Loading and inference in TensorFlow - ML Experiment: Train & Evaluate

Experiment - Loading and inference

Problem:You have a trained TensorFlow model saved on disk. You want to load this model and use it to make predictions on new data.

Current Metrics:No current metrics because the model is not yet loaded or used for inference.

Issue:Learners often struggle with correctly loading a saved model and running inference to get predictions.

Your Task

Load the saved TensorFlow model from disk and run inference on a given input sample. Output the predicted class probabilities.

Use TensorFlow 2.x API for loading and inference.

Do not retrain or modify the model architecture.

Input data must be preprocessed as required by the model.

Hint 1

Hint 2

Hint 3

Solution

TensorFlow

import tensorflow as tf
import numpy as np

# Load the saved model from disk
model = tf.keras.models.load_model('saved_model/my_model')

# Example input: a single sample with shape matching model input
# For example, if model expects 28x28 grayscale images:
input_sample = np.random.rand(1, 28, 28, 1).astype(np.float32)  # batch size 1

# Run inference
predictions = model.predict(input_sample)

# Print predicted class probabilities
print('Predicted probabilities:', predictions)

Loaded the saved model using tf.keras.models.load_model().

Created a dummy input sample with correct shape and type.

Used model.predict() to get output probabilities.

Results Interpretation

Before: No model loaded, no predictions possible.

After: Model loaded successfully and predictions generated as probability scores for each class.

Loading a saved TensorFlow model and running inference requires correct loading API, proper input shape, and using model.predict() to get output probabilities.

Bonus Experiment

Try loading the model and running inference on multiple input samples at once (batch inference).

💡 Hint

Prepare a batch input array with shape (batch_size, height, width, channels) and pass it to model.predict().

Practice

1. What is the main purpose of tf.keras.models.load_model() in TensorFlow?

easy

A. To visualize the model architecture

B. To load a previously saved model for inference or further training

C. To compile a model with loss and optimizer

D. To create a new model architecture from scratch

Solution

1. Step 1: Understand the function purpose

   tf.keras.models.load_model() is used to load a model that was saved earlier, including its architecture, weights, and optimizer state.

2. Step 2: Differentiate from other functions

   Creating a new model or compiling it are separate steps. Loading is specifically for retrieving a saved model.

3. Final Answer:

   To load a previously saved model for inference or further training -> Option B

4. Quick Check:

   Load saved model = load_model() [OK]

Hint: Load saved models with load_model() function [OK]

Common Mistakes:

• Confusing load_model() with model creation
• Thinking load_model() compiles the model
• Assuming load_model() only loads weights

2. Which of the following is the correct way to get predictions from a loaded TensorFlow model named model on input data new_data?

easy

A. predictions = model.predict(new_data)

B. predictions = model.fit(new_data)

C. predictions = model.evaluate(new_data)

D. predictions = model.compile(new_data)

Solution

1. Step 1: Identify the correct method for inference

   To get predictions from a model, the method predict() is used.

2. Step 2: Understand other methods

   fit() trains the model, evaluate() tests performance, and compile() sets up the model.

3. Final Answer:

   predictions = model.predict(new_data) -> Option A

4. Quick Check:

   Predict new data = model.predict() [OK]

Hint: Use model.predict() to get predictions [OK]

Common Mistakes:

• Using fit() instead of predict() for inference
• Calling evaluate() expecting predictions
• Trying to compile() during prediction

3. Given the following code, what will be the shape of predictions?

import tensorflow as tf
import numpy as np
model = tf.keras.Sequential([
  tf.keras.layers.Dense(3, input_shape=(4,))
])
model.compile(optimizer='adam', loss='mse')
input_data = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
predictions = model.predict(input_data)

medium

A. (3, 4)

B. (4, 3)

C. (2, 3)

D. (2, 4)

Solution

1. Step 1: Analyze input shape and batch size

   The input data has shape (2, 4) meaning 2 samples, each with 4 features.

2. Step 2: Determine output shape from model layer

   The Dense layer outputs 3 units per sample, so output shape is (2, 3).

3. Final Answer:

   (2, 3) -> Option C

4. Quick Check:

   Input batch 2, output units 3 = (2, 3) [OK]

Hint: Output shape = (batch_size, units in last layer) [OK]

Common Mistakes:

• Confusing input shape with output shape
• Mixing batch size and feature dimensions
• Assuming output shape matches input shape

4. You loaded a model with model = tf.keras.models.load_model('my_model') but get this error when calling model.predict(new_data): ValueError: Error when checking input: expected dense_input to have shape (4,) but got array with shape (3,). What is the likely cause?

medium

A. The input data shape does not match the model's expected input shape

B. The model was not compiled before prediction

C. The model file is corrupted

D. The predict() method was called without training the model

Solution

1. Step 1: Understand the error message

   The error says the model expects input shape (4,), but received (3,), meaning input data shape is wrong.

2. Step 2: Rule out other causes

   Model compilation is not required for prediction, corrupted files cause different errors, and training is not needed for predict().

3. Final Answer:

   The input data shape does not match the model's expected input shape -> Option A

4. Quick Check:

   Input shape mismatch = ValueError [OK]

Hint: Match input data shape to model input shape exactly [OK]

Common Mistakes:

• Ignoring input shape mismatch
• Thinking model must be compiled before predict
• Assuming predict requires training first

5. You have a saved TensorFlow model that expects input shape (None, 5). You want to predict on a single sample with 5 features stored in a list sample = [1, 2, 3, 4, 5]. Which code snippet correctly prepares the input and gets the prediction?

hard

A. input_data = np.array(sample)
prediction = model.predict(input_data)

B. input_data = np.array(sample).reshape(1, 1, 5)
prediction = model.predict(input_data)

C. input_data = np.array(sample).reshape(5, 1)
prediction = model.predict(input_data)

D. import numpy as np
input_data = np.array([sample])
prediction = model.predict(input_data)

Solution

1. Step 1: Understand model input shape

   The model expects input shape (None, 5), where None is batch size, so input must be 2D with shape (batch_size, 5).

2. Step 2: Prepare input data correctly

   Wrapping the sample list in another list creates shape (1, 5), which matches expected input.

3. Step 3: Check other options

   input_data = np.array(sample) prediction = model.predict(input_data) gives shape (5,), not 2D; input_data = np.array(sample).reshape(5, 1) prediction = model.predict(input_data) reshapes to (5,1) which is wrong; input_data = np.array(sample).reshape(1, 1, 5) prediction = model.predict(input_data) reshapes to (1,1,5) which is 3D and incorrect.

4. Final Answer:

   import numpy as np input_data = np.array([sample]) prediction = model.predict(input_data) -> Option D

5. Quick Check:

   Input shape (1,5) matches model input [OK]

Hint: Wrap single sample in list to add batch dimension [OK]

Common Mistakes:

• Passing 1D array instead of 2D batch input
• Incorrect reshaping causing wrong input dimensions
• Adding extra unnecessary dimensions