tests/pkg_emlearn: add sample application

tests/pkg_emlearn/.gitignore

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+model.h
+tmp/

tests/pkg_emlearn/Makefile

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+include ../Makefile.tests_common
+
+USEPKG += emlearn
+
+BLOBS += digit
+
+BUILDDEPS += model.h
+
+include $(RIOTBASE)/Makefile.include
+
+model.h: $(CURDIR)/model
+	$(Q)$(CURDIR)/generate_model.py
+	$(Q)echo "/* fix for no newline at eof */\n" >> model.h

tests/pkg_emlearn/README.md

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+## Emlearn package test application
+
+This application shows how to use a machine learning model with emlearn on RIOT
+in order to predict a value from a hand written digit image.
+The model is a [Scikit-Learn](https://scikit-learn.org) random forest estimator
+trained on the MNIST dataset.
+
+### Expected output
+
+The default digit to predict is a hand-written '6', so the application output
+is the following:
+
+```
+Predicted digit: 6
+```
+
+### Use the Python scripts
+
+The application comes with 3 Python scripts:
+- `generate_digit.py` is used to generate a new digit file. This file is
+  embedded in the firmware image and is used as input for the inference engine.
+  Use the `-i` option to select a different digit.
+  For example, the following command:
+  ```
+  $ ./generate_digit.py -i 1
+  ```
+  will generate a digit containing a '9'.
+  The digit is displayed at the end of the script so one knows which digit is
+  stored.
+  Note that each time a new digit is generated, the firmware image must be
+  rebuilt to include this new digit.
+- `train_model.py` is used to train a new Scikit-Learn Random Forest estimator.
+  The trained model is stored in the `model` binary file.
+  ```
+  $ ./train_model.py
+  ```
+  will just train the model.
+- `generate_model.py` is used to generate the `sonar.h` header file from the
+  `model` binary file. The script is called automatically by the build system
+  when the `model` binary file is updated.

tests/pkg_emlearn/generate_digit.py

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+#!/usr/bin/env python3
+
+"""Generate a binary file from a sample image of the MNIST dataset.
+Pixel of the sample are stored as float32, images have size 8x8.
+"""
+
+import os
+import argparse
+
+import numpy as np
+import matplotlib.pyplot as plt
+
+from sklearn.model_selection import train_test_split
+from sklearn import datasets
+
+SCRIPT_DIR = os.path.dirname(os.path.realpath(__file__))
+
+
+def main(args):
+    output_path = os.path.join(SCRIPT_DIR, args.output)
+    digits = datasets.load_digits()
+
+    rnd = 42
+    _, data, _, _ = train_test_split(digits.data, digits.target,
+                                     random_state=rnd)
+    data = data[args.index]
+    np.ndarray.tofile(data.astype('float32'), output_path)
+
+    if args.no_plot is False:
+        plt.gray()
+        plt.imshow(data.reshape(8, 8))
+        plt.show()
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-i", "--index", type=int, default=0,
+                        help="Image index in MNIST test dataset")
+    parser.add_argument("-o", "--output", type=str, default='digit',
+                        help="Output filename")
+    parser.add_argument("--no-plot", default=False, action='store_true',
+                        help="Disable image display in matplotlib")
+    main(parser.parse_args())

tests/pkg_emlearn/generate_model.py

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+#!/usr/bin/env python3
+
+import emlearn
+import joblib
+
+estimator = joblib.load("model")
+cmodel = emlearn.convert(estimator)
+cmodel.save(file='model.h')

tests/pkg_emlearn/main.c

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+/*
+ * Copyright (C) 2019 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Emlearn test application
+ *
+ * @author      Alexandre Abadie <alexandre.abadie@inria.fr>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+
+#include "model.h"
+
+/* the digit array included must be 4-byte aligned */
+__attribute__((__aligned__(4)))
+#include "blob/digit.h"
+
+int main(void)
+{
+    printf("Predicted digit: %" PRIi32 "\n",
+           model_predict((const float *)digit, digit_len >> 2));
+
+    return 0;
+}

tests/pkg_emlearn/tests/01-run.py

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+#!/usr/bin/env python3
+
+# Copyright (C) 2019 Inria
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+import sys
+from testrunner import run
+
+
+def testfunc(child):
+    child.expect_exact("Predicted digit: 6")
+
+
+if __name__ == "__main__":
+    sys.exit(run(testfunc))

tests/pkg_emlearn/train_model.py

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+#!/usr/bin/env python3
+
+import joblib
+
+from sklearn.model_selection import train_test_split
+from sklearn.ensemble import RandomForestClassifier
+from sklearn import metrics, datasets
+
+rnd = 42
+digits = datasets.load_digits()
+Xtrain, Xtest, ytrain, ytest = train_test_split(digits.data, digits.target, random_state=rnd)
+
+print('Loading digits dataset. 8x8=64 features')
+
+# 0.95+ with n_estimators=10, max_depth=10
+trees = 10
+max_depth = 10
+print('Training {} trees with max_depth {}'.format(trees, max_depth))
+model = RandomForestClassifier(n_estimators=trees, max_depth=max_depth, random_state=rnd)
+model.fit(Xtrain, ytrain)
+
+# Predict
+ypred = model.predict(Xtest)
+print('Accuracy on validation set {:.2f}%'.format(metrics.accuracy_score(ypred, ytest)*100))
+
+# Store the model in a binary file
+joblib.dump(model, "model")