tests: avoid constantly reallocating logits

tests/test_llama.py

@@ -47,16 +47,22 @@ def test_llama_cpp_tokenization():
 @pytest.fixture
 def mock_llama(monkeypatch):
     def setup_mock(llama: llama_cpp.Llama, output_text: str):
+        n_ctx = llama.n_ctx()
         n_vocab = llama.n_vocab()
         output_tokens = llama.tokenize(
             output_text.encode("utf-8"), add_bos=True, special=True
         )
+        logits = (llama_cpp.c_float * (n_vocab * n_ctx))(-100.0)
+        for i in range(n_ctx):
+            output_idx = i + 1  # logits for first tokens predict second token
+            if output_idx < len(output_tokens):
+                logits[i * n_vocab + output_tokens[output_idx]] = 100.0
+            else:
+                logits[i * n_vocab + llama.token_eos()] = 100.0
         n = 0
         last_n_tokens = 0
 
         def mock_decode(ctx: llama_cpp.llama_context_p, batch: llama_cpp.llama_batch):
-            nonlocal n
-            nonlocal last_n_tokens
             # Test some basic invariants of this mocking technique
             assert ctx == llama._ctx.ctx, "context does not match mock_llama"
             assert batch.n_tokens > 0, "no tokens in batch"
@@ -70,26 +76,22 @@ def mock_llama(monkeypatch):
                 batch.n_tokens - 1
             ], "logits not allocated for last token"
             # Update the mock context state
+            nonlocal n
+            nonlocal last_n_tokens
             n = max(batch.pos[i] for i in range(batch.n_tokens)) + 1
             last_n_tokens = batch.n_tokens
             return 0
 
-        def mock_get_logits(*args, **kwargs):
-            nonlocal n
-            nonlocal last_n_tokens
+        def mock_get_logits(ctx: llama_cpp.llama_context_p):
+            # Test some basic invariants of this mocking technique
+            assert ctx == llama._ctx.ctx, "context does not match mock_llama"
             assert n > 0, "mock_llama_decode not called"
             assert last_n_tokens > 0, "mock_llama_decode not called"
-            logits = (llama_cpp.c_float * (last_n_tokens * n_vocab))(-100.0)
-            for logits_idx, output_idx in enumerate(
-                range(n - last_n_tokens + 1, n + 1)
-            ):
-                if output_idx < len(output_tokens):
-                    logits[
-                        logits_idx * last_n_tokens + output_tokens[output_idx]
-                    ] = 100.0
-                else:
-                    logits[logits_idx * last_n_tokens + llama.token_eos()] = 100.0
-            return logits
+            # Return view of logits for last_n_tokens
+            return (llama_cpp.c_float * (last_n_tokens * n_vocab)).from_address(
+                ctypes.addressof(logits)
+                + (n - last_n_tokens) * n_vocab * ctypes.sizeof(llama_cpp.c_float)
+            )
 
         monkeypatch.setattr("llama_cpp.llama_cpp.llama_decode", mock_decode)
         monkeypatch.setattr("llama_cpp.llama_cpp.llama_get_logits", mock_get_logits)