feat(backend): use the new batch api from llama

backends/llamacpp/csrc/backend.cpp

@@ -38,6 +38,31 @@ namespace huggingface::tgi::backends::llamacpp {
         return {pSampler, llama_sampler_deleter};
     }
 
+
+    std::expected<llama_batch, backend_error_t> get_batch_from_prompt(std::span<llama_token> prompt) {
+        auto batch = llama_batch_init(static_cast<int32_t>(prompt.size()), 0, 1);
+        std::for_each(prompt.begin(), prompt.end(), [&batch](const llama_token token) {
+            const auto n_token = batch.n_tokens;
+
+            batch.token[n_token] = token;
+            batch.pos[n_token] = n_token;
+            batch.n_seq_id[n_token] = 1;
+            batch.seq_id[n_token][0] = 1;
+            batch.logits[n_token] = false;
+            batch.n_tokens++;
+        });
+
+        batch.logits[batch.n_tokens - 1] = true;
+        return batch;
+    }
+
+    void update_batch_for_decoding(llama_batch &batch, llama_token token, size_t position) {
+        batch.n_tokens = 1;
+        batch.logits[0] = true;
+        batch.token[0] = token;
+        batch.pos[0] = static_cast<int32_t>(position);
+    }
+
     worker_t::worker_t(std::shared_ptr<llama_model> model, const llama_context_params &&params)
             : model_(model), context_(llama_new_context_with_model(model_.get(), params)) {
 
@@ -59,11 +84,11 @@ namespace huggingface::tgi::backends::llamacpp {
         auto sampler = generation_context.sampling_params.into_llama_sampler(model_.get());
 
         // Set up the prompt
-        auto copy = std::vector(generation_context.input_tokens.begin(), generation_context.input_tokens.end());
+        if (auto maybe_batch = get_batch_from_prompt(generation_context.input_tokens); maybe_batch.has_value()) {
-        auto batch = llama_batch_get_one(copy.data(), copy.size());
-
             // Decode
+            auto batch = *maybe_batch;
             auto n_decoded_tokens = 0;
+            const auto prompt_size = generation_context.input_tokens.size();
             for (bool generating = true; generating; ++n_decoded_tokens) {
 
 #ifdef TGI_LLAMACPP_BACKEND_DEBUG
@@ -79,24 +104,30 @@ namespace huggingface::tgi::backends::llamacpp {
                 if (LLAMA_SUCCESS(status)) [[likely]] {
                     // Sample the new token
                     auto new_token_id = llama_sampler_sample(sampler.get(), context_.get(), -1);
-                auto is_eog = llama_token_is_eog(model_.get(), new_token_id);
+                    const auto is_eog = llama_token_is_eog(model_.get(), new_token_id);
-                auto new_token_logits = 0.0f; // TODO: return logit
+                    const auto new_token_logits = llama_get_logits_ith(context_.get(), -1); // TODO: return logit
 
                     // Handle termination cases
-                const auto has_reach_max_tokens = n_decoded_tokens >= max_new_tokens - 1;
+                    const bool has_reach_max_tokens = n_decoded_tokens >= max_new_tokens - 1;
-                const auto has_reach_eog = !generation_context.generation_params.ignore_eos_token & is_eog;
+                    const bool has_reach_eog = !generation_context.generation_params.ignore_eos_token & is_eog;
-
+                    const bool is_final = has_reach_max_tokens | has_reach_eog;
-                generating = !(has_reach_max_tokens | has_reach_eog);
 
                     // Bubble up the generated token if a callback is provided
-                const auto should_stop =
+                    const auto should_stop = callback_(new_token_id, *new_token_logits, is_final, n_decoded_tokens + 1);
-                        std::invoke(callback_, new_token_id, new_token_logits, !generating, n_decoded_tokens + 1);
-                generating ^= should_stop;
 
-                batch = llama_batch_get_one(&new_token_id, 1);
+                    // Compute the continuation flag
+                    generating = !(should_stop | is_final);
+
+                    // Update the batch for the next generation
+                    update_batch_for_decoding(batch, new_token_id, prompt_size + n_decoded_tokens);
                 }
             }
 
+            llama_batch_free(batch);
+
             return n_decoded_tokens;
+        } else {
+            return maybe_batch.error();
+        }
     }
 }

backends/llamacpp/csrc/backend.hpp

@@ -75,7 +75,7 @@ namespace huggingface::tgi::backends::llamacpp {
     struct generation_context_t {
         generation_params_t generation_params;
         sampling_params_t sampling_params;
-        std::span<const llama_token> input_tokens;
+        std::span<llama_token> input_tokens;
     };
 
     /**