[WIP] Add Numpy Backend

keras_core/applications/applications_test.py

@@ -107,6 +107,10 @@ def _get_elephant(target_size):
     os.environ.get("SKIP_APPLICATIONS_TESTS"),
     reason="Env variable set to skip.",
 )
+@pytest.mark.skipif(
+    backend.backend() == "numpy",
+    reason="Trainer not implemented from NumPy backend.",
+)
 class ApplicationsTest(testing.TestCase, parameterized.TestCase):
     @parameterized.named_parameters(MODEL_LIST)
     def test_application_notop_variable_input_channels(self, app, last_dim, _):

keras_core/applications/imagenet_utils_test.py

@@ -1,7 +1,9 @@
 import numpy as np
+import pytest
 from absl.testing import parameterized
 
 import keras_core as keras
+from keras_core import backend
 from keras_core import testing
 from keras_core.applications import imagenet_utils as utils
 from keras_core.mixed_precision import set_dtype_policy
@@ -74,6 +76,10 @@ def test_preprocess_input(self):
             {"testcase_name": "mode_caffe", "mode": "caffe"},
         ]
     )
+    @pytest.mark.skipif(
+        backend.backend() == "numpy",
+        reason="Trainer not implemented from NumPy backend.",
+    )
     def test_preprocess_input_symbolic(self, mode):
         # Test image batch
         x = np.random.uniform(0, 255, (2, 10, 10, 3))

keras_core/backend/__init__.py

@@ -37,5 +37,8 @@
 elif backend() == "torch":
     print_msg("Using PyTorch backend.")
     from keras_core.backend.torch import *  # noqa: F403
+elif backend() == "numpy":
+    print_msg("Using NumPy backend.")
+    from keras_core.backend.numpy import *  # noqa: F403
 else:
     raise ValueError(f"Unable to import backend : {backend()}")

keras_core/backend/numpy/__init__.py

@@ -0,0 +1,20 @@
+from keras_core.backend.numpy import core
+from keras_core.backend.numpy import image
+from keras_core.backend.numpy import math
+from keras_core.backend.numpy import nn
+from keras_core.backend.numpy import numpy
+from keras_core.backend.numpy import random
+from keras_core.backend.numpy.core import DYNAMIC_SHAPES_OK
+from keras_core.backend.numpy.core import Variable
+from keras_core.backend.numpy.core import cast
+from keras_core.backend.numpy.core import compute_output_spec
+from keras_core.backend.numpy.core import cond
+from keras_core.backend.numpy.core import convert_to_numpy
+from keras_core.backend.numpy.core import convert_to_tensor
+from keras_core.backend.numpy.core import is_tensor
+from keras_core.backend.numpy.core import name_scope
+from keras_core.backend.numpy.core import shape
+from keras_core.backend.numpy.core import vectorized_map
+from keras_core.backend.numpy.rnn import gru
+from keras_core.backend.numpy.rnn import lstm
+from keras_core.backend.numpy.rnn import rnn

keras_core/backend/numpy/core.py

@@ -0,0 +1,214 @@
+from contextlib import nullcontext
+
+import numpy as np
+from tensorflow import nest
+
+from keras_core.backend.common import KerasVariable
+from keras_core.backend.common import standardize_dtype
+from keras_core.backend.common.keras_tensor import KerasTensor
+from keras_core.backend.common.stateless_scope import StatelessScope
+
+DYNAMIC_SHAPES_OK = True
+
+
+class Variable(KerasVariable):
+    def _initialize(self, value):
+        self._value = np.array(value, dtype=self._dtype)
+
+    def _direct_assign(self, value):
+        self._value = np.array(value, dtype=self._dtype)
+
+    def _convert_to_tensor(self, value, dtype=None):
+        return convert_to_tensor(value, dtype=dtype)
+
+    # Overload native accessor.
+    def __array__(self):
+        return self.value
+
+
+def convert_to_tensor(x, dtype=None):
+    if dtype is not None:
+        dtype = standardize_dtype(dtype)
+    if isinstance(x, Variable):
+        if dtype and dtype != x.dtype:
+            return x.value.astype(dtype)
+        return x.value
+    return np.array(x, dtype=dtype)
+
+
+def convert_to_numpy(x):
+    return np.array(x)
+
+
+def is_tensor(x):
+    if isinstance(x, (np.generic, np.ndarray)):
+        return True
+    return False
+
+
+def shape(x):
+    # This will work as long as we disallow
+    # dynamic shapes in NumPy.
+    return x.shape
+
+
+def cast(x, dtype):
+    return convert_to_tensor(x, dtype=dtype)
+
+
+def cond(pred, true_fn, false_fn):
+    if pred:
+        return true_fn()
+    return false_fn()
+
+
+def name_scope(name):
+    # There is no need for a named context for NumPy.
+    return nullcontext()
+
+
+def vectorized_map(function, elements):
+    if len(elements) == 1:
+        return function(elements)
+    else:
+        batch_size = elements[0].shape[0]
+        output_store = list()
+        for index in range(batch_size):
+            output_store.append(function([x[index] for x in elements]))
+        return np.stack(output_store)
+
+
+# Shape / dtype inference util
+def compute_output_spec(fn, *args, **kwargs):
+    with StatelessScope():
+
+        def has_none_shape(x):
+            if isinstance(x, KerasTensor):
+                return None in x.shape
+            return False
+
+        none_in_shape = any(map(has_none_shape, nest.flatten((args, kwargs))))
+
+        def convert_keras_tensor_to_numpy(x, fill_value=None):
+            if isinstance(x, KerasTensor):
+                shape = list(x.shape)
+                if fill_value:
+                    for i, e in enumerate(shape):
+                        if e is None:
+                            shape[i] = fill_value
+                return np.empty(
+                    shape=shape,
+                    dtype=x.dtype,
+                )
+            return x
+
+        args_1, kwargs_1 = nest.map_structure(
+            lambda x: convert_keras_tensor_to_numpy(x, fill_value=83),
+            (args, kwargs),
+        )
+        outputs_1 = fn(*args_1, **kwargs_1)
+
+        outputs = outputs_1
+
+        if none_in_shape:
+            args_2, kwargs_2 = nest.map_structure(
+                lambda x: convert_keras_tensor_to_numpy(x, fill_value=89),
+                (args, kwargs),
+            )
+            outputs_2 = fn(*args_2, **kwargs_2)
+
+            flat_out_1 = nest.flatten(outputs_1)
+            flat_out_2 = nest.flatten(outputs_2)
+
+            flat_out = []
+            for x1, x2 in zip(flat_out_1, flat_out_2):
+                shape = list(x1.shape)
+                for i, e in enumerate(x2.shape):
+                    if e != shape[i]:
+                        shape[i] = None
+                flat_out.append(KerasTensor(shape, standardize_dtype(x1.dtype)))
+            outputs = nest.pack_sequence_as(outputs_1, flat_out)
+
+        def convert_numpy_to_keras_tensor(x):
+            if is_tensor(x):
+                return KerasTensor(x.shape, standardize_dtype(x.dtype))
+            return x
+
+        output_spec = nest.map_structure(convert_numpy_to_keras_tensor, outputs)
+    return output_spec
+
+
+def scatter(indices, values, shape):
+    indices = convert_to_tensor(indices)
+    values = convert_to_tensor(values)
+    zeros = np.zeros(shape, dtype=values.dtype)
+
+    index_length = indices.shape[-1]
+    value_shape = shape[index_length:]
+    indices = np.reshape(indices, [-1, index_length])
+    values = np.reshape(values, [-1] + list(value_shape))
+
+    for i in range(indices.shape[0]):
+        index = indices[i]
+        zeros[tuple(index)] += values[i]
+    return zeros
+
+
+def scatter_update(inputs, indices, updates):
+    indices = np.array(indices)
+    indices = np.transpose(indices)
+    inputs[tuple(indices)] = updates
+    return inputs
+
+
+def slice(inputs, start_indices, lengths):
+    # Validate inputs
+    assert len(start_indices) == len(lengths)
+
+    # Generate list of indices arrays for each dimension
+    indices = [
+        np.arange(start, start + length)
+        for start, length in zip(start_indices, lengths)
+    ]
+
+    # Use np.ix_ to create a multidimensional index array
+    mesh = np.ix_(*indices)
+
+    return inputs[mesh]
+
+
+def slice_update(inputs, start_indices, updates):
+    # Generate list of indices arrays for each dimension
+    indices = [
+        np.arange(start, start + length)
+        for start, length in zip(start_indices, updates.shape)
+    ]
+
+    # Use np.ix_ to create a multidimensional index array
+    mesh = np.ix_(*indices)
+    inputs[mesh] = updates
+    return inputs
+
+
+def while_loop(
+    cond,
+    body,
+    loop_vars,
+    maximum_iterations=None,
+):
+    current_iter = 0
+    iteration_check = (
+        lambda iter: maximum_iterations is None or iter < maximum_iterations
+    )
+    loop_vars = tuple([convert_to_tensor(v) for v in loop_vars])
+    while cond(*loop_vars) and iteration_check(current_iter):
+        loop_vars = body(*loop_vars)
+        if not isinstance(loop_vars, (list, tuple)):
+            loop_vars = (loop_vars,)
+        loop_vars = tuple(loop_vars)
+        current_iter += 1
+    return loop_vars
+
+
+def stop_gradient():
+    raise NotADirectoryError("stop_gradient is not implemented for NumPy.")

keras_core/backend/numpy/image.py

@@ -0,0 +1,45 @@
+import jax
+import numpy as np
+
+RESIZE_METHODS = (
+    "bilinear",
+    "nearest",
+    "lanczos3",
+    "lanczos5",
+    "bicubic",
+)
+
+
+def resize(
+    image, size, method="bilinear", antialias=False, data_format="channels_last"
+):
+    if method not in RESIZE_METHODS:
+        raise ValueError(
+            "Invalid value for argument `method`. Expected of one "
+            f"{RESIZE_METHODS}. Received: method={method}"
+        )
+    if not len(size) == 2:
+        raise ValueError(
+            "Argument `size` must be a tuple of two elements "
+            f"(height, width). Received: size={size}"
+        )
+    size = tuple(size)
+    if len(image.shape) == 4:
+        if data_format == "channels_last":
+            size = (image.shape[0],) + size + (image.shape[-1],)
+        else:
+            size = (image.shape[0], image.shape[1]) + size
+    elif len(image.shape) == 3:
+        if data_format == "channels_last":
+            size = size + (image.shape[-1],)
+        else:
+            size = (image.shape[0],) + size
+    else:
+        raise ValueError(
+            "Invalid input rank: expected rank 3 (single image) "
+            "or rank 4 (batch of images). Received input with shape: "
+            f"image.shape={image.shape}"
+        )
+    return np.array(
+        jax.image.resize(image, size, method=method, antialias=antialias)
+    )

keras_core/backend/numpy/layer.py

@@ -0,0 +1,3 @@
+class NumpyLayer:
+    def _post_build(self):
+        pass