    ipu_prim_info = IpuTileMapEquation(
+        vname=vname,
+        pname=p.name,
+        tiles=tiles,
+        inputs_info=inputs_info,
+        outputs_info=outputs_info,
+        attributes_i32=[],
+        attributes_f32=[],
+    )
+    return ipu_prim_info
+
+
+register_ipu_tile_primitive(lax.iota_p, ipu_iota_translation)
+
+
 # On tile (mem)copy primitive.
 def ipu_tile_memcpy(
     p: Primitive,

tests/lax/test_tile_lax_basic.py

@@ -192,6 +192,29 @@ def compute_fn(input):
         assert output_ipu.shape == inshape
         npt.assert_array_almost_equal(output_ipu, output_cpu, decimal=2)
 
+    @parameterized.parameters(
+        [
+            (np.int32,),
+        ]
+    )
+    def test__tile_map__iota__ipu_jitting__proper_result(self, dtype):
+        tiles = (3, 4, 5)
+        N = 64
+
+        def compute_fn():
+            return tile_map(lax.iota_p, dtype=dtype, dimension=0, shape=(N,), tiles=tiles)
+
+        # compute_fn_cpu = partial(jax.jit, backend="cpu")(compute_fn)
+        compute_fn_ipu = partial(jax.jit, backend="ipu")(compute_fn)
+
+        output_ipu = compute_fn_ipu()
+        expected_output = np.stack([np.arange(0, N, dtype=dtype)] * len(tiles))
+        assert isinstance(output_ipu, TileShardedArray)
+        assert output_ipu.tiles == tiles
+        assert output_ipu.dtype == dtype
+        assert output_ipu.shape == (len(tiles), N)
+        npt.assert_array_equal(output_ipu, expected_output)
+
 
 @pytest.mark.ipu_hardware
 class IpuTileUnaryPrimitiveHwTests(chex.TestCase):