fix: add epsilon to prevent ZeroDivisionError in BPR-based models (#686)

The BPR zero-division fix (+ 1e-8) was previously applied to
recom_bpr.pyx but not to other models that use the same pattern:
- cornac/models/companion/recom_companion.pyx
- cornac/models/comparer/recom_comparer_sub.pyx
- cornac/models/lrppm/recom_lrppm.pyx

When all samples are skipped (e.g., on very small datasets),
the denominator (n_samples - skipped) becomes 0, causing a
ZeroDivisionError during training progress display.

Related to #675

Author: WeishuZ

cornac/models/companion/recom_companion.pyx

@@ -497,7 +497,7 @@ class Companion(Recommender):
                 progress.set_postfix({
                     "loss": "%.2f" % (loss / 3 / self.n_element_samples),
                     "bpr_loss": "%.2f" % (bpr_loss / self.n_bpr_samples),
-                    "correct": "%.2f%%" % (100.0 * correct / (self.n_bpr_samples - skipped)),
+                    "correct": "%.2f%%" % (100.0 * correct / (self.n_bpr_samples - skipped + 1e-8)),
                     "skipped": "%.2f%%" % (100.0 * skipped / self.n_bpr_samples),
                 })
 

cornac/models/comparer/recom_comparer_sub.pyx

@@ -472,7 +472,7 @@ class ComparERSub(MTER):
                 progress.set_postfix({
                     "loss": "%.2f" % (loss / 3 / self.n_element_samples),
                     "bpr_loss": "%.2f" % (bpr_loss / self.n_bpr_samples),
-                    "correct": "%.2f%%" % (100.0 * correct / (self.n_bpr_samples - skipped)),
+                    "correct": "%.2f%%" % (100.0 * correct / (self.n_bpr_samples - skipped + 1e-8)),
                     "skipped": "%.2f%%" % (100.0 * skipped / self.n_bpr_samples)
                 })
 

cornac/models/lrppm/recom_lrppm.pyx

@@ -331,7 +331,7 @@ class LRPPM(Recommender):
                     "loss": "%.2f" % (loss / self.n_samples),
                     "ranking_loss": "%.2f" % (ranking_loss / (self.n_ranking_samples - skipped)),
                     "r_loss": "%.2f" % (r_loss / (self.n_ranking_samples - skipped)),
-                    "correct": "%.2f%%" % (100.0 * correct / (self.n_ranking_samples - skipped)),
+                    "correct": "%.2f%%" % (100.0 * correct / (self.n_ranking_samples - skipped + 1e-8)),
                     "skipped": "%.2f%%" % (100.0 * skipped / self.n_ranking_samples)
                 })
                 if (