Commit 756ca10e authored by Carsten Eie Frigaard's avatar Carsten Eie Frigaard
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%% Cell type:markdown id: tags:
# ITMAL Exercise
## Hyperparameters and Gridsearch
When instantiating a Scikit-learn model in python most or all constructor parameters have _default_ values. These values are not part of the internal model and are hence called ___hyperparameters___---in contrast to _normal_ model parameters, for example the neuron weights, $\mathbf w$, for an `MLP` model.
### Manual Tuning Hyperparameters
Below is an example of the python constructor for the support-vector classifier `sklearn.svm.SVC`, with say the `kernel` hyperparameter having the default value `'rbf'`. If you should choose, what would you set it to other than `'rbf'`?
class sklearn.svm.SVC(
The default values might be a sensible general starting point, but for your data, you might want to optimize the hyperparameters to yield a better result.
To be able to set `kernel` to a sensible value you need to go into the documentation for the `SVC` and understand what the kernel parameter represents, and what values it can be set to, and you need to understand the consequences of setting `kernel` to something different than the default...and the story repeats for every other hyperparameter!
### Brute Force Search
An alternative to this structured, but time-consuming approach, is just to __brute-force__ a search of interesting hyperparameters, and choose the 'best' parameters according to a fit-predict and some score, say 'f1'.
<img src="" alt="WARNING: you need to be logged into Blackboard to view images" style="width:350px">
<center> Conceptual graphical view of grid search for two distinct hyperparameters. </center>
<center> Notice that you would normally search hyperparameters like `alpha` with an exponential range, say [0.01, 0.1, 1, 10] or similar.</center>
Now, you just pick out some hyperparameters, that you figure are important, set them to a suitable range, say
'kernel':('linear', 'rbf'),
'C':[1, 10]
and fire up a full (grid) search on this hyperparameter set, that will try out all your specified combination of `kernel` and `C` for the model, and then prints the hyperparameter set with the highest score...
The demo code below sets up some of our well known 'hello-world' data and then run a _grid search_ on a particular model, here a _support-vector classifier_ (SVC)
Other models and datasets ('mnist', 'iris', 'moon') can also be examined.
### Qa Explain GridSearchCV
There are two code cells below: 1) function setup, 2) the actual grid-search.
Review the code cells and write a __short__ summary. Mainly focus on __cell 2__, but dig into cell 1 if you find it interesting (notice the use of local-function, a nifty feature in python).
In detail, examine the lines:
grid_tuned = GridSearchCV(model, tuning_parameters, .., y_train)
FullReport(grid_tuned , X_test, y_test, time_gridsearch)
and write a short description of how the `GridSeachCV` works: explain how the search parameter set is created and the overall search mechanism is functioning (without going into too much detail).
What role does the parameter `scoring='f1_micro'` play in the `GridSearchCV`, and what does `n_jobs=-1` mean?
%% Cell type:code id: tags:
``` python
# TODO: Qa, code review..cell 1) function setup
from time import time
import numpy as np
from sklearn import svm
from sklearn.linear_model import SGDClassifier
from sklearn.model_selection import GridSearchCV, RandomizedSearchCV, train_test_split
from sklearn.metrics import classification_report, f1_score
from sklearn import datasets
from libitmal import dataloaders as itmaldataloaders # Needed for load of iris, moon and mnist
currmode="N/A" # GLOBAL var!
def SearchReport(model):
def GetBestModelCTOR(model, best_params):
def GetParams(best_params):
for key in sorted(best_params):
value = best_params[key]
temp_str = "'" if str(type(value))=="<class 'str'>" else ""
if len(ret_str)>0:
ret_str += ','
ret_str += f'{key}={temp_str}{value}{temp_str}'
return ret_str
param_str = GetParams(best_params)
return type(model).__name__ + '(' + param_str + ')'
return "N/A(1)"
print("\nBest model set found on train set:")
print(f"\tbest parameters={model.best_params_}")
print(f"\tbest '{model.scoring}' score={model.best_score_}")
print(f"\tbest index={model.best_index_}")
print(f"Best estimator CTOR:")
print(f"Grid scores ('{model.scoring}') on development set:")
means = model.cv_results_['mean_test_score']
stds = model.cv_results_['std_test_score']
for mean, std, params in zip(means, stds, model.cv_results_['params']):
print("\t[%2d]: %0.3f (+/-%0.03f) for %r" % (i, mean, std * 2, params))
i += 1
print("WARNING: the random search do not provide means/stds")
global currmode
assert "f1_micro"==str(model.scoring), f"come on, we need to fix the scoring to be able to compare model-fits! Your scoreing={str(model.scoring)}...remember to add scoring='f1_micro' to the search"
return f"best: dat={currmode}, score={model.best_score_:0.5f}, model={GetBestModelCTOR(model.estimator,model.best_params_)}", model.best_estimator_
def ClassificationReport(model, X_test, y_test, target_names=None):
assert X_test.shape[0]==y_test.shape[0]
print("\nDetailed classification report:")
print("\tThe model is trained on the full development set.")
print("\tThe scores are computed on the full evaluation set.")
y_true, y_pred = y_test, model.predict(X_test)
print(classification_report(y_true, y_pred, target_names))
def FullReport(model, X_test, y_test, t):
print(f"SEARCH TIME: {t:0.2f} sec")
beststr, bestmodel = SearchReport(model)
ClassificationReport(model, X_test, y_test)
print(f"CTOR for best model: {bestmodel}\n")
return beststr, bestmodel
def LoadAndSetupData(mode, test_size=0.3):
assert test_size>=0.0 and test_size<=1.0
def ShapeToString(Z):
n = Z.ndim
s = "("
for i in range(n):
s += f"{Z.shape[i]:5d}"
if i+1!=n:
s += ";"
return s+")"
global currmode
print(f"DATA: {currmode}..")
if mode=='moon':
X, y = itmaldataloaders.MOON_GetDataSet(n_samples=5000, noise=0.2)
itmaldataloaders.MOON_Plot(X, y)
elif mode=='mnist':
X, y = itmaldataloaders.MNIST_GetDataSet(load_mode=0)
if X.ndim==3:
X=np.reshape(X, (X.shape[0], -1))
elif mode=='iris':
X, y = itmaldataloaders.IRIS_GetDataSet()
raise ValueError(f"could not load data for that particular mode='{mode}', only 'moon'/'mnist'/'iris' supported")
print(f' org. data: X.shape ={ShapeToString(X)}, y.shape ={ShapeToString(y)}')
assert X.ndim==2
assert X.shape[0]==y.shape[0]
assert y.ndim==1 or (y.ndim==2 and y.shape[1]==0)
X_train, X_test, y_train, y_test = train_test_split(
X, y, test_size=test_size, random_state=0, shuffle=True
print(f' train data: X_train.shape={ShapeToString(X_train)}, y_train.shape={ShapeToString(y_train)}')
print(f' test data: X_test.shape ={ShapeToString(X_test)}, y_test.shape ={ShapeToString(y_test)}')
return X_train, X_test, y_train, y_test
print('OK(function setup, hope MNIST loads works, seem best if you got Keras or Tensorflow installed!)')
%% Cell type:code id: tags:
``` python
# TODO: Qa, code review..cell 2) the actual grid-search
# Setup data
X_train, X_test, y_train, y_test = LoadAndSetupData(
'iris') # 'iris', 'moon', or 'mnist'
# Setup search parameters
model = svm.SVC(
) # NOTE: gamma="scale" does not work in older Scikit-learn frameworks,
# FIX: replace with model = svm.SVC(gamma=0.001)
tuning_parameters = {
'kernel': ('linear', 'rbf'),
'C': [0.1, 1, 10]
CV = 5
# Run GridSearchCV for the model
start = time()
grid_tuned = GridSearchCV(model,
n_jobs=-1), y_train)
t = time() - start
# Report result
b0, m0 = FullReport(grid_tuned, X_test, y_test, t)
%% Cell type:markdown id: tags:
### Qb Hyperparameter Grid Search using an SDG classifier
Now, replace the `svm.SVC` model with an `SGDClassifier` and a suitable set of the hyperparameters for that model.
You need at least four or five different hyperparameters from the `SGDClassifier` in the search-space before it begins to take considerable compute time doing the full grid search.
So, repeat the search with the `SGDClassifier`, and be sure to add enough hyperparameters to the grid-search, such that the search takes a considerable time to run, that is a couple of minutes or up to some hours..
%% Cell type:code id: tags:
``` python
# TODO: grid search
assert False, "TODO: make a grid search on the SDG classifier.."
%% Cell type:markdown id: tags:
### Qc Hyperparameter Random Search using an SDG classifier
Now, add code to run a `RandomizedSearchCV` instead.
<img src="" alt="WARNING: you need to be logged into Blackboard to view images" style="width:350px" >
<center> Conceptual graphical view of randomized search for two distinct hyperparameters. </center>
Use these default parameters for the random search, similar to the default parameters for the grid search
random_tuned = RandomizedSearchCV(
but with the two new parameters, `n_iter` and `random_state` added. Since the search-type is now random, the `random_state` gives sense, but essential to random search is the new `n_tier` parameter.
So: investigate the `n_iter` code and write a conceptual explanation in text.
Comparison of time (seconds) to complete `GridSearch` versus `RandomizedSearchCV`, does not necessarily give any sense, if your grid search completes in a few seconds (as for the iris tiny-data). You need a search that runs for minutes, hours, or days.
But you could compare the best-tuned parameter set and best scoring for the two methods. Is the random search best model close to the grid search?
%% Cell type:code id: tags:
``` python
assert False, "implement a random search for the SGD classifier.."
%% Cell type:markdown id: tags:
## Qd MNIST Search Quest II
Finally, a search-quest competition: __who can find the best model+hyperparameters for the MNIST dataset?__
You change to the MNIST data by calling `LoadAndSetupData('mnist')`, and this is a completely other ball-game that the iris _tiny-data_: it's much larger (but still far from _big-data_)!
* You might opt for the exhaustive grid search, or use the faster but-less optimal random search...your choice.
* You are free to pick any classifier in Scikit-learn, even algorithms we have not discussed yet---__except Neural Networks and KNeighborsClassifier!__.
* Keep the score function at `f1_micro`, otherwise, we will be comparing 'æbler og pærer'.
* And, you may also want to scale your input data for some models to perform better.
* __REMEMBER__, DO NOT USE any Neural Network models. This also means not to use any `Keras` or `Tensorflow` models...since they outperform most other models, and there are also too many examples on the internet to cut-and-paste from!
Check your result by printing the first _return_ value from `FullReport()`
b1, m1 = FullReport(random_tuned , X_test, y_test, time_randomsearch)
that will display a result like
best: dat=mnist, score=0.90780, model=SGDClassifier(alpha=1.0,eta0=0.0001,learning_rate='invscaling')
and paste your currently best model into the message box, for ITMAL group 09 like
Grp09: best: dat=mnist, score=0.90780, model=SGDClassifier(alpha=1.0,eta0=0.0001,learning_rate='invscaling')
Grp09: CTOR for best model: SGDClassifier(alpha=1.0, average=False, class_weight=None, early_stopping=False,
epsilon=0.1, eta0=0.0001, fit_intercept=True, l1_ratio=0.15,
learning_rate='invscaling', loss='hinge', max_iter=1000,
n_iter_no_change=5, n_jobs=None, penalty='l2', power_t=0.5,
random_state=None, shuffle=True, tol=0.001,
validation_fraction=0.1, verbose=0, warm_start=False)
on Brightspace: "L10: Regularisering, optimering og søgning" | "Qd MNIST Search Quest II"
and, check if your score (for MNIST) is better than the currently best score. Republish if you get a better score than your own previously best.
Remember to provide an ITMAL group name manually, so we can identify a winner: the 1. st price is cake!
For the journal hand-in, report your progress in scoring choosing different models, hyperparameters to search and how you might need to preprocess your data...and note, that the journal will not be accepted unless it contains information about Your results published on the Brightspace 'Search Quest II' page!
%% Cell type:code id: tags:
``` python
# TODO:(in code and text..)
assert False, "participate in the Search Quest---remember to publish your result(s) on Brightspace."
%% Cell type:markdown id: tags:
---------| |
2018-0301| CEF, initial.
2018-0305| CEF, updated.
2018-0306| CEF, updated and spell checked.
2018-0306| CEF, major overhaul of functions.
2018-0306| CEF, fixed problem with MNIST load and Keras.
2018-0307| CEF, modified report functions and changed Qc+d.
2018-0311| CEF, updated Qd.
2018-0312| CEF, added grid and random search figs and added bullets to Qd.
2018-0313| CEF, fixed SVC and gamma issue, and changed dataload to be in fetchmode (non-keras).
2019-1015| CEF, updated for ITMAL E19
2019-1019| CEF, minor text update.
2019-1023| CEF, changed demo model i Qd) from MLPClassifier to SVC.
2020-0314| CEF, updated to ITMAL F20.
2020-1020| CEF, updated to ITMAL E20.
2020-1027| CEF, type fixes and minor update.
2020-1028| CEF, added extra journal hand-in specs for Search Quest II, Qd.
2020-1030| CEF, added non-use of KNeighborsClassifier to Search Quest II, Qd.
2020-1119| CEF, changed load_mode=2 (Keras) to load_mode=0 (auto) for MNIST loader.
2020-0317| CEF, updated to ITMAL F21.
2020-1031| CEF, updated to ITMAL E21.
2021-0317| CEF, updated to ITMAL F21.
2021-1031| CEF, updated to ITMAL E21.
2021-1105| CEF, removed iid=True paramter from GridSearchCV(), not present in current version of Scikit-learn (0.24.1).
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