Evaluation

Automatic Evaluation with Pre-implemented Metrics
Welcome to the "Evaluation" tutorial of the "From Zero to Hero" series. In this part we will present the functionalities offered by the evaluation module.
!pip install git+https://github.com/ContinualAI/avalanche.git
📈 The Evaluation Module
The evaluation module is quite straightforward: it offers all the basic functionalities to evaluate and keep track of a continual learning experiment.
This is mostly done through the Metrics: a set of classes which implement the main continual learning metrics computation like Accuracy, Forgetting, Memory Usage, Running Times, etc. At the moment, in Avalanche we offer a number of pre-implemented metrics you can use for your own experiments. We made sure to include all the major accuracy-based metrics but also the ones related to computation and memory.
Each metric comes with a standalone class and a set of plugin classes aimed at emitting metric values on specific moments during training and evaluation.
Standalone metric
As an example, the standalone Accuracy class can be used to monitor the average accuracy over a stream of <input,target> pairs. The class provides an update method to update the current average accuracy, a result method to print the current average accuracy and a reset method to set the current average accuracy to zero. The call to resultdoes not change the metric state.
import torch
from avalanche.evaluation.metrics import Accuracy
​
# create an instance of the standalone Accuracy metric
# initial accuracy is 0
acc_metric = Accuracy()
print("Initial Accuracy: ", acc_metric.result()) #  output 0
​
# two consecutive metric updates
real_y = torch.tensor([1, 2]).long()
predicted_y = torch.tensor([1, 0]).float()
acc_metric.update(real_y, predicted_y)
acc = acc_metric.result()
print("Average Accuracy: ", acc) # output 0.5
predicted_y = torch.tensor([1,2]).float()
acc_metric.update(real_y, predicted_y)
acc = acc_metric.result()
print("Average Accuracy: ", acc) # output 0.75
​
# reset accuracy to 0
acc_metric.reset()
print("After reset: ", acc_metric.result()) # output 0
Plugin metric
If you want to integrate the available metrics automatically in the training and evaluation flow, you can use plugin metrics, like EpochAccuracy which logs the accuracy after each training epoch, or ExperienceAccuracy which logs the accuracy after each evaluation experience. Each of these metrics emits a curve composed by its values at different points in time (e.g. on different training epochs). In order to simplify the use of these metrics, we provided utility functions with which you can create different plugin metrics in one shot. The results of these functions can be passed as parameters directly to the EvaluationPlugin(see below).
We recommend to use the helper functions when creating plugin metrics.
from avalanche.evaluation.metrics import accuracy_metrics, \
    loss_metrics, forgetting_metrics, bwt_metrics,\
    confusion_matrix_metrics, cpu_usage_metrics, \
    disk_usage_metrics, gpu_usage_metrics, MAC_metrics, \
    ram_usage_metrics, timing_metrics
​
# you may pass the result to the EvaluationPlugin
metrics = accuracy_metrics(epoch=True, experience=True)
The metrics currently available in the current Avalanche release are:
from avalanche.evaluation.metrics import Accuracy, \
MinibatchAccuracy, EpochAccuracy, RunningEpochAccuracy, \
ExperienceAccuracy, StreamAccuracy, \
Loss, MinibatchLoss, EpochLoss, RunningEpochLoss, \
ExperienceLoss, StreamLoss, \
Forgetting, ExperienceForgetting, StreamForgetting, \
BWT, ExperienceBWT, StreamBWT, \
ConfusionMatrix, StreamConfusionMatrix, WandBStreamConfusionMatrix, \
CPUUsage, MinibatchCPUUsage, EpochCPUUsage, RunningEpochCPUUsage, \
ExperienceCPUUsage, StreamCPUUsage, \
DiskUsage, MinibatchDiskUsage, EpochDiskUsage, \
ExperienceDiskUsage, StreamDiskUsage, \
MaxGPU, MinibatchMaxGPU, EpochMaxGPU, ExperienceMaxGPU, \
StreamMaxGPU,\
MAC, MinibatchMAC, EpochMAC, ExperienceMAC, \
MaxRAM, MinibatchMaxRAM, EpochMaxRAM, ExperienceMaxRAM, \
StreamMaxRAM, \
ElapsedTime, MinibatchTime, EpochTime, RunningEpochTime, \
ExperienceTime, StreamTime
📐Evaluation Plugin
The Evaluation Plugin, is the object in charge of configuring and controlling the evaluation procedure. This object can be passed to a Strategy as a "special" plugin through the evaluator attribute.
The Evaluation Plugin accepts as inputs the plugin metrics you want to track. In addition, you can add one or more loggers to print the metrics in different ways (on file, on standard output, on Tensorboard...).
from torch.nn import CrossEntropyLoss
from torch.optim import SGD
from avalanche.benchmarks.classic import SplitMNIST
from avalanche.evaluation.metrics import forgetting_metrics, \
accuracy_metrics, loss_metrics, timing_metrics, cpu_usage_metrics, \
confusion_matrix_metrics, disk_usage_metrics
from avalanche.models import SimpleMLP
from avalanche.training.plugins import EvaluationPlugin
from avalanche.training.strategies import Naive
​
scenario = SplitMNIST(n_experiences=5)
​
# MODEL CREATION
model = SimpleMLP(num_classes=scenario.n_classes)
​
# DEFINE THE EVALUATION PLUGIN
# The evaluation plugin manages the metrics computation.
# It takes as argument a list of metrics, collectes their results and returns
# them to the strategy it is attached to.
​
eval_plugin = EvaluationPlugin(
    accuracy_metrics(minibatch=True, epoch=True, experience=True, stream=True),
    loss_metrics(minibatch=True, epoch=True, experience=True, stream=True),
    timing_metrics(epoch=True),
    forgetting_metrics(experience=True, stream=True),
    cpu_usage_metrics(experience=True),
    confusion_matrix_metrics(num_classes=scenario.n_classes, save_image=False, stream=True),
    disk_usage_metrics(minibatch=True, epoch=True, experience=True, stream=True)
)
​
# CREATE THE STRATEGY INSTANCE (NAIVE)
cl_strategy = Naive(
    model, SGD(model.parameters(), lr=0.001, momentum=0.9),
    CrossEntropyLoss(), train_mb_size=500, train_epochs=1, eval_mb_size=100,
    evaluator=eval_plugin)
​
# TRAINING LOOP
print('Starting experiment...')
results = []
for experience in scenario.train_stream:
    print("Start of experience: ", experience.current_experience)
    print("Current Classes: ", experience.classes_in_this_experience)
​
    # train returns a dictionary which contains all the metric values
    res = cl_strategy.train(experience)
    print('Training completed')
​
    print('Computing accuracy on the whole test set')
    # test also returns a dictionary which contains all the metric values
    results.append(cl_strategy.eval(scenario.test_stream))
Implement your own metric
To implement a standalone metric, you have to subclass Metric class.
from avalanche.evaluation import Metric
​
​
# a standalone metric implementation
class MyStandaloneMetric(Metric[float]):
    """
    This metric will return a `float` value
    """
    def __init__(self):
        """
        Initialize your metric here
        """
        super().__init__()
        pass
​
    def update(self):
        """
        Update metric value here
        """
        pass
​
    def result(self) -> float:
        """
        Emit the metric result here
        """
        return 0
​
    def reset(self):
        """
        Reset your metric here
        """
        pass
To implement a plugin metric you have to subclass MetricPlugin class
from avalanche.evaluation import PluginMetric
from avalanche.evaluation.metrics import Accuracy
​
​
class MyPluginMetric(PluginMetric[float]):
    """
    This metric will return a `float` value after
    each training epoch
    """
​
    def __init__(self):
        """
        Initialize the metric
        """
        super().__init__()
​
        self._accuracy_metric = Accuracy()
        # current x values for the metric curve
        self.x_coord = 0
​
    def reset(self) -> None:
        """
        Reset the metric
        """
        self._accuracy_metric.reset()
​
    def result(self) -> float:
        """
        Emit the result
        """
        return self._accuracy_metric.result()
​
    def after_training_iteration(self, strategy: 'PluggableStrategy') -> None:
        """
        Update the accuracy metric with the current
        predictions and targets
        """
        self._accuracy_metric.update(strategy.mb_y,
                                     strategy.logits)
​
    def before_training_epoch(self, strategy: 'PluggableStrategy') -> None:
        """
        Reset the accuracy before the epoch begins
        """
        self.reset()
​
    def after_training_epoch(self, strategy: 'PluggableStrategy'):
        """
        Emit the result
        """
        value = self._accuracy_metric.result()
        self.x_coord += 1 # increment x value
        return [MetricValue(self, 'metric_full_name', value,
                            self.x_coord)]
​
    def __str__(self):
        """
        Here you can specify the name of your metric
        """
        return "Top1_Acc_Epoch"
Accessing metric values
If you want to access all the metrics computed during training and evaluation, you have to make sure that collect_all=True is set when creating the EvaluationPlugin (default option is True). This option maintains an updated version of all metric results in the plugin, which can be retrieved by calling evaluation_plugin.get_all_metrics(). You can call this methods whenever you need the metrics.
The result is a dictionary with full metric names as keys and a tuple of two lists as values. The first list stores all the x values recorded for that metric. Each x value represents the time step at which the corresponding metric value has been computed. The second list stores metric values associated to the corresponding x value.
eval_plugin = EvaluationPlugin(
    accuracy_metrics(minibatch=True, epoch=True, experience=True, stream=True),
    loss_metrics(minibatch=True, epoch=True, experience=True, stream=True),
    forgetting_metrics(experience=True, stream=True),
    timing_metrics(epoch=True),
    cpu_usage_metrics(experience=True),
    confusion_matrix_metrics(num_classes=scenario.n_classes, save_image=False, stream=True),
    disk_usage_metrics(minibatch=True, epoch=True, experience=True, stream=True),
    collect_all=True # this is default value anyway
)
​
# since no training and evaluation has been performed, this will return an empty dict.
metric_dict = eval_plugin.get_all_metrics()
Alternatively, the train and eval method of every strategy returns a dictionary storing, for each metric, the last value recorded for that metric. You can use these dictionaries to incrementally accumulate metrics.
This completes the "Evaluation" tutorial for the "From Zero to Hero" series. We hope you enjoyed it!
🤝 Run it on Google Colab
You can run this chapter and play with it on Google Colaboratory: ​​​
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