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| 1 | +.. {#openvino_docs_ops_internal_GatedDeltaNet} |
| 2 | +
|
| 3 | +GatedDeltaNet |
| 4 | +============= |
| 5 | + |
| 6 | + |
| 7 | +.. meta:: |
| 8 | + :description: Learn about GatedDeltaNet - a linear recurrent sequence processing |
| 9 | + operation based on the delta rule with a gating mechanism. |
| 10 | + |
| 11 | +**Versioned name**: *GatedDeltaNet* |
| 12 | + |
| 13 | +**Category**: *Sequence processing* |
| 14 | + |
| 15 | +**Short description**: *GatedDeltaNet* represents a linear recurrent sequence model |
| 16 | +that combines the delta rule memory update with a gating mechanism. |
| 17 | + |
| 18 | +**Detailed description**: *GatedDeltaNet* implements the recurrence from the paper |
| 19 | +`arXiv:2412.06464 <https://arxiv.org/abs/2412.06464>`__. It processes a sequence of |
| 20 | +query, key, and value vectors using the delta rule to update a hidden state matrix, |
| 21 | +controlled by a per-token forget ``gate`` (applied as ``exp(g)``) and a per-token |
| 22 | +write gate ``beta``. Queries are scaled by ``1 / sqrt(key_head_dim)`` before being used |
| 23 | +to compute the output. The following PyTorch-equivalent code illustrates the full |
| 24 | +computation: |
| 25 | + |
| 26 | +.. code-block:: py |
| 27 | +
|
| 28 | + def torch_recurrent_gated_delta_rule( |
| 29 | + query, key, value, recurrent_state, gate, beta, |
| 30 | + ): |
| 31 | + batch_size, sequence_length, num_heads, k_head_dim = key.shape |
| 32 | + v_head_dim = value.shape[-1] |
| 33 | + scale = 1 / (query.shape[-1] ** 0.5) |
| 34 | + query = query * scale |
| 35 | +
|
| 36 | + output_attn = torch.zeros(batch_size, sequence_length, num_heads, v_head_dim).to(value) |
| 37 | + output_recurrent_state = recurrent_state |
| 38 | +
|
| 39 | + for i in range(sequence_length): |
| 40 | + q_t = query[:, i] |
| 41 | + k_t = key[:, i] |
| 42 | + v_t = value[:, i] |
| 43 | + g_t = gate[:, i].exp().unsqueeze(-1).unsqueeze(-1) |
| 44 | + beta_t = beta[:, i].unsqueeze(-1) |
| 45 | +
|
| 46 | + output_recurrent_state = output_recurrent_state * g_t |
| 47 | + kv_mem = (output_recurrent_state * k_t.unsqueeze(-1)).sum(dim=-2) |
| 48 | + delta = (v_t - kv_mem) * beta_t |
| 49 | + output_recurrent_state = output_recurrent_state + k_t.unsqueeze(-1) * delta.unsqueeze(-2) |
| 50 | + output_attn[:, i] = (output_recurrent_state * q_t.unsqueeze(-1)).sum(dim=-2) |
| 51 | +
|
| 52 | + return output_attn, output_recurrent_state |
| 53 | +
|
| 54 | +
|
| 55 | +**Inputs** |
| 56 | + |
| 57 | +* **1**: ``query`` - 4D tensor of type *T* and shape ``[batch_size, seq_len, num_heads, key_head_dim]``, |
| 58 | + the query vectors for each token and head. Scaled internally by ``1 / sqrt(key_head_dim)`` |
| 59 | + before computing the output. **Required.** |
| 60 | + |
| 61 | +* **2**: ``key`` - 4D tensor of type *T* and shape ``[batch_size, seq_len, num_heads, key_head_dim]``, |
| 62 | + the key vectors for each token and head. **Required.** |
| 63 | + |
| 64 | +* **3**: ``value`` - 4D tensor of type *T* and shape ``[batch_size, seq_len, num_heads, value_head_dim]``, |
| 65 | + the value vectors for each token and head. **Required.** |
| 66 | + |
| 67 | +* **4**: ``recurrent_state`` - 4D tensor of type *T* and shape |
| 68 | + ``[batch_size, num_heads, key_head_dim, value_head_dim]``, the recurrent (initially all-zeros) hidden state matrix. **Required.** |
| 69 | + |
| 70 | +* **5**: ``gate`` - 3D tensor of type *T* and shape ``[batch_size, seq_len, num_heads]``, |
| 71 | + the forget gate in log-space. Applied as ``exp(g)`` at each time step to decay the |
| 72 | + hidden state before the delta update. **Required.** |
| 73 | + |
| 74 | +* **6**: ``beta`` - 3D tensor of type *T* and shape ``[batch_size, seq_len, num_heads]``, |
| 75 | + the write gate controlling how much of the delta correction is applied to the hidden |
| 76 | + state. **Required.** |
| 77 | + |
| 78 | + |
| 79 | +**Outputs** |
| 80 | + |
| 81 | +* **1**: ``output_attn`` - 4D tensor of type *T* and shape |
| 82 | + ``[batch_size, seq_len, num_heads, value_head_dim]``, the output vectors at each time step |
| 83 | + produced by applying the state matrix to the (scaled) query. |
| 84 | + |
| 85 | +* **2**: ``output_recurrent_state`` - 4D tensor of type *T* and shape |
| 86 | + ``[batch_size, num_heads, key_head_dim, value_head_dim]``, the hidden state matrix |
| 87 | + after processing the last token in the sequence. |
| 88 | + |
| 89 | + |
| 90 | +**Types** |
| 91 | + |
| 92 | +* *T*: any supported floating-point type. |
| 93 | + |
| 94 | + |
| 95 | +**Example** |
| 96 | + |
| 97 | +.. code-block:: xml |
| 98 | + :force: |
| 99 | +
|
| 100 | + <layer ... type="GatedDeltaNet" ...> |
| 101 | + <input> |
| 102 | + <port id="0"> <!-- `query` --> |
| 103 | + <dim>1</dim> |
| 104 | + <dim>16</dim> |
| 105 | + <dim>8</dim> |
| 106 | + <dim>64</dim> |
| 107 | + </port> |
| 108 | + <port id="1"> <!-- `key` --> |
| 109 | + <dim>1</dim> |
| 110 | + <dim>16</dim> |
| 111 | + <dim>8</dim> |
| 112 | + <dim>64</dim> |
| 113 | + </port> |
| 114 | + <port id="2"> <!-- `value` --> |
| 115 | + <dim>1</dim> |
| 116 | + <dim>16</dim> |
| 117 | + <dim>8</dim> |
| 118 | + <dim>128</dim> |
| 119 | + </port> |
| 120 | + <port id="3"> <!-- `recurrent_state` --> |
| 121 | + <dim>1</dim> |
| 122 | + <dim>8</dim> |
| 123 | + <dim>64</dim> |
| 124 | + <dim>128</dim> |
| 125 | + </port> |
| 126 | + <port id="4"> <!-- `gate` --> |
| 127 | + <dim>1</dim> |
| 128 | + <dim>16</dim> |
| 129 | + <dim>8</dim> |
| 130 | + </port> |
| 131 | + <port id="5"> <!-- `beta` --> |
| 132 | + <dim>1</dim> |
| 133 | + <dim>16</dim> |
| 134 | + <dim>8</dim> |
| 135 | + </port> |
| 136 | + </input> |
| 137 | + <output> |
| 138 | + <port id="6"> <!-- `output_attn` --> |
| 139 | + <dim>1</dim> |
| 140 | + <dim>16</dim> |
| 141 | + <dim>8</dim> |
| 142 | + <dim>128</dim> |
| 143 | + </port> |
| 144 | + <port id="7"> <!-- `output_recurrent_state` --> |
| 145 | + <dim>1</dim> |
| 146 | + <dim>8</dim> |
| 147 | + <dim>64</dim> |
| 148 | + <dim>128</dim> |
| 149 | + </port> |
| 150 | + </output> |
| 151 | + </layer> |
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