better repalce_node fn

hls4ml/model/graph.py

@@ -573,13 +573,24 @@ def replace_node(self, old_node, new_node):
             new_node (Layer): The new node
 
         """
-        prev_node = self.graph.get(old_node.inputs[0])
-        next_node = next((x for x in self.graph.values() if x.inputs[0] == old_node.outputs[0]), None)
-        if next_node is not None:
-            next_node.inputs[0] = new_node.outputs[0]
-        if prev_node is not None:
-            if new_node.inputs is None or len(new_node.inputs) == 0:  # Check if already rewired
-                new_node.inputs = [prev_node.outputs[0]]
+
+        # fmt: off
+        assert len(new_node.inputs) == len(old_node.inputs), \
+            f'{new_node.name} and {old_node.name} have different number of inputs'
+        assert len(new_node.outputs) == len(old_node.outputs), \
+            f'{new_node.name} and {old_node.name} have different number of outputs'
+        # fmt: on
+
+        repl = {old_name: new_name for old_name, new_name in zip(old_node.outputs, new_node.outputs)}
+        repl.update({old_name: new_name for old_name, new_name in zip(old_node.inputs, new_node.inputs)})
+
+        for node in self.graph.values():
+            for i, n in enumerate(node.inputs):
+                if n in repl:
+                    node.inputs[i] = repl[n]
+            for i, n in enumerate(node.outputs):
+                if n in repl:
+                    node.outputs[i] = repl[n]
 
         self.graph = OrderedDict((new_node.name, new_node) if k == old_node.name else (k, v) for k, v in self.graph.items())
         self._update_model_outputs()
@@ -644,7 +655,9 @@ def compile(self):
         Users should call this function if they want to use `predict` functionality for simulation.
         """
         self.write()
+        self._compile()
 
+    def _compile(self):
         lib_name = self.config.backend.compile(self)
         if self._top_function_lib is not None:
             if platform.system() == "Linux":

test/pytest/test_repack_stream.py

@@ -0,0 +1,62 @@
+from pathlib import Path
+
+import numpy as np
+import pytest
+from tensorflow import keras
+
+from hls4ml.converters import convert_from_keras_model
+
+# test_root_path = Path(__file__).parent
+test_root_path = Path('/tmp')
+
+
+def test_repack_precision():
+    inp = keras.Input(shape=(3, 3), name='inp')
+    out = keras.layers.Reshape((3, 3), name='reshape')(inp)
+    out = keras.layers.Conv1D(2, 2, name='conv')(out)
+    model = keras.Model(inp, out)
+
+    layer_conf = {
+        'inp': {'Precision': 'fixed<20,10>'},
+        'reshape': {'Precision': 'fixed<20,10>'},
+        'conv': {'Precision': 'fixed<20,10>'},
+    }
+
+    hls_config = {'Model': {'Precision': 'fixed<2,1>', 'ReuseFactor': 1}, 'LayerName': layer_conf}
+
+    # Repack only happens in io_stream
+    model_hls = convert_from_keras_model(model, hls_config=hls_config, io_type='io_stream')
+    assert 'repack_reshape' in model_hls.graph, 'repack_reshape not found in graph'
+    repack_precision = model_hls.graph['repack_reshape'].attributes['result_t'].precision
+    assert repack_precision.integer == 10, 'Precision mismatch'
+    assert repack_precision.fractional == 10, 'Precision mismatch'
+    assert repack_precision.width == 20, 'Precision mismatch'
+    assert repack_precision.signed is True, 'Precision mismatch'
+
+
+@pytest.mark.parametrize('backend', ['vivado', 'vitis', 'quartus'])
+@pytest.mark.parametrize('strategy', ['Latency', 'Resource'])
+def test_repack(backend: str, strategy: str):
+    inp1 = keras.Input(shape=(4,), name='inp1')
+    inp2 = keras.Input(shape=(4,), name='inp2')
+    r1 = keras.layers.Reshape((2, 2), name='reshape1')(inp1)
+    r2 = keras.layers.Reshape((2, 2), name='reshape2')(inp2)
+    out = keras.layers.Concatenate(name='concat')([r1, r2])
+    model = keras.Model([inp1, inp2], out)
+
+    hls_config = {'Model': {'Precision': 'ap_ufixed<8,8>', 'ReuseFactor': 1}, 'Strategy': strategy}
+    model_hls = convert_from_keras_model(
+        model,
+        io_type='io_stream',
+        backend='Vivado',
+        hls_config=hls_config,
+        output_dir=str(test_root_path / f'{backend}_{strategy}'),
+    )
+    model_hls.compile()
+    inp_data = [
+        np.random.randint(0, 2**8, (100, 4)).astype(np.float32),
+        np.random.randint(0, 2**8, (100, 4)).astype(np.float32),
+    ]
+    out_target = np.concatenate([inp_data[0].reshape(100, 2, 2), inp_data[1].reshape(100, 2, 2)], axis=-1)
+    out_data: np.ndarray = model_hls.predict(inp_data)  # type: ignore
+    assert np.all(out_data.reshape(out_target.shape) == out_target), 'Concatenate failed: mismatching output'