def _fit_stage(self, X, y, rmTolerance):
"""
fits one stage of gradient boosting
@param X:
@param y:
@param rmTolerance: tolerance for 1D optimization
@return: nothing
"""
residuals = self.lossFunction.negative_gradient(y, self._currentPrediction)
trainX, trainY, _, _ = splitTrainTest(X, residuals, 1-self.subsample) # stochastic boosting. train only on a portion of the data
if len(np.unique(trainY))==1:
hm = MajorityPredictor().fit(trainY)
else:
cvObj = KFold(n=len(trainX), n_folds=self.cvNumFolds, indices=False, shuffle=True, random_state=self.randomState)
# find the h that best mimics the negative gradient
if self.n_jobs > 1: # parallel
n_jobs = max(1, self.n_jobs/len(self.learners), self.cvNumFolds)
# n_jobs = 1
pool = MyPool(processes=self.n_jobs, initializer=gbjjInit, initargs=(trainX, trainY, self.lossFunction, n_jobs, cvObj))
temp = pool.map_async(gbjjInnerLoop, self.learners)
temp.wait()
h_res = temp.get()
pool.close()
pool.join()
else: # single thread
h_res = []
for learner in self.learners:
if self.verbosity >= 2:
print 'Fitting learner:', learner
l = clone(learner)
scores = jjcross_val_score(l, trainX, trainY, score_func=self.lossFunction, n_jobs=1, cv=cvObj)
h_res.append(scores.mean())
hm = clone(self.learners[np.argsort(h_res)[0]])
if self.verbosity>=1:
print "The best classifier is", hm.__class__
# find rm
hm.fit(trainX, trainY)
hmx = hm.predict(X)
rm = minimize_scalar(lambda r: self.lossFunction(y, self._currentPrediction + r*hmx), tol=rmTolerance).x
# append estimator and weight
self._estimators.append((hm, rm))
def jjcross_val_score(clf, X, y, score_func, cv, y_test=None, n_jobs=cpu_count(), use_predProb_instead=False,
fit_params=None, weights=None, verbose=True):
"""
@param clf:
@param X: np.array
@param y: np.array
@param y_test: np.array. If not None then the Y's used for testing are different from the ones used for training.
@param score_func: a score function of the form func(y_true, y_pred)
@param cv: either an integer indicating the number of StratifiedKFold folds, or an iterable
@param n_jobs:
@param fit_params: parameters to pass to the estimator's fit method
@param socre_params: parameters to pass to score_func
@return: array of scores
"""
cv = check_cv(cv, X, y, classifier=is_classifier(clf))
# print 'cv:', cv
fit_params = fit_params if fit_params is not None else {}
# weights = weights if weights is not None else {}
if n_jobs > 1:
# figure out the number of folds
n_jobs = min(n_jobs, getNumCvFolds(cv))
# print 'jjcvscore with %d proceses' % n_jobs
pool = MyPool(n_jobs, initializer=jjcross_val_score_init,
initargs=(X, y, clf, score_func, fit_params, weights, y_test, use_predProb_instead))
data = [[trainInds, testInds] for trainInds, testInds in cv]
temp = pool.map_async(jjcross_val_score_inner, data)
temp.wait()
scores = temp.get()
pool.close()
pool.join()
else:
# print 'jjcvscore single thread'
scores = []
fold = 1
for trainInds, testInds in cv:
# print '=========== fold %d ===========' % fold
trainX = X[trainInds]
trainY = y[trainInds]
testX = X[testInds]
testY = (y if y_test is None else y_test)[testInds]
if weights is not None:
trainWeights = weights[trainInds]
testWeights = weights[testInds]
if len(np.unique(trainY))==1:
yPred = np.repeat(trainY[0], len(testY))
else:
clonedClf = clone(clf)
if weights is not None and 'sample_weight' in clonedClf.fit.func_code.co_varnames:
try:
clonedClf.fit(trainX, trainY, sample_weight=trainWeights, **fit_params)
except:
clonedClf.fit(trainX, trainY, **fit_params)
else:
clonedClf.fit(trainX, trainY, **fit_params)
yPred = clonedClf.predict_proba(testX)[:, 0] if use_predProb_instead else clonedClf.predict(testX)
if weights is None:
score = score_func(testY, yPred)
else:
score = score_func(testY, yPred, sample_weight=testWeights)
scores.append(score)
fold += 1
if verbose:
for i, score in enumerate(scores):
print 'Fold %d, score = %f' % (i, score)
print ">>>>>>>> %d-fold Score (mean, cv) = (%f, %f)" % (len(cv), np.mean(scores), np.std(scores)/np.mean(scores))
return np.array(scores)
