# `Edifice.SSM.MambaHillisSteele`
[🔗](https://github.com/blasphemetheus/edifice/blob/main/lib/edifice/ssm/mamba_hillis_steele.ex#L1)

Mamba variant using Hillis-Steele parallel scan.

## Hillis-Steele vs Blelloch

**Blelloch** (standard Mamba): O(L) work, O(log L) depth
- Work-efficient: only half the elements active at each level
- Fewer total operations

**Hillis-Steele**: O(L log L) work, O(log L) depth
- ALL elements active at every level
- More parallelism per level = better GPU occupancy
- May be faster despite more total work

## Algorithm

```
Level 0: [1] [2] [3] [4] [5] [6] [7] [8]
Level 1: [1] [1+2] [2+3] [3+4] [4+5] [5+6] [6+7] [7+8]  (stride 1, ALL elements)
Level 2: [1] [1+2] [1-3] [1-4] [2-5] [3-6] [4-7] [5-8]  (stride 2, ALL elements)
Level 3: [1] [1+2] [1-3] [1-4] [1-5] [1-6] [1-7] [1-8]  (stride 4, ALL elements)
```

## Usage

    model = MambaHillisSteele.build(embed_dim: 287, hidden_size: 256)

# `build_opt`

```elixir
@type build_opt() ::
  {:embed_dim, pos_integer()}
  | {:hidden_size, pos_integer()}
  | {:state_size, pos_integer()}
  | {:expand_factor, pos_integer()}
  | {:conv_size, pos_integer()}
  | {:num_layers, pos_integer()}
  | {:dropout, float()}
  | {:window_size, pos_integer()}
```

Options for `build/1`.

# `build`

```elixir
@spec build([build_opt()]) :: Axon.t()
```

Build a MambaHillisSteele model for sequence processing.

Same API as `Mamba.build/1`.

# `output_size`

```elixir
@spec output_size(keyword()) :: non_neg_integer()
```

# `param_count`

```elixir
@spec param_count(keyword()) :: non_neg_integer()
```

# `recommended_defaults`

```elixir
@spec recommended_defaults() :: keyword()
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*