[Frontend, pytorch] Vc/pytorch lstm (apache#8447)

* lstm layer conversion to relay from pytorch model (TorchScript) was supported

* bidirectional LSTM layer was supported for pytorch API

* lstm tests were implemented. fixes in pytorch lstm

* fix pytorch bidirectional lstm. update test comment

* black format and some small fixes

* LSTM with projection was supported for pytorch frontend. test was updated by new combination of LSTM types

* lint fixes

* add bias switcher for LSTM types test. fix LSTM implementation in pytorch frontend for case without biases. exception in the test for conversion LSTM with projection from pytorch to ONNX

* transfer test_lstms to pytest format

* onnx model saving was implemented through io.BytesIO. creating/removing tmp dir was removed. remove unneccessary comments

* gpu target was added to the test

Co-authored-by: Valery Chernov <valery.chernov@deelvin.com>

python/tvm/relay/frontend/pytorch.py

@@ -41,6 +41,7 @@
 from . import qnn_torch
 from .common import AttrCvt, get_relay_op
 from .common import infer_value as _infer_value
+from .common import infer_shape as _infer_shape
 from .common import infer_value_simulated as _infer_value_simulated
 from .common import try_infer_value
 from .pytorch_utils import is_version_greater_than
@@ -2338,6 +2339,298 @@ def flip(self, inputs, input_types):
         axis = inputs[1]
         return _op.transform.reverse(data, axis=axis[0])
 
+    def lstm_cell(self, input_seqs, hidden, weights, has_proj=False):
+        if has_proj:
+            assert len(weights) == 5
+        else:
+            assert len(weights) == 4
+        outputs_list = []
+        # Default activations types
+        f_act = _op.sigmoid
+        g_act = _op.tanh
+        h_act = _op.tanh
+
+        # Input hiddens
+        H_t = hidden[0]  # (batch, hidden_size)
+        C_t = hidden[1]  # (batch, hidden_size)
+        for x_t in input_seqs:
+            # x_t shape = (batch, feature size)
+            # gates shape = (batch, 4 * hidden_size)
+            gates = _op.nn.dense(x_t, weights[0]) + _op.nn.dense(H_t, weights[1])
+            # Add biases
+            if weights[2] is not None:
+                gates += weights[2]
+            if weights[3] is not None:
+                gates += weights[3]
+            i, f, c, o = _op.split(gates, 4, axis=-1)  # (batch, hidden_size)
+
+            i = f_act(i)
+            f = f_act(f)
+            c = g_act(c)
+            o = f_act(o)
+
+            C = f * C_t + i * c
+            H = o * h_act(C)
+
+            if has_proj:
+                H = _op.nn.dense(H, weights[4])
+
+            H_t = H
+            C_t = C
+            outputs_list.append(H)  # [seq_num, (batch, hidden_size)]
+        hidden_outputs = (H_t, C_t)
+
+        return (outputs_list, hidden_outputs)
+
+    def bidir_lstm_cell(self, input_seq, hidden_pair, weights_pair, has_proj=False):
+        fw_outputs = self.lstm_cell(input_seq, hidden_pair[0], weights_pair[0], has_proj)
+
+        rev_input_seq = []
+        seq_len = len(input_seq)
+        for i in range(seq_len):
+            rev_input_seq.append(input_seq[seq_len - 1 - i])  # [seq_num, (batch, hidden_size)]
+        rev_outputs = self.lstm_cell(rev_input_seq, hidden_pair[1], weights_pair[1], has_proj)
+
+        final_outputs = []  # [seq_num, (batch, 2 * hidden_size)]
+        for j in range(seq_len):
+            final_outputs.append(
+                _op.concatenate([fw_outputs[0][j], rev_outputs[0][seq_len - 1 - j]], -1)
+            )
+
+        return final_outputs, (fw_outputs[1], rev_outputs[1])
+
+    def lstm_layers(
+        self, input_data, hiddens, weights, bidirectional, dtype, dropout_p=0.0, has_proj=False
+    ):
+        hidden_layers_num = len(hiddens)
+        assert len(weights) == hidden_layers_num
+
+        # split input sequence to samples set
+        input_seqs = self.unbind((input_data, 0), dtype)  # [seq_num, (batch, feature_size)]
+        output_hiddens = []
+        for k in range(hidden_layers_num):
+            hiddens_input = hiddens[k]
+            weights_input = weights[k]
+
+            outputs = (
+                self.bidir_lstm_cell(input_seqs, hiddens_input, weights_input, has_proj)
+                if bidirectional
+                else self.lstm_cell(input_seqs, hiddens_input, weights_input, has_proj)
+            )
+
+            output_hiddens.append(outputs[1])
+            # input_seqs shape = [seq_num, (batch, feature_size)] or
+            # [seq_num, (batch, 2*feature_size)] for bidirectional
+            input_seqs = outputs[0]
+
+            # TODO (vvchernov): in pytorch implementation train is also checked
+            # see https://github.com/pytorch/pytorch/blob/70c8daf43946b53af6493d058899ef952d27d339
+            # /aten/src/ATen/native/RNN.cpp#L1054
+            if dropout_p != 0 and k < hidden_layers_num - 1:
+                # for input in input_seqs:
+                #     input = _op.dropout(input, dropout_p)
+                raise NotImplementedError("Dropout for LSTM has not been supported yet!")
+        final_hiddens = []
+        if bidirectional:
+            for i in range(hidden_layers_num):
+                final_hiddens.append(output_hiddens[i][0])
+                final_hiddens.append(output_hiddens[i][1])
+        else:
+            final_hiddens = output_hiddens
+
+        return _op.stack(input_seqs, 0), final_hiddens
+
+    def lstm(self, inputs, input_types):
+        """
+        Description of LSTM in pytorch:https://pytorch.org/docs/stable/generated/torch.nn.LSTM.html
+        Native implementation for torch version less than 1.8.0 (projection is unsupported):
+        https://github.com/pytorch/pytorch/blob/70c8daf43946b53af6493d058899ef952d27d339/aten/ \
+        src/ATen/native/RNN.cpp#L1396
+        Native implementation for torch version from 1.8.0 and higher (projection is supported):
+        https://github.com/pytorch/pytorch/blob/master/aten/src/ATen/native/RNN.cpp#L1483
+        """
+        # TODO (vvchernov): support dropout
+        assert len(inputs) == 9, "Input of size 9 is expected"
+        # Unpack inputs, note that if optional and not provided then value will be None.
+        _X = inputs[0]
+        # _X shape (seq_num, batch, feature_size) or (batch, seq_num, feature_size)
+
+        hidden_states = inputs[1]
+        assert len(hidden_states) == 2, "lstm expects two hidden states"
+        h_0 = hidden_states[0]
+        c_0 = hidden_states[1]
+        # H0 shape (hidden_layers_num, batch, proj_size) if projection
+        # else (hidden_layers_num, batch, hidden_size)
+        # C0 shape (hidden_layers_num, batch, hidden_size)
+
+        _weights = inputs[2]
+        # If no projection
+        # Wi layer[0] shape (4 * hidden_size, feature_size)
+        # Wh layer[0] shape (4 * hidden_size, hidden_size)
+        # Bi layer[0] shape (4 * hidden_size)
+        # Bh layer[0] shape (4 * hidden_size)
+
+        # Wi layer[>0] shape (4 * hidden_size, hidden_size * num_directions)
+        # Wh layer[>0] shape (4 * hidden_size, hidden_size)
+        # Bi layer[>0] shape (4 * hidden_size)
+        # Bh layer[>0] shape (4 * hidden_size)
+
+        # If projection
+        # Wi layer[0] shape (4 * hidden_size, feature_size)
+        # Wh layer[0] shape (4 * hidden_size, proj_size)
+        # Bi layer[0] shape (4 * hidden_size)
+        # Bh layer[0] shape (4 * hidden_size)
+        # P  layer[0] shape (proj_size, hidden_size)
+
+        # Wi layer[>0] shape (4 * hidden_size, proj_size * num_directions)
+        # Wh layer[>0] shape (4 * hidden_size, proj_size)
+        # Bi layer[>0] shape (4 * hidden_size)
+        # Bh layer[>0] shape (4 * hidden_size)
+        # P  layer[>0] shape (proj_size, hidden_size)
+
+        # Scalar inputs
+        has_biases = inputs[3]
+        num_layers = inputs[4]
+        dropout_p = inputs[5]  # dropout probability, if 0.0 it means there is no dropout
+        # train = inputs[6]
+        bidirectional = inputs[7]
+        batch_first = inputs[8]
+
+        num_directions = 1
+        if bidirectional:
+            num_directions = 2
+
+        rsd = len(_weights) % num_layers
+        assert rsd == 0, "The number of weights must be a multiple of the number of layers!"
+        rsd = (len(_weights) / num_layers) % num_directions
+        assert (
+            rsd == 0
+        ), "The number of weights in layer must be a multiple of the number of directions!"
+        has_proj = False
+        proj_size = 0
+        weights_num = int(len(_weights) / num_layers / num_directions)
+        if has_biases:
+            if weights_num == 5:
+                has_proj = True
+                proj_size = _infer_shape(_weights[4])[0]
+            else:
+                assert weights_num == 4, "The weights number in layer is expected equal to 4"
+        else:
+            if weights_num == 3:
+                has_proj = True
+                proj_size = _infer_shape(_weights[2])[0]
+            else:
+                assert weights_num == 2, "The weights number in layer is expected equal to 2"
+
+        weights = []
+        if has_biases:
+            if bidirectional:
+                rsd = len(_weights) % (2 * weights_num)
+                assert rsd == 0, "got an incorrect number of LSTM weights"
+                for i in range(0, len(_weights), 2 * weights_num):
+                    fw_weights = []
+                    rev_weights = []
+                    for j in range(weights_num):
+                        fw_weights.append(_weights[i + j])
+                        rev_weights.append(_weights[i + j + weights_num])
+                    weights.append((fw_weights, rev_weights))
+            else:
+                assert len(_weights) % weights_num == 0, "got an incorrect number of LSTM weights"
+                for i in range(0, len(_weights), weights_num):
+                    fw_weights = []
+                    for j in range(weights_num):
+                        fw_weights.append(_weights[i + j])
+                    weights.append(fw_weights)
+        else:
+            if bidirectional:
+                rsd = len(_weights) % (2 * weights_num)
+                assert rsd == 0, "got an incorrect number of LSTM weights"
+                for i in range(0, len(_weights), 2 * weights_num):
+                    fw_weights = []
+                    rev_weights = []
+                    k = i + weights_num
+                    if has_proj:
+                        fw_weights = [_weights[i], _weights[i + 1], None, None, _weights[i + 2]]
+                        rev_weights = [_weights[k], _weights[k + 1], None, None, _weights[k + 2]]
+                    else:
+                        fw_weights = [_weights[i], _weights[i + 1], None, None]
+                        rev_weights = [_weights[k], _weights[k + 1], None, None]
+                    weights.append((fw_weights, rev_weights))
+            else:
+                assert len(_weights) % weights_num == 0, "got an incorrect number of LSTM weights"
+                for i in range(0, len(_weights), weights_num):
+                    if has_proj:
+                        fw_weights = [_weights[i], _weights[i + 1], None, None, _weights[i + 2]]
+                    else:
+                        fw_weights = [_weights[i], _weights[i + 1], None, None]
+                    weights.append(fw_weights)
+        assert (
+            len(weights) == num_layers
+        ), "For stacked LSTM number of weights tuples should be the same as number of layers!"
+
+        X = _op.transpose(_X, (1, 0, 2)) if batch_first else _X
+        # TODO (vvchernov): Which data type should be used? from input or weights?
+        # Instead of it _infer_type(X).checked_type.dtype can be used
+        X_dtype = input_types[0]
+        X_shape = _infer_shape(X)  # (seq_num, batch, feature_size)
+
+        hidden_size = _infer_shape(_weights[0])[0] / 4
+        batch_size = X_shape[1]
+
+        # Initialize hidden states if not provided.
+        layers_h = []
+        layers_c = []
+        hidden_layers_num = num_directions * num_layers
+        if h_0 is None:
+            if has_proj:
+                h_0 = _op.zeros((batch_size, proj_size), X_dtype)
+            else:
+                h_0 = _op.zeros((batch_size, hidden_size), X_dtype)
+            for i in range(hidden_layers_num):
+                layers_h.append(h_0)
+        else:
+            layers_h = self.unbind((h_0, 0), X_dtype)
+        if c_0 is None:
+            c_0 = _op.zeros((batch_size, hidden_size), X_dtype)
+            for i in range(hidden_layers_num):
+                layers_c.append(c_0)
+        else:
+            layers_c = self.unbind((c_0, 0), X_dtype)
+
+        hiddens = []
+        for i in range(num_layers):
+            if bidirectional:
+                hiddens.append(
+                    ((layers_h[2 * i], layers_c[2 * i]), (layers_h[2 * i + 1], layers_c[2 * i + 1]))
+                )
+            else:
+                hiddens.append((layers_h[i], layers_c[i]))
+
+        outputs = self.lstm_layers(
+            X,
+            hiddens,
+            weights,
+            bidirectional,
+            dtype=X_dtype,
+            dropout_p=dropout_p,
+            has_proj=has_proj,
+        )
+
+        # output shape = (seq_num, batch, hidden_size) or
+        # (seq_num, batch, 2*feature_size) for bidirectional
+        output = outputs[0]
+
+        hy = []
+        cy = []
+        for hidden in outputs[1]:
+            hy.append(hidden[0])
+            cy.append(hidden[1])
+
+        if batch_first:
+            output = _op.transpose(output, (1, 0, 2))
+
+        return (output, _op.stack(hy, 0), _op.stack(cy, 0))
+
     # Operator mappings
     def create_convert_map(self):
         self.convert_map = {
@@ -2554,6 +2847,7 @@ def create_convert_map(self):
             "aten::nll_loss": self.nll_loss,
             "aten::nll_loss2d": self.nll_loss,
             "aten::flip": self.flip,
+            "aten::lstm": self.lstm,
         }
 
     def update_convert_map(self, custom_map):