warp.tile\_slice\_indexed
=========================

.. function:: warp._src.lang.tile_slice_indexed(t: Tile[Any, tuple[int, ...]], indices: tuple) -> Tile[Any, tuple[int, ...]]

   .. wp-builtin-tags::
      :kernel: true
      :python: false
      :differentiable: true

   Gather elements of a tile along a single axis using a 1D tile of integer indices.
   
   This implements the advanced-indexing syntax ``t[indices, :]``.
   
   The current implementation places the source and index tiles in shared memory, where
   they count against the block's shared-memory budget (see
   :ref:`tile_shared_memory_budget`).
   
   Unlike :func:`~warp.tile_view`, the result is a copy, so writing to it leaves ``t``
   unchanged. Negative indices count from the end of the indexed axis
   (``-1`` selects the last element); indices beyond either end are invalid. Indices may
   repeat; duplicate indices accumulate their gradients atomically in the backward pass.
   
   :param t: Input tile to gather from
   :param indices: Advanced-indexing subscript tuple. Exactly one entry must be a non-empty
                   1D integer index tile; every other entry must be a full ``:`` slice. Trailing
                   axes may be omitted.
   
   :returns: A tile with the shape of ``t``, except along the gathered axis where the extent
             equals the number of indices.
   
   .. rubric:: Example
   
   .. testcode::
   
       @wp.kernel
       def gather_rows(a: wp.array2d[float], indices: wp.array[int], out: wp.array2d[float]):
           t = wp.tile_load(a, shape=(4, 4))
           i = wp.tile_load(indices, shape=3)
   
           wp.tile_store(out, t[i, :])
   
       a = wp.array(np.arange(1, 17, dtype=np.float32).reshape(4, 4), dtype=float)
       indices = wp.array([3, 0, -1], dtype=int)
       out = wp.zeros((3, 4), dtype=float)
   
       wp.launch_tiled(gather_rows, dim=1, inputs=[a, indices], outputs=[out], block_dim=8)
   
       print(out.numpy())
   
   .. testoutput::
   
       [[13. 14. 15. 16.]
        [ 1.  2.  3.  4.]
        [13. 14. 15. 16.]]