Fix chat template, add test for chat scenario

.github/workflows/causal_lm_cpp.yml

@@ -524,3 +524,63 @@ jobs:
           && export PYTHONPATH=./build/:$PYTHONPATH
           && timeout 50s samples/python/greedy_causal_lm/greedy_causal_lm.py ./redpajama-3b-chat/ "Alan Turing was a"
           | diff ./pred_greedy.txt -
+
+  cpp-chat_sample-ubuntu:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+      - uses: actions/setup-python@v4
+        with:
+          python-version: 3.8
+      - name: Install OpenVINO
+        run: |
+          mkdir ./ov/
+          curl ${{ env.l_ov_link }} | tar --directory ./ov/ --strip-components 1 -xz
+          sudo ./ov/install_dependencies/install_openvino_dependencies.sh
+      - name: Download, convert and build
+        run: |
+          source ./ov/setupvars.sh
+          python -m pip install --upgrade-strategy eager -r ./samples/requirements.txt --pre --extra-index-url https://storage.openvinotoolkit.org/simple/wheels/nightly
+          python -m pip install ./thirdparty/openvino_tokenizers/[transformers] --pre --extra-index-url https://storage.openvinotoolkit.org/simple/wheels/nightly
+          optimum-cli export openvino --trust-remote-code --weight-format fp16 --model TinyLlama/TinyLlama-1.1B-Chat-v1.0 TinyLlama-1.1B-Chat-v1.0
+          cmake -DCMAKE_BUILD_TYPE=Release -S ./ -B ./build/
+          cmake --build ./build/ --config Release -j
+      - name: Compare
+        run: |
+          source ./ov/setupvars.sh
+          printf 'What is 2 + 2?\nWhat is the previous answer?\nAdd 1 to it.\nSubtract 5 from it.\nWhy is the sun yellow?\nWhat was my first question?\nStop!\n' > ./input.txt
+          timeout 30s ./build/samples/cpp/chat_sample/chat_sample ./TinyLlama-1.1B-Chat-v1.0/ < input.txt > ./pred.txt
+          python -c "
+          from transformers import LlamaTokenizer, AutoModelForCausalLM
+          model_id = 'TinyLlama/TinyLlama-1.1B-Chat-v1.0'
+          tokenizer = LlamaTokenizer.from_pretrained(model_id)
+          model = AutoModelForCausalLM.from_pretrained(model_id)
+          prompts = ['What is 2 + 2?', 'What is the previous answer?', 'Add 1 to it.', 'Subtract 5 from it.', 'Why is the sun yellow?', 'What was my first question?']
+          def gen_prompt(prompt):
+              return {'role': 'user', 'content': prompt}
+          def gen_answer(answer):
+              return {'role': 'assistant', 'content': answer}
+          chat_history = []
+          chat_prompt = ''
+          output = open('ref.txt', 'w')
+          for prompt in prompts:
+              output.write('question:\n')
+              chat_history.append(gen_prompt(prompt))
+              chat_prompt = tokenizer.apply_chat_template(chat_history, tokenize=False, add_generation_prompt=True)
+              tokenized = tokenizer(chat_prompt, return_tensors='pt')
+              answer = model.generate(**tokenized, max_length=1000, do_sample=False)
+              answer_str = tokenizer.decode(answer[0, tokenized['input_ids'].numel():], skip_special_tokens=True)
+              chat_history.append(gen_answer(answer_str))
+              output.write(answer_str)
+              output.write('\n----------\n')
+          output.write('question:\n')
+          output.close()
+          "
+          diff pred.txt ref.txt
+          echo "Chat sample cpp" passed
+          export PYTHONPATH=./build/:$PYTHONPATH
+          timeout 30s ./samples/python/chat_sample/chat_sample.py ./TinyLlama-1.1B-Chat-v1.0/ < input.txt > ./pred2.txt
+          diff pred2.txt ref.txt
+          echo "Chat sample python" passed

src/cpp/src/llm_pipeline.cpp

@@ -14,6 +14,24 @@
 #include "utils.hpp"
 #include "text_callback_streamer.hpp"
 
+namespace {
+
+ov::genai::TokenizedInputs subtract_chat_tokenized_inputs(const ov::genai::TokenizedInputs& fisrt, const ov::genai::TokenizedInputs& second){
+    auto first_size = fisrt.input_ids.get_size();
+    auto second_size = second.input_ids.get_size();
+    ov::Shape new_shape{1, first_size - second_size};
+
+    ov::Tensor new_input_ids(ov::element::i64, new_shape);
+    auto data_ptr = fisrt.input_ids.data<int64_t>();
+    std::copy(data_ptr + second_size, data_ptr + first_size, new_input_ids.data<int64_t>());
+
+    ov::Tensor new_attention_mask(ov::element::i64, new_shape);
+    std::fill_n(new_attention_mask.data<int64_t>(), new_shape[1], 1);
+
+    return {new_input_ids, new_attention_mask};
+}
+}
+
 namespace ov {
 namespace genai {
 
@@ -101,12 +119,17 @@ class StatefulLLMPipeline final : public LLMPipelineImplBase {
                 m_history.push_back({{"role", "user"}, {"content", prompt}});
                 constexpr bool add_generation_prompt = true;
                 auto new_templated_chat_history  = m_tokenizer.apply_chat_template(m_history, add_generation_prompt);
-
-                prompt = new_templated_chat_history.substr(m_templated_chat_history.size());
+                auto new_chat_tokens = m_tokenizer.encode(new_templated_chat_history);
+                if (m_is_cache_empty) {
+                    encoded_input = new_chat_tokens;
+                } else {
+                    auto prev_chat_tokens = m_tokenizer.encode(m_templated_chat_history);
+                    encoded_input = subtract_chat_tokenized_inputs(new_chat_tokens, prev_chat_tokens);
+                }
                 m_templated_chat_history = new_templated_chat_history;
+            } else {
+                encoded_input = m_tokenizer.encode(prompt);
             }
-
-            encoded_input = m_tokenizer.encode(prompt);
         }
 
         auto encoded_results  = generate(encoded_input, config, streamer);