server : fix speculative decoding with context shift (#10641)

* server : fix speculative decoding with context shift

ggml-ci

* server : take into account speculative limits

ggml-ci

* server : add tests

examples/server/tests/unit/test_speculative.py

@@ -82,6 +82,37 @@ def test_different_draft_min_draft_max():
         last_content = res.body["content"]
 
 
+def test_slot_ctx_not_exceeded():
+    global server
+    server.n_ctx = 64
+    server.start()
+    res = server.make_request("POST", "/completion", data={
+        "prompt": "Hello " * 56,
+        "temperature": 0.0,
+        "top_k": 1,
+        "speculative.p_min": 0.0,
+    })
+    assert res.status_code == 200
+    assert len(res.body["content"]) > 0
+
+
+def test_with_ctx_shift():
+    global server
+    server.n_ctx = 64
+    server.start()
+    res = server.make_request("POST", "/completion", data={
+        "prompt": "Hello " * 56,
+        "temperature": 0.0,
+        "top_k": 1,
+        "n_predict": 64,
+        "speculative.p_min": 0.0,
+    })
+    assert res.status_code == 200
+    assert len(res.body["content"]) > 0
+    assert res.body["tokens_predicted"] == 64
+    assert res.body["truncated"] == True
+
+
 @pytest.mark.parametrize("n_slots,n_requests", [
     (1, 2),
     (2, 2),