cont : assert that sequence positions are not decreasing

ggml-ci

Author: ggerganov

src/llama-batch.cpp

@@ -282,7 +282,7 @@ bool llama_batch_allocr::init(
         }
     }
 
-    // disallow disjoint sequence sets:
+    // disallow partial sequence sub-sets:
     //
     // invalid:          x
     //            i: 0 1 2 ...
@@ -291,28 +291,46 @@ bool llama_batch_allocr::init(
     // seq_id[i][1]: 1 1 2
     // seq_id[i][2]: 2
     //
+    // disallow decreasing sequence positions:
+    //
+    // invalid:                  x
+    //            i: 0 1 2 3 4 5 6 ...
+    // ---------------------------------------
+    //       pos[i]: 4 5 0 1 6 2 3
+    // seq_id[i][0]: 0 0 1 1 0 1 0
+    //
     {
         seq_set_t cur_seq_set[LLAMA_MAX_SEQ];
         for (int32_t s = 0; s < LLAMA_MAX_SEQ; ++s) {
             cur_seq_set[s].set();
         }
 
+        llama_pos cur_seq_pos[LLAMA_MAX_SEQ];
+        for (int32_t s = 0; s < LLAMA_MAX_SEQ; ++s) {
+            cur_seq_pos[s] = -1;
+        }
+
         for (int32_t i = 0; i < batch.n_tokens; ++i) {
+            const llama_pos pos = batch.pos[i];
+
             for (int32_t s = 0; s < batch.n_seq_id[i]; ++s) {
                 const llama_seq_id seq_id = batch.seq_id[i][s];
 
                 cur_seq_set[seq_id] &= seq_set[i];
 
                 if (cur_seq_set[seq_id].none()) {
-                    LLAMA_LOG_ERROR("%s: sequence %d belongs to incompatible sequence sets\n", __func__, seq_id);
+                    LLAMA_LOG_ERROR("%s: sequence %d belongs to incompatible sequence sets (not allowed)\n", __func__, seq_id);
+                    return false;
+                }
+
+                if (pos < cur_seq_pos[seq_id]) {
+                    LLAMA_LOG_ERROR("%s: sequence %d positions are decreasing (not allowed)\n", __func__, seq_id);
                     return false;
                 }
             }
         }
     }
 
-    // TODO: check that positions are increasing
-
     split_reset();
 
     return true;