cifar10 training

experiments/mnist/cifar_training.py

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+# Copyright 2018 The JAX Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""A basic MNIST example using Numpy and JAX.
+
+The primary aim here is simplicity and minimal dependencies.
+"""
+
+
+import time
+
+import datasets
+import jax
+import jax.numpy as jnp
+import numpy as np
+import numpy.random as npr
+from jax import grad, jit, lax
+
+import jax_scaled_arithmetics as jsa
+
+
+def logsumexp(a, axis=None, keepdims=False):
+    dims = (axis,)
+    amax = jnp.max(a, axis=dims, keepdims=keepdims)
+    # FIXME: not proper scale propagation, introducing NaNs
+    # amax = lax.stop_gradient(lax.select(jnp.isfinite(amax), amax, lax.full_like(amax, 0)))
+    amax = lax.stop_gradient(amax)
+    out = lax.sub(a, amax)
+    out = lax.exp(out)
+    out = lax.add(lax.log(jnp.sum(out, axis=dims, keepdims=keepdims)), amax)
+    return out
+
+
+def init_random_params(scale, layer_sizes, rng=npr.RandomState(0)):
+    return [(scale * rng.randn(m, n), scale * rng.randn(n)) for m, n, in zip(layer_sizes[:-1], layer_sizes[1:])]
+
+
+def print_mean_std(name, v):
+    data, scale = jsa.lax.get_data_scale(v)
+    # Always use np.float32, to avoid floating errors in descaling + stats.
+    v = jsa.asarray(data, dtype=np.float32)
+    m, s = np.mean(v), np.std(v)
+    # print(data)
+    print(f"{name}: MEAN({m:.4f}) / STD({s:.4f}) / SCALE({scale:.4f})")
+
+
+def predict(params, inputs):
+    activations = inputs
+    for w, b in params[:-1]:
+        # Matmul + relu
+        outputs = jnp.dot(activations, w) + b
+        activations = jnp.maximum(outputs, 0)
+
+    final_w, final_b = params[-1]
+    logits = jnp.dot(activations, final_w) + final_b
+
+    # Dynamic rescaling of the gradient, as logits gradient not properly scaled.
+    logits = jsa.ops.dynamic_rescale_l2_grad(logits)
+    output = logits - logsumexp(logits, axis=1, keepdims=True)
+
+    return output
+
+
+def loss(params, batch):
+    inputs, targets = batch
+    preds = predict(params, inputs)
+    return -jnp.mean(jnp.sum(preds * targets, axis=1))
+
+
+def accuracy(params, batch):
+    inputs, targets = batch
+    target_class = jnp.argmax(targets, axis=1)
+    predicted_class = jnp.argmax(predict(params, inputs), axis=1)
+    return jnp.mean(predicted_class == target_class)
+
+
+if __name__ == "__main__":
+    width = 2048
+    lr = 1e-4
+    use_autoscale = True
+    autoscale = jsa.autoscale if use_autoscale else lambda f: f
+
+    layer_sizes = [3072, width, width, 10]
+    param_scale = 1.0
+
+    step_size = lr
+    num_epochs = 10
+    batch_size = 128
+    training_dtype = np.float16
+    scale_dtype = np.float32
+
+    train_images, train_labels, test_images, test_labels = datasets.cifar()
+    num_train = train_images.shape[0]
+    num_complete_batches, leftover = divmod(num_train, batch_size)
+    num_batches = num_complete_batches + bool(leftover)
+
+    def data_stream():
+        rng = npr.RandomState(0)
+        while True:
+            perm = rng.permutation(num_train)
+            for i in range(num_batches):
+                batch_idx = perm[i * batch_size : (i + 1) * batch_size]
+                yield train_images[batch_idx], train_labels[batch_idx]
+
+    batches = data_stream()
+    params = init_random_params(param_scale, layer_sizes)
+    # Transform parameters to `ScaledArray` and proper dtype.
+    if use_autoscale:
+        params = jsa.as_scaled_array(params, scale=scale_dtype(param_scale))
+    params = jax.tree_map(lambda v: v.astype(training_dtype), params, is_leaf=jsa.core.is_scaled_leaf)
+
+    @jit
+    @autoscale
+    def update(params, batch):
+        grads = grad(loss)(params, batch)
+        return [(w - step_size * dw, b - step_size * db) for (w, b), (dw, db) in zip(params, grads)]
+
+    for epoch in range(num_epochs):
+        start_time = time.time()
+        for _ in range(num_batches):
+            batch = next(batches)
+            # Scaled micro-batch + training dtype cast.
+            if use_autoscale:
+                batch = jsa.as_scaled_array(batch, scale=scale_dtype(param_scale))
+            batch = jax.tree_map(lambda v: v.astype(training_dtype), batch, is_leaf=jsa.core.is_scaled_leaf)
+
+            with jsa.AutoScaleConfig(rounding_mode=jsa.Pow2RoundMode.DOWN, scale_dtype=scale_dtype):
+                params = update(params, batch)
+
+        epoch_time = time.time() - start_time
+
+        # Evaluation in float32, for consistency.
+        raw_params = jsa.asarray(params, dtype=np.float32)
+        train_acc = accuracy(raw_params, (train_images, train_labels))
+        test_acc = accuracy(raw_params, (test_images, test_labels))
+        print(f"Epoch {epoch} in {epoch_time:0.2f} sec")
+        print(f"Training set accuracy {train_acc:0.5f}")
+        print(f"Test set accuracy {test_acc:0.5f}")