feat: Add Ollama embedding support for local embedding models

apps/base_rag_example.py

@@ -75,7 +75,7 @@ class BaseRAGExample(ABC):
             "--embedding-mode",
             type=str,
             default="sentence-transformers",
-            choices=["sentence-transformers", "openai", "mlx"],
+            choices=["sentence-transformers", "openai", "mlx", "ollama"],
             help="Embedding backend mode (default: sentence-transformers)",
         )
 
@@ -85,7 +85,7 @@ class BaseRAGExample(ABC):
             "--llm",
             type=str,
             default="openai",
-            choices=["openai", "ollama", "hf"],
+            choices=["openai", "ollama", "hf", "simulated"],
             help="LLM backend to use (default: openai)",
         )
         llm_group.add_argument(

packages/leann-backend-diskann/leann_backend_diskann/diskann_embedding_server.py

@@ -261,7 +261,7 @@ if __name__ == "__main__":
         "--embedding-mode",
         type=str,
         default="sentence-transformers",
-        choices=["sentence-transformers", "openai", "mlx"],
+        choices=["sentence-transformers", "openai", "mlx", "ollama"],
         help="Embedding backend mode",
     )
     parser.add_argument(

packages/leann-backend-hnsw/leann_backend_hnsw/hnsw_embedding_server.py

@@ -295,7 +295,7 @@ if __name__ == "__main__":
         "--embedding-mode",
         type=str,
         default="sentence-transformers",
-        choices=["sentence-transformers", "openai", "mlx"],
+        choices=["sentence-transformers", "openai", "mlx", "ollama"],
         help="Embedding backend mode",
     )
 

packages/leann-core/src/leann/cli.py

@@ -94,6 +94,13 @@ Examples:
             "--backend", type=str, default="hnsw", choices=["hnsw", "diskann"]
         )
         build_parser.add_argument("--embedding-model", type=str, default="facebook/contriever")
+        build_parser.add_argument(
+            "--embedding-mode",
+            type=str,
+            default="sentence-transformers",
+            choices=["sentence-transformers", "openai", "mlx", "ollama"],
+            help="Embedding backend mode (default: sentence-transformers)",
+        )
         build_parser.add_argument("--force", "-f", action="store_true", help="Force rebuild")
         build_parser.add_argument("--graph-degree", type=int, default=32)
         build_parser.add_argument("--complexity", type=int, default=64)
@@ -469,6 +476,7 @@ Examples:
         builder = LeannBuilder(
             backend_name=args.backend,
             embedding_model=args.embedding_model,
+            embedding_mode=args.embedding_mode,
             graph_degree=args.graph_degree,
             complexity=args.complexity,
             is_compact=args.compact,

packages/leann-core/src/leann/embedding_compute.py

@@ -35,7 +35,7 @@ def compute_embeddings(
     Args:
         texts: List of texts to compute embeddings for
         model_name: Model name
-        mode: Computation mode ('sentence-transformers', 'openai', 'mlx')
+        mode: Computation mode ('sentence-transformers', 'openai', 'mlx', 'ollama')
         is_build: Whether this is a build operation (shows progress bar)
         batch_size: Batch size for processing
         adaptive_optimization: Whether to use adaptive optimization based on batch size
@@ -55,6 +55,8 @@ def compute_embeddings(
         return compute_embeddings_openai(texts, model_name)
     elif mode == "mlx":
         return compute_embeddings_mlx(texts, model_name)
+    elif mode == "ollama":
+        return compute_embeddings_ollama(texts, model_name, is_build=is_build)
     else:
         raise ValueError(f"Unsupported embedding mode: {mode}")
 
@@ -365,3 +367,117 @@ def compute_embeddings_mlx(chunks: list[str], model_name: str, batch_size: int =
 
     # Stack numpy arrays
     return np.stack(all_embeddings)
+
+
+def compute_embeddings_ollama(
+    texts: list[str], model_name: str, is_build: bool = False, host: str = "http://localhost:11434"
+) -> np.ndarray:
+    """
+    Compute embeddings using Ollama API.
+
+    Args:
+        texts: List of texts to compute embeddings for
+        model_name: Ollama model name (e.g., "nomic-embed-text-v2", "mxbai-embed-large")
+        is_build: Whether this is a build operation (shows progress bar)
+        host: Ollama host URL (default: http://localhost:11434)
+
+    Returns:
+        Normalized embeddings array, shape: (len(texts), embedding_dim)
+    """
+    try:
+        import requests
+    except ImportError:
+        raise ImportError(
+            "The 'requests' library is required for Ollama embeddings. Install with: uv pip install requests"
+        )
+
+    if not texts:
+        raise ValueError("Cannot compute embeddings for empty text list")
+
+    logger.info(
+        f"Computing embeddings for {len(texts)} texts using Ollama API, model: '{model_name}'"
+    )
+
+    # Check if Ollama is running
+    try:
+        response = requests.get(f"{host}/api/version", timeout=5)
+        response.raise_for_status()
+    except Exception as e:
+        raise RuntimeError(
+            f"Could not connect to Ollama at {host}. Please ensure Ollama is running. Error: {e}"
+        )
+
+    # Check if model exists
+    try:
+        response = requests.get(f"{host}/api/tags", timeout=5)
+        response.raise_for_status()
+        models = response.json()
+        model_names = [model["name"] for model in models.get("models", [])]
+
+        # Check if model exists (handle versioned names like nomic-embed-text-v2:latest)
+        model_found = any(
+            model_name in name or name.startswith(f"{model_name}:") for name in model_names
+        )
+
+        if not model_found:
+            error_msg = f"Model '{model_name}' not found in Ollama. Available models: {', '.join(model_names)}"
+            error_msg += f"\n\nTo install the model, run:\n  ollama pull {model_name}"
+            raise ValueError(error_msg)
+    except requests.exceptions.RequestException as e:
+        logger.warning(f"Could not verify model existence: {e}")
+
+    # Process embeddings
+    all_embeddings = []
+    batch_size = 100  # Process in batches to avoid overwhelming the API
+
+    # Add progress bar if in build mode
+    try:
+        if is_build:
+            from tqdm import tqdm
+
+            batch_iterator = tqdm(
+                range(0, len(texts), batch_size),
+                desc="Computing Ollama embeddings",
+                unit="batch",
+                total=(len(texts) + batch_size - 1) // batch_size,
+            )
+        else:
+            batch_iterator = range(0, len(texts), batch_size)
+    except ImportError:
+        batch_iterator = range(0, len(texts), batch_size)
+
+    for i in batch_iterator:
+        batch_texts = texts[i : i + batch_size]
+
+        for text in batch_texts:
+            try:
+                response = requests.post(
+                    f"{host}/api/embeddings", json={"model": model_name, "prompt": text}, timeout=30
+                )
+                response.raise_for_status()
+
+                result = response.json()
+                embedding = result.get("embedding")
+
+                if embedding is None:
+                    raise ValueError(f"No embedding returned for text: {text[:50]}...")
+
+                all_embeddings.append(embedding)
+
+            except requests.exceptions.RequestException as e:
+                logger.error(f"Failed to get embedding for text: {e}")
+                raise RuntimeError(f"Error getting embedding from Ollama: {e}")
+            except Exception as e:
+                logger.error(f"Unexpected error: {e}")
+                raise
+
+    # Convert to numpy array and normalize
+    embeddings = np.array(all_embeddings, dtype=np.float32)
+
+    # Normalize embeddings (L2 normalization)
+    norms = np.linalg.norm(embeddings, axis=1, keepdims=True)
+    embeddings = embeddings / (norms + 1e-8)  # Add small epsilon to avoid division by zero
+
+    logger.info(f"Generated {len(embeddings)} embeddings, dimension: {embeddings.shape[1]}")
+
+    return embeddings