server : add --no-context-shift option

common/arg.cpp

@@ -691,7 +691,7 @@ gpt_params_context gpt_params_parser_init(gpt_params & params, llama_example ex,
         [](gpt_params & params) {
             params.ctx_shift = false;
         }
-    ).set_examples({LLAMA_EXAMPLE_MAIN}));
+    ).set_examples({LLAMA_EXAMPLE_MAIN, LLAMA_EXAMPLE_SERVER}));
     add_opt(llama_arg(
         {"--chunks"}, "N",
         format("max number of chunks to process (default: %d, -1 = all)", params.n_chunks),

examples/server/server.cpp

@@ -1180,6 +1180,15 @@ struct server_context {
             SLT_DBG(slot, "stopped by limit, n_decoded = %d, n_predict = %d\n", slot.n_decoded, slot.params.n_predict);
         }
 
+        // if context shift is disabled, we stop when it reaches the context limit
+        if (slot.n_decoded >= slot.n_ctx) {
+            slot.truncated      = true;
+            slot.stopped_limit  = true;
+            slot.has_next_token = false;
+
+            SLT_DBG(slot, "stopped due to running out of context capacity, n_decoded = %d, n_ctx = %d\n", slot.n_decoded, slot.n_ctx);
+        }
+
         if (llama_token_is_eog(model, result.tok)) {
             slot.stopped_eos    = true;
             slot.has_next_token = false;
@@ -1480,7 +1489,7 @@ struct server_context {
             if (result.error) {
                 error_handler(result.data);
                 cancel_tasks(id_tasks);
-                break;
+                return;
             }
 
             size_t idx = result.data["index"];
@@ -1827,6 +1836,14 @@ struct server_context {
         for (server_slot & slot : slots) {
             if (slot.ga_n == 1) {
                 if (slot.is_processing() && (int) system_tokens.size() + slot.n_past >= slot.n_ctx - 1) {
+                    if (!params.ctx_shift) {
+                        // this check is redundant (for good)
+                        // we should never get here, since n_predict is already limited
+                        slot.release();
+                        send_error(slot, "context shift is disabled", ERROR_TYPE_SERVER);
+                        continue;
+                    }
+
                     // Shift context
                     const int n_keep    = slot.params.n_keep + add_bos_token;
                     const int n_left    = (int) system_tokens.size() + slot.n_past - n_keep;
@@ -1961,6 +1978,14 @@ struct server_context {
                                 continue;
                             }
                         } else {
+                            if (!params.ctx_shift) {
+                                // if context shift is disabled, we make sure prompt size is smaller than KV size
+                                if ((int) system_tokens.size() + slot.n_prompt_tokens >= slot.n_ctx) {
+                                    slot.release();
+                                    send_error(slot, "the request exceeds the available context size. try increasing the context size or enable context shift", ERROR_TYPE_INVALID_REQUEST);
+                                    continue;
+                                }
+                            }
                             if (slot.params.n_keep < 0) {
                                 slot.params.n_keep = slot.n_prompt_tokens;
                             }

examples/server/tests/features/ctx_shift.feature

@@ -0,0 +1,62 @@
+@llama.cpp
+@ctx_shift
+Feature: llama.cpp server
+
+  Background: Server startup
+    Given a server listening on localhost:8080
+    And   a model file tinyllamas/stories260K.gguf from HF repo ggml-org/models
+    And   a model file test-model.gguf
+    And   a model alias tinyllama-2
+    And   BOS token is 1
+    And   42 as server seed
+    And   256 KV cache size
+    And   32 as batch size
+    And   2 slots
+
+  Scenario: Inference with context shift
+    And   64 server max tokens to predict
+    Then  the server is starting
+    Then  the server is healthy
+    Given a prompt:
+    """
+    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+    Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+    Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
+    Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+    """
+    And   a completion request with no api error
+    Then  64 tokens are predicted matching fun|Annaks|popcorns|pictry|bowl
+    And   the completion is  truncated
+    And   109 prompt tokens are processed
+
+  Scenario Outline: Inference without context shift
+    And   <n_predict> server max tokens to predict
+    And   disable context shifting
+    Then  the server is starting
+    Then  the server is healthy
+    Given a prompt:
+    """
+    Hi how are you
+    """
+    And   a completion request with no api error
+    Then  <n_token_output> tokens are predicted matching twind|Anna
+    And   the completion is <truncated> truncated
+    And   8 prompt tokens are processed
+    Examples:
+      | n_predict | n_token_output | truncated |
+      | 64        | 64             | not       |
+      | -1        | 120            |           |
+
+  Scenario: Inference without context shift (expected error: prompt too long)
+    And   disable context shifting
+    Then  the server is starting
+    Then  the server is healthy
+    Given a prompt:
+    """
+    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+    Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+    Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
+    Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+    """
+    And   a completion request with 400 api error
+

examples/server/tests/features/embeddings.feature

@@ -12,9 +12,9 @@ Feature: llama.cpp server
     # the bert-bge-small model has context size of 512
     # since the generated prompts are as big as the batch size, we need to set the batch size to 512
     # ref: https://huggingface.co/BAAI/bge-small-en-v1.5/blob/5c38ec7c405ec4b44b94cc5a9bb96e735b38267a/config.json#L20
-    And   512 as batch size
-    And   512 as ubatch size
-    And   2048 KV cache size
+    And   128 as batch size
+    And   128 as ubatch size
+    And   512 KV cache size
     And   embeddings extraction
     Then  the server is starting
     Then  the server is healthy
@@ -26,6 +26,20 @@ Feature: llama.cpp server
     """
     Then embeddings are generated
 
+  Scenario: Embedding (error: prompt too long)
+    When embeddings are computed for:
+    """
+    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+    Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+    Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
+    Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+    Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+    Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
+    Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+    """
+    And  embeddings request with 500 api error
+
   Scenario: OAI Embeddings compatibility
     Given a model bert-bge-small
     When an OAI compatible embeddings computation request for:

examples/server/tests/features/steps/steps.py

@@ -77,6 +77,7 @@ def step_server_config(context, server_fqdn: str, server_port: str):
     context.response_format = None
     context.temperature = None
     context.lora_file = None
+    context.disable_ctx_shift = False
 
     context.tasks_result = []
     context.concurrent_tasks = []
@@ -148,7 +149,7 @@ def step_n_slots(context, n_slots: int):
 
 @step('{n_predict:d} server max tokens to predict')
 def step_server_n_predict(context, n_predict: int):
-    context.n_server_predict = n_predict
+    context.n_server_predict = n_predict if n_predict > 0 else None
 
 
 @step('{slot_save_path} as slot save path')
@@ -180,6 +181,9 @@ def step_server_embeddings(context):
 def step_server_metrics(context):
     context.server_metrics = True
 
+@step('disable context shifting')
+def step_server_metrics(context):
+    context.disable_ctx_shift = True
 
 @step("the server is starting")
 def step_start_server(context):
@@ -257,7 +261,7 @@ async def step_all_slots_status(context, expected_slot_status_string: Literal['i
 @step('a completion request with {api_error} api error')
 @async_run_until_complete
 async def step_request_completion(context, api_error: Literal['raised'] | str):
-    expect_api_error = api_error == 'raised'
+    expect_api_error = api_error == 'raised' or api_error != 'no'
     seeds = await completions_seed(context, num_seeds=1)
     completion = await request_completion(context.prompts.pop(),
                                           seeds[0] if seeds is not None else seeds,
@@ -272,8 +276,11 @@ async def step_request_completion(context, api_error: Literal['raised'] | str):
     context.tasks_result.append(completion)
     if context.debug:
         print(f"Completion response: {completion}")
-    if expect_api_error:
+    if api_error == 'raised':
         assert completion == 401, f"completion must be an 401 status code: {completion}"
+    elif api_error.isdigit():
+        api_error_code = int(api_error)
+        assert completion == api_error_code, f"completion must be an {api_error_code} status code: {completion}"
 
 
 @step('{predicted_n:d} tokens are predicted matching {re_content}')
@@ -645,6 +652,9 @@ def step_assert_embeddings(context):
     for embedding in context.embeddings:
         assert_embeddings(embedding)
 
+@step('embeddings request with {api_error_code:d} api error')
+def step_assert_embeddings(context, api_error_code: int):
+    assert context.embeddings == api_error_code, f"embeddings request must return code {api_error_code}, but got {context.embeddings}"
 
 @step('an OAI compatible embeddings computation request for')
 @async_run_until_complete
@@ -1089,15 +1099,17 @@ async def oai_chat_completions(user_prompt,
     return completion_response
 
 
-async def request_embedding(content, seed, base_url=None) -> list[list[float]]:
+async def request_embedding(content, seed, base_url=None) -> list[list[float]] | int:
     async with aiohttp.ClientSession(timeout=DEFAULT_TIMEOUT_SECONDS) as session:
         async with session.post(f'{base_url}/embedding',
                                 json={
                                     "content": content,
                                 }) as response:
-            assert response.status == 200
-            response_json = await response.json()
-            return [response_json['embedding']]
+            if response.status == 200:
+                response_json = await response.json()
+                return [response_json['embedding']]
+            else:
+                return response.status
 
 
 async def request_oai_embeddings(input, seed,
@@ -1372,6 +1384,8 @@ def start_server_background(context):
         server_args.append('--verbose')
     if context.lora_file:
         server_args.extend(['--lora', context.lora_file])
+    if context.disable_ctx_shift:
+        server_args.extend(['--no-context-shift'])
 
     args = [str(arg) for arg in [context.server_path, *server_args]]
     print(f"bench: starting server with: {' '.join(args)}")