num_noise_spans should be <= num_items #22246 (#22938)

examples/flax/language-modeling/run_t5_mlm_flax.py

@@ -418,13 +418,14 @@ class FlaxDataCollatorForT5MLM:
         orig_length = length
 
         num_noise_tokens = int(np.round(length * self.noise_density))
+        num_nonnoise_tokens = length - num_noise_tokens
         # avoid degeneracy by ensuring positive numbers of noise and nonnoise tokens.
         num_noise_tokens = min(max(num_noise_tokens, 1), length - 1)
-        num_noise_spans = int(np.round(num_noise_tokens / self.mean_noise_span_length))
+        # num_noise_tokens should be less than num_noise_tokens and num_nonnoise_tokens
+        num_noise_spans = int(np.round(min(num_noise_tokens, num_nonnoise_tokens) / self.mean_noise_span_length))
 
         # avoid degeneracy by ensuring positive number of noise spans
         num_noise_spans = max(num_noise_spans, 1)
-        num_nonnoise_tokens = length - num_noise_tokens
 
         # pick the lengths of the noise spans and the non-noise spans
         def _random_segmentation(num_items, num_segments):