Answer: 2000

In 5-fold cross-validation, the dataset is divided into 5 parts, and the model is trained 5 times with each part serving as the validation set once. With 4 different parameter configurations, each configuration is trained 5 times, resulting in a total of 4 * 5 = 20 model trainings. Since each training involves a full run of the dataset, the total number of models trained is 20 * 1000 = 2000.

Author: LeetQuiz Editorial Team