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Questa recensioni classifica notebook di film come positivo o negativo che utilizzano il testo della revisione. Questo è un esempio di binario -o due classi-classificazione, un tipo importante e ampiamente applicabile della macchina problema di apprendimento.
Useremo il set di dati IMDB che contiene il testo di 50.000 recensioni di film dalla Internet Movie Database . Questi sono suddivisi in 25.000 recensioni per la formazione e 25.000 recensioni per i test. I set di allenamento e test sono equilibrati, nel senso che contengono un uguale numero di recensioni positive e negative.
Questo notebook utilizza tf.keras , un'API di alto livello ai modelli costruire e formare in tensorflow, e tensorflow Hub , una biblioteca e una piattaforma per l'apprendimento di trasferimento. Per un testo più avanzato classificazione esercitazione usando tf.keras , vedere la MLCC Testo Classificazione Guida .
Più modelli
Qui si possono trovare modelli più espressivi o performanti che si potrebbe utilizzare per generare l'incorporamento testo.
Impostare
import numpy as np
import tensorflow as tf
import tensorflow_hub as hub
import tensorflow_datasets as tfds
import matplotlib.pyplot as plt
print("Version: ", tf.__version__)
print("Eager mode: ", tf.executing_eagerly())
print("Hub version: ", hub.__version__)
print("GPU is", "available" if tf.config.list_physical_devices('GPU') else "NOT AVAILABLE")
Version: 2.7.0 Eager mode: True Hub version: 0.12.0 GPU is available
Scarica il set di dati IMDB
Il dataset IMDB è disponibile sul set di dati tensorflow . Il codice seguente scarica il set di dati IMDB sul tuo computer (o il runtime colab):
train_data, test_data = tfds.load(name="imdb_reviews", split=["train", "test"],
batch_size=-1, as_supervised=True)
train_examples, train_labels = tfds.as_numpy(train_data)
test_examples, test_labels = tfds.as_numpy(test_data)
WARNING:tensorflow:From /tmpfs/src/tf_docs_env/lib/python3.7/site-packages/tensorflow_datasets/core/dataset_builder.py:622: get_single_element (from tensorflow.python.data.experimental.ops.get_single_element) is deprecated and will be removed in a future version. Instructions for updating: Use `tf.data.Dataset.get_single_element()`. WARNING:tensorflow:From /tmpfs/src/tf_docs_env/lib/python3.7/site-packages/tensorflow_datasets/core/dataset_builder.py:622: get_single_element (from tensorflow.python.data.experimental.ops.get_single_element) is deprecated and will be removed in a future version. Instructions for updating: Use `tf.data.Dataset.get_single_element()`.
Esplora i dati
Prendiamoci un momento per capire il formato dei dati. Ogni esempio è una frase che rappresenta la recensione del film e un'etichetta corrispondente. La sentenza non è in alcun modo preelaborata. L'etichetta è un valore intero di 0 o 1, dove 0 è una recensione negativa e 1 è una recensione positiva.
print("Training entries: {}, test entries: {}".format(len(train_examples), len(test_examples)))
Training entries: 25000, test entries: 25000
Stampiamo i primi 10 esempi.
train_examples[:10]
array([b"This was an absolutely terrible movie. Don't be lured in by Christopher Walken or Michael Ironside. Both are great actors, but this must simply be their worst role in history. Even their great acting could not redeem this movie's ridiculous storyline. This movie is an early nineties US propaganda piece. The most pathetic scenes were those when the Columbian rebels were making their cases for revolutions. Maria Conchita Alonso appeared phony, and her pseudo-love affair with Walken was nothing but a pathetic emotional plug in a movie that was devoid of any real meaning. I am disappointed that there are movies like this, ruining actor's like Christopher Walken's good name. I could barely sit through it.",
b'I have been known to fall asleep during films, but this is usually due to a combination of things including, really tired, being warm and comfortable on the sette and having just eaten a lot. However on this occasion I fell asleep because the film was rubbish. The plot development was constant. Constantly slow and boring. Things seemed to happen, but with no explanation of what was causing them or why. I admit, I may have missed part of the film, but i watched the majority of it and everything just seemed to happen of its own accord without any real concern for anything else. I cant recommend this film at all.',
b'Mann photographs the Alberta Rocky Mountains in a superb fashion, and Jimmy Stewart and Walter Brennan give enjoyable performances as they always seem to do. <br /><br />But come on Hollywood - a Mountie telling the people of Dawson City, Yukon to elect themselves a marshal (yes a marshal!) and to enforce the law themselves, then gunfighters battling it out on the streets for control of the town? <br /><br />Nothing even remotely resembling that happened on the Canadian side of the border during the Klondike gold rush. Mr. Mann and company appear to have mistaken Dawson City for Deadwood, the Canadian North for the American Wild West.<br /><br />Canadian viewers be prepared for a Reefer Madness type of enjoyable howl with this ludicrous plot, or, to shake your head in disgust.',
b'This is the kind of film for a snowy Sunday afternoon when the rest of the world can go ahead with its own business as you descend into a big arm-chair and mellow for a couple of hours. Wonderful performances from Cher and Nicolas Cage (as always) gently row the plot along. There are no rapids to cross, no dangerous waters, just a warm and witty paddle through New York life at its best. A family film in every sense and one that deserves the praise it received.',
b'As others have mentioned, all the women that go nude in this film are mostly absolutely gorgeous. The plot very ably shows the hypocrisy of the female libido. When men are around they want to be pursued, but when no "men" are around, they become the pursuers of a 14 year old boy. And the boy becomes a man really fast (we should all be so lucky at this age!). He then gets up the courage to pursue his true love.',
b"This is a film which should be seen by anybody interested in, effected by, or suffering from an eating disorder. It is an amazingly accurate and sensitive portrayal of bulimia in a teenage girl, its causes and its symptoms. The girl is played by one of the most brilliant young actresses working in cinema today, Alison Lohman, who was later so spectacular in 'Where the Truth Lies'. I would recommend that this film be shown in all schools, as you will never see a better on this subject. Alison Lohman is absolutely outstanding, and one marvels at her ability to convey the anguish of a girl suffering from this compulsive disorder. If barometers tell us the air pressure, Alison Lohman tells us the emotional pressure with the same degree of accuracy. Her emotional range is so precise, each scene could be measured microscopically for its gradations of trauma, on a scale of rising hysteria and desperation which reaches unbearable intensity. Mare Winningham is the perfect choice to play her mother, and does so with immense sympathy and a range of emotions just as finely tuned as Lohman's. Together, they make a pair of sensitive emotional oscillators vibrating in resonance with one another. This film is really an astonishing achievement, and director Katt Shea should be proud of it. The only reason for not seeing it is if you are not interested in people. But even if you like nature films best, this is after all animal behaviour at the sharp edge. Bulimia is an extreme version of how a tormented soul can destroy her own body in a frenzy of despair. And if we don't sympathise with people suffering from the depths of despair, then we are dead inside.",
b'Okay, you have:<br /><br />Penelope Keith as Miss Herringbone-Tweed, B.B.E. (Backbone of England.) She\'s killed off in the first scene - that\'s right, folks; this show has no backbone!<br /><br />Peter O\'Toole as Ol\' Colonel Cricket from The First War and now the emblazered Lord of the Manor.<br /><br />Joanna Lumley as the ensweatered Lady of the Manor, 20 years younger than the colonel and 20 years past her own prime but still glamourous (Brit spelling, not mine) enough to have a toy-boy on the side. It\'s alright, they have Col. Cricket\'s full knowledge and consent (they guy even comes \'round for Christmas!) Still, she\'s considerate of the colonel enough to have said toy-boy her own age (what a gal!)<br /><br />David McCallum as said toy-boy, equally as pointlessly glamourous as his squeeze. Pilcher couldn\'t come up with any cover for him within the story, so she gave him a hush-hush job at the Circus.<br /><br />and finally:<br /><br />Susan Hampshire as Miss Polonia Teacups, Venerable Headmistress of the Venerable Girls\' Boarding-School, serving tea in her office with a dash of deep, poignant advice for life in the outside world just before graduation. Her best bit of advice: "I\'ve only been to Nancherrow (the local Stately Home of England) once. I thought it was very beautiful but, somehow, not part of the real world." Well, we can\'t say they didn\'t warn us.<br /><br />Ah, Susan - time was, your character would have been running the whole show. They don\'t write \'em like that any more. Our loss, not yours.<br /><br />So - with a cast and setting like this, you have the re-makings of "Brideshead Revisited," right?<br /><br />Wrong! They took these 1-dimensional supporting roles because they paid so well. After all, acting is one of the oldest temp-jobs there is (YOU name another!)<br /><br />First warning sign: lots and lots of backlighting. They get around it by shooting outdoors - "hey, it\'s just the sunlight!"<br /><br />Second warning sign: Leading Lady cries a lot. When not crying, her eyes are moist. That\'s the law of romance novels: Leading Lady is "dewy-eyed."<br /><br />Henceforth, Leading Lady shall be known as L.L.<br /><br />Third warning sign: L.L. actually has stars in her eyes when she\'s in love. Still, I\'ll give Emily Mortimer an award just for having to act with that spotlight in her eyes (I wonder . did they use contacts?)<br /><br />And lastly, fourth warning sign: no on-screen female character is "Mrs." She\'s either "Miss" or "Lady."<br /><br />When all was said and done, I still couldn\'t tell you who was pursuing whom and why. I couldn\'t even tell you what was said and done.<br /><br />To sum up: they all live through World War II without anything happening to them at all.<br /><br />OK, at the end, L.L. finds she\'s lost her parents to the Japanese prison camps and baby sis comes home catatonic. Meanwhile (there\'s always a "meanwhile,") some young guy L.L. had a crush on (when, I don\'t know) comes home from some wartime tough spot and is found living on the street by Lady of the Manor (must be some street if SHE\'s going to find him there.) Both war casualties are whisked away to recover at Nancherrow (SOMEBODY has to be "whisked away" SOMEWHERE in these romance stories!)<br /><br />Great drama.',
b'The film is based on a genuine 1950s novel.<br /><br />Journalist Colin McInnes wrote a set of three "London novels": "Absolute Beginners", "City of Spades" and "Mr Love and Justice". I have read all three. The first two are excellent. The last, perhaps an experiment that did not come off. But McInnes\'s work is highly acclaimed; and rightly so. This musical is the novelist\'s ultimate nightmare - to see the fruits of one\'s mind being turned into a glitzy, badly-acted, soporific one-dimensional apology of a film that says it captures the spirit of 1950s London, and does nothing of the sort.<br /><br />Thank goodness Colin McInnes wasn\'t alive to witness it.',
b'I really love the sexy action and sci-fi films of the sixties and its because of the actress\'s that appeared in them. They found the sexiest women to be in these films and it didn\'t matter if they could act (Remember "Candy"?). The reason I was disappointed by this film was because it wasn\'t nostalgic enough. The story here has a European sci-fi film called "Dragonfly" being made and the director is fired. So the producers decide to let a young aspiring filmmaker (Jeremy Davies) to complete the picture. They\'re is one real beautiful woman in the film who plays Dragonfly but she\'s barely in it. Film is written and directed by Roman Coppola who uses some of his fathers exploits from his early days and puts it into the script. I wish the film could have been an homage to those early films. They could have lots of cameos by actors who appeared in them. There is one actor in this film who was popular from the sixties and its John Phillip Law (Barbarella). Gerard Depardieu, Giancarlo Giannini and Dean Stockwell appear as well. I guess I\'m going to have to continue waiting for a director to make a good homage to the films of the sixties. If any are reading this, "Make it as sexy as you can"! I\'ll be waiting!',
b'Sure, this one isn\'t really a blockbuster, nor does it target such a position. "Dieter" is the first name of a quite popular German musician, who is either loved or hated for his kind of acting and thats exactly what this movie is about. It is based on the autobiography "Dieter Bohlen" wrote a few years ago but isn\'t meant to be accurate on that. The movie is filled with some sexual offensive content (at least for American standard) which is either amusing (not for the other "actors" of course) or dumb - it depends on your individual kind of humor or on you being a "Bohlen"-Fan or not. Technically speaking there isn\'t much to criticize. Speaking of me I find this movie to be an OK-movie.'],
dtype=object)
Stampiamo anche le prime 10 etichette.
train_labels[:10]
array([0, 0, 0, 1, 1, 1, 0, 0, 0, 0])
Costruisci il modello
La rete neurale viene creata impilando i livelli: ciò richiede tre principali decisioni architetturali:
- Come rappresentare il testo?
- Quanti strati usare nel modello?
- Quante unità nascosti da utilizzare per ogni strato?
In questo esempio, i dati di input sono costituiti da frasi. Le etichette da prevedere sono 0 o 1.
Un modo per rappresentare il testo è convertire le frasi in vettori di incorporamenti. Possiamo utilizzare un incorporamento di testo pre-addestrato come primo livello, che avrà due vantaggi:
- non dobbiamo preoccuparci della preelaborazione del testo,
- possiamo trarre vantaggio dal trasferimento dell'apprendimento.
Per questo esempio useremo un modello da tensorflow Hub chiamato google / nnlm-en-dim50 / 2 .
Ci sono altri due modelli da testare per il bene di questo tutorial:
- google / nnlm-en-dim50-con-la normalizzazione / 2 - come google / nnlm-en-dim50 / 2 , ma con l'aggiunta di normalizzazione del testo per rimuovere la punteggiatura. Questo può aiutare a ottenere una migliore copertura degli incorporamenti nel vocabolario per i token nel testo di input.
- google / nnlm-en-dim128-con-la normalizzazione / 2 - Un modello più grande, con una dimensione l'incasso di 128 al posto del più piccolo 50.
Creiamo prima un livello Keras che utilizzi un modello TensorFlow Hub per incorporare le frasi e proviamolo su un paio di esempi di input. Si noti che la forma di uscita delle immersioni prodotte è previsto: (num_examples, embedding_dimension) .
model = "https://tfhub.dev/google/nnlm-en-dim50/2"
hub_layer = hub.KerasLayer(model, input_shape=[], dtype=tf.string, trainable=True)
hub_layer(train_examples[:3])
<tf.Tensor: shape=(3, 50), dtype=float32, numpy=
array([[ 0.5423194 , -0.01190171, 0.06337537, 0.0686297 , -0.16776839,
-0.10581177, 0.168653 , -0.04998823, -0.31148052, 0.07910344,
0.15442258, 0.01488661, 0.03930155, 0.19772716, -0.12215477,
-0.04120982, -0.27041087, -0.21922147, 0.26517656, -0.80739075,
0.25833526, -0.31004202, 0.2868321 , 0.19433866, -0.29036498,
0.0386285 , -0.78444123, -0.04793238, 0.41102988, -0.36388886,
-0.58034706, 0.30269453, 0.36308962, -0.15227163, -0.4439151 ,
0.19462997, 0.19528405, 0.05666233, 0.2890704 , -0.28468323,
-0.00531206, 0.0571938 , -0.3201319 , -0.04418665, -0.08550781,
-0.55847436, -0.2333639 , -0.20782956, -0.03543065, -0.17533456],
[ 0.56338924, -0.12339553, -0.10862677, 0.7753425 , -0.07667087,
-0.15752274, 0.01872334, -0.08169781, -0.3521876 , 0.46373403,
-0.08492758, 0.07166861, -0.00670818, 0.12686071, -0.19326551,
-0.5262643 , -0.32958236, 0.14394784, 0.09043556, -0.54175544,
0.02468163, -0.15456744, 0.68333143, 0.09068333, -0.45327246,
0.23180094, -0.8615696 , 0.3448039 , 0.12838459, -0.58759046,
-0.40712303, 0.23061076, 0.48426905, -0.2712814 , -0.5380918 ,
0.47016335, 0.2257274 , -0.00830665, 0.28462422, -0.30498496,
0.04400366, 0.25025868, 0.14867125, 0.4071703 , -0.15422425,
-0.06878027, -0.40825695, -0.31492147, 0.09283663, -0.20183429],
[ 0.7456156 , 0.21256858, 0.1440033 , 0.52338624, 0.11032254,
0.00902788, -0.36678016, -0.08938274, -0.24165548, 0.33384597,
-0.111946 , -0.01460045, -0.00716449, 0.19562715, 0.00685217,
-0.24886714, -0.42796353, 0.1862 , -0.05241097, -0.664625 ,
0.13449019, -0.22205493, 0.08633009, 0.43685383, 0.2972681 ,
0.36140728, -0.71968895, 0.05291242, -0.1431612 , -0.15733941,
-0.15056324, -0.05988007, -0.08178931, -0.15569413, -0.09303784,
-0.18971168, 0.0762079 , -0.02541647, -0.27134502, -0.3392682 ,
-0.10296471, -0.27275252, -0.34078008, 0.20083308, -0.26644838,
0.00655449, -0.05141485, -0.04261916, -0.4541363 , 0.20023566]],
dtype=float32)>
Costruiamo ora il modello completo:
model = tf.keras.Sequential()
model.add(hub_layer)
model.add(tf.keras.layers.Dense(16, activation='relu'))
model.add(tf.keras.layers.Dense(1))
model.summary()
Model: "sequential"
_________________________________________________________________
Layer (type) Output Shape Param #
=================================================================
keras_layer (KerasLayer) (None, 50) 48190600
dense (Dense) (None, 16) 816
dense_1 (Dense) (None, 1) 17
=================================================================
Total params: 48,191,433
Trainable params: 48,191,433
Non-trainable params: 0
_________________________________________________________________
I livelli sono impilati in sequenza per costruire il classificatore:
- Il primo livello è un livello TensorFlow Hub. Questo livello utilizza un modello salvato pre-addestrato per mappare una frase nel suo vettore di incorporamento. Il modello che stiamo utilizzando ( google / nnlm-en-dim50 / 2 ) divide la frase in token, incorpora ogni gettone e quindi unisce l'incorporamento. Le dimensioni risultanti sono:
(num_examples, embedding_dimension). - Questa uscita vettore a lunghezza fissa viene convogliata attraverso un (completamente collegato
Dense) strato con 16 unità nascoste. - L'ultimo strato è densamente connesso con un singolo nodo di output. Questo restituisce logits: le probabilità di log della vera classe, secondo il modello.
Unità nascoste
Il modello sopra ha due livelli intermedi o "nascosti", tra l'input e l'output. Il numero di output (unità, nodi o neuroni) è la dimensione dello spazio di rappresentazione per il livello. In altre parole, la quantità di libertà concessa alla rete nell'apprendere una rappresentazione interna.
Se un modello ha più unità nascoste (uno spazio di rappresentazione a più dimensioni) e/o più livelli, la rete può apprendere rappresentazioni più complesse. Tuttavia, rende la rete più costosa dal punto di vista computazionale e può portare all'apprendimento di modelli indesiderati, modelli che migliorano le prestazioni sui dati di addestramento ma non sui dati di test. Questo si chiama overfitting, e noi esploreremo in un secondo momento.
Funzione di perdita e ottimizzatore
Un modello necessita di una funzione di perdita e di un ottimizzatore per l'addestramento. Poiché questo è un problema di classificazione binaria e il modello uscite una probabilità (a strato singolo apparecchio con attivazione sigmoidale), useremo la binary_crossentropy funzione di perdita.
Questa non è l'unica scelta per una funzione di perdita, si potrebbe, per esempio, scegliere mean_squared_error . Ma, in generale, binary_crossentropy è migliore per trattare con le probabilità-misura la "distanza" tra distribuzioni di probabilità, o nel nostro caso, tra la distribuzione terra-verità e le previsioni.
In seguito, quando esploreremo problemi di regressione (ad esempio, per prevedere il prezzo di una casa), vedremo come utilizzare un'altra funzione di perdita chiamata errore quadratico medio.
Ora, configura il modello per utilizzare un ottimizzatore e una funzione di perdita:
model.compile(optimizer='adam',
loss=tf.losses.BinaryCrossentropy(from_logits=True),
metrics=[tf.metrics.BinaryAccuracy(threshold=0.0, name='accuracy')])
Crea un set di convalida
Durante l'addestramento, vogliamo verificare l'accuratezza del modello su dati che non ha mai visto prima. Creare un set di validazione impostando oltre 10.000 esempi dai dati formazione originale. (Perché non utilizzare il set di test ora? Il nostro obiettivo è sviluppare e ottimizzare il nostro modello utilizzando solo i dati di addestramento, quindi utilizzare i dati di test solo una volta per valutare la nostra precisione).
x_val = train_examples[:10000]
partial_x_train = train_examples[10000:]
y_val = train_labels[:10000]
partial_y_train = train_labels[10000:]
Allena il modello
Addestra il modello per 40 epoche in mini-lotti di 512 campioni. Si tratta di 40 iterazioni oltre tutti i campioni del x_train e y_train tensori. Durante l'addestramento, monitorare la perdita e l'accuratezza del modello sui 10.000 campioni del set di convalida:
history = model.fit(partial_x_train,
partial_y_train,
epochs=40,
batch_size=512,
validation_data=(x_val, y_val),
verbose=1)
Epoch 1/40 30/30 [==============================] - 2s 34ms/step - loss: 0.6667 - accuracy: 0.6060 - val_loss: 0.6192 - val_accuracy: 0.7195 Epoch 2/40 30/30 [==============================] - 1s 28ms/step - loss: 0.5609 - accuracy: 0.7770 - val_loss: 0.5155 - val_accuracy: 0.7882 Epoch 3/40 30/30 [==============================] - 1s 29ms/step - loss: 0.4309 - accuracy: 0.8489 - val_loss: 0.4135 - val_accuracy: 0.8364 Epoch 4/40 30/30 [==============================] - 1s 28ms/step - loss: 0.3154 - accuracy: 0.8937 - val_loss: 0.3515 - val_accuracy: 0.8583 Epoch 5/40 30/30 [==============================] - 1s 29ms/step - loss: 0.2345 - accuracy: 0.9227 - val_loss: 0.3256 - val_accuracy: 0.8639 Epoch 6/40 30/30 [==============================] - 1s 28ms/step - loss: 0.1773 - accuracy: 0.9457 - val_loss: 0.3104 - val_accuracy: 0.8702 Epoch 7/40 30/30 [==============================] - 1s 29ms/step - loss: 0.1331 - accuracy: 0.9645 - val_loss: 0.3024 - val_accuracy: 0.8741 Epoch 8/40 30/30 [==============================] - 1s 28ms/step - loss: 0.0984 - accuracy: 0.9777 - val_loss: 0.3061 - val_accuracy: 0.8758 Epoch 9/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0707 - accuracy: 0.9869 - val_loss: 0.3136 - val_accuracy: 0.8745 Epoch 10/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0501 - accuracy: 0.9919 - val_loss: 0.3305 - val_accuracy: 0.8743 Epoch 11/40 30/30 [==============================] - 1s 28ms/step - loss: 0.0351 - accuracy: 0.9960 - val_loss: 0.3434 - val_accuracy: 0.8726 Epoch 12/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0247 - accuracy: 0.9984 - val_loss: 0.3568 - val_accuracy: 0.8722 Epoch 13/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0178 - accuracy: 0.9993 - val_loss: 0.3711 - val_accuracy: 0.8700 Epoch 14/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0134 - accuracy: 0.9996 - val_loss: 0.3839 - val_accuracy: 0.8711 Epoch 15/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0103 - accuracy: 0.9998 - val_loss: 0.3968 - val_accuracy: 0.8701 Epoch 16/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0080 - accuracy: 0.9998 - val_loss: 0.4104 - val_accuracy: 0.8702 Epoch 17/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0063 - accuracy: 0.9999 - val_loss: 0.4199 - val_accuracy: 0.8694 Epoch 18/40 30/30 [==============================] - 1s 28ms/step - loss: 0.0051 - accuracy: 1.0000 - val_loss: 0.4305 - val_accuracy: 0.8691 Epoch 19/40 30/30 [==============================] - 1s 28ms/step - loss: 0.0043 - accuracy: 1.0000 - val_loss: 0.4403 - val_accuracy: 0.8688 Epoch 20/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0036 - accuracy: 1.0000 - val_loss: 0.4493 - val_accuracy: 0.8687 Epoch 21/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0031 - accuracy: 1.0000 - val_loss: 0.4580 - val_accuracy: 0.8682 Epoch 22/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0027 - accuracy: 1.0000 - val_loss: 0.4659 - val_accuracy: 0.8682 Epoch 23/40 30/30 [==============================] - 1s 31ms/step - loss: 0.0023 - accuracy: 1.0000 - val_loss: 0.4743 - val_accuracy: 0.8680 Epoch 24/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0020 - accuracy: 1.0000 - val_loss: 0.4808 - val_accuracy: 0.8678 Epoch 25/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0018 - accuracy: 1.0000 - val_loss: 0.4879 - val_accuracy: 0.8669 Epoch 26/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0016 - accuracy: 1.0000 - val_loss: 0.4943 - val_accuracy: 0.8667 Epoch 27/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0015 - accuracy: 1.0000 - val_loss: 0.5003 - val_accuracy: 0.8672 Epoch 28/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0013 - accuracy: 1.0000 - val_loss: 0.5064 - val_accuracy: 0.8665 Epoch 29/40 30/30 [==============================] - 1s 29ms/step - loss: 0.0012 - accuracy: 1.0000 - val_loss: 0.5120 - val_accuracy: 0.8668 Epoch 30/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0011 - accuracy: 1.0000 - val_loss: 0.5174 - val_accuracy: 0.8671 Epoch 31/40 30/30 [==============================] - 1s 30ms/step - loss: 0.0010 - accuracy: 1.0000 - val_loss: 0.5230 - val_accuracy: 0.8664 Epoch 32/40 30/30 [==============================] - 1s 29ms/step - loss: 9.2117e-04 - accuracy: 1.0000 - val_loss: 0.5281 - val_accuracy: 0.8663 Epoch 33/40 30/30 [==============================] - 1s 29ms/step - loss: 8.4693e-04 - accuracy: 1.0000 - val_loss: 0.5332 - val_accuracy: 0.8659 Epoch 34/40 30/30 [==============================] - 1s 30ms/step - loss: 7.8501e-04 - accuracy: 1.0000 - val_loss: 0.5376 - val_accuracy: 0.8666 Epoch 35/40 30/30 [==============================] - 1s 29ms/step - loss: 7.2613e-04 - accuracy: 1.0000 - val_loss: 0.5424 - val_accuracy: 0.8657 Epoch 36/40 30/30 [==============================] - 1s 29ms/step - loss: 6.7541e-04 - accuracy: 1.0000 - val_loss: 0.5468 - val_accuracy: 0.8659 Epoch 37/40 30/30 [==============================] - 1s 29ms/step - loss: 6.2841e-04 - accuracy: 1.0000 - val_loss: 0.5510 - val_accuracy: 0.8658 Epoch 38/40 30/30 [==============================] - 1s 29ms/step - loss: 5.8661e-04 - accuracy: 1.0000 - val_loss: 0.5553 - val_accuracy: 0.8656 Epoch 39/40 30/30 [==============================] - 1s 29ms/step - loss: 5.4869e-04 - accuracy: 1.0000 - val_loss: 0.5595 - val_accuracy: 0.8658 Epoch 40/40 30/30 [==============================] - 1s 30ms/step - loss: 5.1370e-04 - accuracy: 1.0000 - val_loss: 0.5635 - val_accuracy: 0.8659
Valuta il modello
E vediamo come si comporta il modello. Verranno restituiti due valori. Perdita (un numero che rappresenta il nostro errore, valori più bassi sono migliori) e precisione.
results = model.evaluate(test_examples, test_labels)
print(results)
782/782 [==============================] - 2s 3ms/step - loss: 0.6272 - accuracy: 0.8484 [0.6272369027137756, 0.848360002040863]
Questo approccio abbastanza ingenuo raggiunge una precisione di circa l'87%. Con approcci più avanzati, il modello dovrebbe avvicinarsi al 95%.
Crea un grafico di precisione e perdita nel tempo
model.fit() restituisce uno History oggetto che contiene un dizionario con tutto ciò che è accaduto durante l'allenamento:
history_dict = history.history
history_dict.keys()
dict_keys(['loss', 'accuracy', 'val_loss', 'val_accuracy'])
Sono disponibili quattro voci: una per ciascuna metrica monitorata durante l'addestramento e la convalida. Possiamo usarli per tracciare la perdita di addestramento e convalida per il confronto, nonché l'accuratezza di addestramento e convalida:
acc = history_dict['accuracy']
val_acc = history_dict['val_accuracy']
loss = history_dict['loss']
val_loss = history_dict['val_loss']
epochs = range(1, len(acc) + 1)
# "bo" is for "blue dot"
plt.plot(epochs, loss, 'bo', label='Training loss')
# b is for "solid blue line"
plt.plot(epochs, val_loss, 'b', label='Validation loss')
plt.title('Training and validation loss')
plt.xlabel('Epochs')
plt.ylabel('Loss')
plt.legend()
plt.show()
plt.clf() # clear figure
plt.plot(epochs, acc, 'bo', label='Training acc')
plt.plot(epochs, val_acc, 'b', label='Validation acc')
plt.title('Training and validation accuracy')
plt.xlabel('Epochs')
plt.ylabel('Accuracy')
plt.legend()
plt.show()
In questo grafico, i punti rappresentano la perdita di addestramento e l'accuratezza e le linee continue sono la perdita di convalida e l'accuratezza.
Si noti la perdita di formazione diminuisce con ogni epoca e la formazione di precisione aumenta con ogni epoca. Ciò è previsto quando si utilizza un'ottimizzazione della discesa del gradiente: dovrebbe ridurre al minimo la quantità desiderata ad ogni iterazione.
Questo non è il caso della perdita di convalida e dell'accuratezza: sembrano raggiungere il picco dopo una ventina di epoche. Questo è un esempio di overfitting: il modello ha prestazioni migliori sui dati di training rispetto a dati che non ha mai visto prima. Dopo questo punto, il modello over-ottimizza e impara rappresentazioni specifiche per i dati di allenamento che non generalizzano a dati di test.
Per questo caso particolare, potremmo prevenire il sovradattamento semplicemente interrompendo l'addestramento dopo una ventina di epoche. Successivamente, vedrai come farlo automaticamente con una richiamata.
# MIT License
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# Copyright (c) 2017 François Chollet
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