[Continuous batching] Add finish reason to generation output

src/cpp/include/openvino/genai/generation_handle.hpp

@@ -32,6 +32,12 @@ struct EncodedGenerationResult {
     GenerationStatus m_status = GenerationStatus::RUNNING;
 };
 
+enum class GenerationFinishReason {
+    NONE = 0, // Default value, when generation is not yet finished
+    STOP = 1, // Generation finished naturally, by reaching end of sequence token
+    LENGTH = 2 // Generation finished by reaching max_new_tokens limit
+};
+
 struct GenerationResult {
     // request ID - obsolete when handle API is approved as handle will connect results with prompts.
     uint64_t m_request_id;
@@ -49,6 +55,7 @@ struct GenerationResult {
 struct GenerationOutput {
     std::vector<int64_t> generated_token_ids;
     float score;
+    GenerationFinishReason finish_reason;
 };
 
 using GenerationOutputs = std::unordered_map<uint64_t, GenerationOutput>;

src/cpp/src/generation_handle.cpp

@@ -36,6 +36,7 @@ void add_partial_result(std::unordered_map<uint64_t, GenerationOutput>& partial_
         } else {
             partial_result_iter->second.generated_token_ids.push_back(iteration_result.second.generated_token_ids[0]);
             partial_result_iter->second.score = iteration_result.second.score;
+            partial_result_iter->second.finish_reason = iteration_result.second.finish_reason;
         }
     }
 }

src/cpp/src/sampler.hpp

@@ -193,6 +193,8 @@ class GroupBeamSearcher {
 
                     // mark current sequence as finished
                     beam.m_sequence->set_status(SequenceStatus::FINISHED);
+                    // Setting length since this function is used when sequence generated tokens number reaches max_new_tokens 
+                    beam.m_sequence->set_finish_reason(GenerationFinishReason::LENGTH);
                     // we also need to drop add ongoing / forked sequences from scheduler
                     sampler_output.m_dropped_sequences.push_back(sequence_id);
                 }
@@ -432,6 +434,8 @@ void GroupBeamSearcher::select_next_tokens(const ov::Tensor& logits, SamplerOutp
             Sequence::Ptr forked_sequence = m_sequence_group->fork_sequence(candidate.m_sequence);
             // and finish immidiately
             forked_sequence->set_status(SequenceStatus::FINISHED);
+            // Setting length since this function is used when sequence generated eos token
+            forked_sequence->set_finish_reason(GenerationFinishReason::STOP);
 
             // TODO: make it more simplier
             // currently, we finish sequence and then fork it in current code

src/cpp/src/sequence_group.hpp

@@ -33,6 +33,7 @@ class Sequence {
     uint64_t m_grouped_id;
     uint64_t m_id = _get_next_global_sequence_id();
     SequenceStatus m_status = SequenceStatus::RUNNING;
+    GenerationFinishReason m_finish_reason = GenerationFinishReason::NONE;
     float m_cumulative_log_prob = 0.0f;
 
 public:
@@ -91,6 +92,14 @@ class Sequence {
         m_status = status;
     }
 
+    GenerationFinishReason get_finish_reason() const {
+        return m_finish_reason;
+    }
+
+    void set_finish_reason(GenerationFinishReason finish_reason) {
+        m_finish_reason = finish_reason;
+    }
+
     // appends new tokens to a generated part
     void append_token(int64_t token_id, float log_prob) {
         m_cumulative_log_prob += log_prob;
@@ -102,6 +111,7 @@ class Sequence {
         OPENVINO_ASSERT(m_generated_ids.size());
         output.score = get_cumulative_log_probs();
         output.generated_token_ids = std::vector<int64_t> {m_generated_ids.back()};
+        output.finish_reason = get_finish_reason();
         return output;
     }
 
@@ -205,6 +215,13 @@ class SequenceGroup {
                 running_sequence->get_generated_ids().back() == m_sampling_params.eos_token_id && !m_sampling_params.ignore_eos) {
                 // stop sequence by max_new_tokens or EOS token
                 running_sequence->set_status(SequenceStatus::FINISHED);
+
+                if (running_sequence->get_generated_ids().back() == m_sampling_params.eos_token_id && !m_sampling_params.ignore_eos) {
+                    running_sequence->set_finish_reason(GenerationFinishReason::STOP);
+                } else if (m_sampling_params.max_new_tokens == generated_len) {
+                    running_sequence->set_finish_reason(GenerationFinishReason::LENGTH);
+                }
+
                 dropped_seq_ids.push_back(running_sequence->get_id());
             }
         }
@@ -451,15 +468,15 @@ class SequenceGroup {
         for (auto& sequence: m_sequences) {
             GenerationOutput output;
             output.generated_token_ids = sequence->get_generated_ids();
-            output.score = sequence->get_beam_search_score(m_sampling_params);
+            output.score = m_sampling_params.is_beam_search() ? sequence->get_beam_search_score(m_sampling_params) : sequence->get_cumulative_log_probs();
+            output.finish_reason = sequence->get_finish_reason();
             outputs.emplace(sequence->get_grouped_id(), output);
         }
         m_generation_stream->push(outputs);
     }
 
     void push_partial_outputs() {
         GenerationOutputs outputs;
-        // TODO: support streamimg for n seqs
         for (auto& sequence : m_sequences) {
             // todo: check seq.is_finished() to generate without several </s>
             // or is it ok to use padding?