sampling : cleanup and clarify output_reserve

Author: danbev

src/llama-context.cpp

@@ -1723,40 +1723,41 @@ uint32_t llama_context::output_reserve(int32_t n_outputs) {
         logits = has_logits ? output_base : nullptr;
         embd   = has_embd   ? output_base + logits_size : nullptr;
     } else {
+        // Allocate worst case (full vocabulary size) for backend sampled
+        // data in the pinned memory buffer.
         size_t offset = 0;
         uint8_t * base = (uint8_t *) output_base;
 
-        if (sampling.logits_size > 0) {
-            sampling.logits = (float *) (base + offset);
-            offset += sampling.logits_size * sizeof(float);
-        }
-        if (sampling.probs_size > 0) {
-            sampling.probs = (float *) (base + offset);
-            offset += sampling.probs_size * sizeof(float);
-        }
-        if (sampling.sampled_size > 0) {
-            sampling.sampled = (llama_token *) (base + offset);
-            offset += sampling.sampled_size * sizeof(llama_token);
-        }
-        if (sampling.candidates_size > 0) {
-            sampling.candidates = (llama_token *) (base + offset);
-            offset += sampling.candidates_size * sizeof(llama_token);
-        }
+        sampling.logits = (float *) (base + offset);
+        offset += sampling.logits_size * sizeof(float);
+
+        sampling.probs = (float *) (base + offset);
+        offset += sampling.probs_size * sizeof(float);
 
+        sampling.sampled = (llama_token *) (base + offset);
+        offset += sampling.sampled_size * sizeof(llama_token);
+
+        sampling.candidates = (llama_token *) (base + offset);
+        offset += sampling.candidates_size * sizeof(llama_token);
+
+        // The count vectors keep track of the actual number of logits/probs/candidates
+        // copied from the backend for each output row.
         const size_t n_rows = (size_t) n_outputs_max;
         if (sampling.outputs_capacity < n_rows) {
+            // The output size has increased, so resize and reset the count vectors.
             sampling.outputs_capacity = n_rows;
 
             sampling.logits_count.assign(n_rows, 0);
             sampling.probs_count.assign(n_rows, 0);
             sampling.candidates_count.assign(n_rows, 0);
         } else {
+            // The output size has not increased so just reset the counts to zero.
             std::fill(sampling.logits_count.begin(), sampling.logits_count.end(), 0);
             std::fill(sampling.probs_count.begin(),  sampling.probs_count.end(),  0);
             std::fill(sampling.candidates_count.begin(), sampling.candidates_count.end(), 0);
         }
 
-        if (sampling.sampled && sampling.sampled_size > 0) {
+        if (sampling.sampled) {
             std::fill_n(sampling.sampled, sampling.sampled_size, LLAMA_TOKEN_NULL);
         }
     }
@@ -1814,9 +1815,11 @@ void llama_context::output_reorder() {
         if (!sampling.logits_count.empty()) {
             std::swap(sampling.logits_count[i0], sampling.logits_count[i1]);
         }
+
         if (!sampling.probs_count.empty()) {
             std::swap(sampling.probs_count[i0], sampling.probs_count[i1]);
         }
+
         if (!sampling.candidates_count.empty()) {
             std::swap(sampling.candidates_count[i0], sampling.candidates_count[i1]);
         }