descriptions/description_parameter_grid.md

We define a grid of hyperparameters to be explored by the RandomizedSearchCV. Using a GridSearchCV instead would explore all the possible combinations on the grid, which can be costly to compute, whereas the parameter n_iter of the RandomizedSearchCV controls the number of different random combination that are evaluated. Notice that setting n_iter larger than the number of possible combinations in a grid would lead to repeating already-explored combinations. We search for the best parameter combination for both the feature extraction (vect__) and the classifier (clf__).