warp.tile\_stack\_pop
=====================

.. function:: warp._src.lang.tile_stack_pop(s: Any) -> tuple[Any, int]

   .. hlist::
      :columns: 8

      * Kernel

   Pop a value from a tile stack (cooperative).
   
   All threads in the block must call this function. Each calling thread
   races for a slot.
   
   :param s: The tile stack
   
   :returns: A tuple ``(value, slot)`` where ``value`` is the popped element
             (or the default value if the stack was empty) and ``slot`` is the
             index of the popped element (the slot it previously occupied), or
             ``-1`` if the stack was empty. When non-negative, ``slot`` lies in
             ``[0, capacity-1]``. Consistent with :func:`tile_stack_push`
             which also uses ``-1`` to indicate failure.
   
   .. rubric:: Example
   
   .. code-block:: python
   
       CAP = wp.constant(8)
   
       @wp.kernel
       def pop_kernel(out: wp.array[int]):
           _i, j = wp.tid()
           s = wp.tile_stack(capacity=CAP, dtype=int)
           wp.tile_stack_push(s, j * 10, j < 4)
   
           val, slot = wp.tile_stack_pop(s)
           if slot != -1:
               out[slot] = val
   
       out = wp.full(8, -1, dtype=int)
       wp.launch_tiled(pop_kernel, dim=[1], inputs=[out], block_dim=8)
   
       vals = out.numpy()
       print(sorted(vals[vals >= 0].tolist()))
   
   .. code-block:: text
   
       [0, 10, 20, 30]