pinecone: init pkg (#16556)

<!-- Thank you for contributing to LangChain!

Please title your PR "<package>: <description>", where <package> is
whichever of langchain, community, core, experimental, etc. is being
modified.

Replace this entire comment with:
  - **Description:** a description of the change, 
  - **Issue:** the issue # it fixes if applicable,
  - **Dependencies:** any dependencies required for this change,
- **Twitter handle:** we announce bigger features on Twitter. If your PR
gets announced, and you'd like a mention, we'll gladly shout you out!

Please make sure your PR is passing linting and testing before
submitting. Run `make format`, `make lint` and `make test` from the root
of the package you've modified to check this locally.

See contribution guidelines for more information on how to write/run
tests, lint, etc: https://python.langchain.com/docs/contributing/

If you're adding a new integration, please include:
1. a test for the integration, preferably unit tests that do not rely on
network access,
2. an example notebook showing its use. It lives in
`docs/docs/integrations` directory.

If no one reviews your PR within a few days, please @-mention one of
@baskaryan, @eyurtsev, @hwchase17.
 -->

libs/partners/pinecone/langchain_pinecone/_utilities.py

@@ -0,0 +1,71 @@
+from enum import Enum
+from typing import List, Union
+
+import numpy as np
+import simsimd  # type: ignore
+
+Matrix = Union[List[List[float]], List[np.ndarray], np.ndarray]
+
+
+class DistanceStrategy(str, Enum):
+    """Enumerator of the Distance strategies for calculating distances
+    between vectors."""
+
+    EUCLIDEAN_DISTANCE = "EUCLIDEAN_DISTANCE"
+    MAX_INNER_PRODUCT = "MAX_INNER_PRODUCT"
+    COSINE = "COSINE"
+
+
+def maximal_marginal_relevance(
+    query_embedding: np.ndarray,
+    embedding_list: list,
+    lambda_mult: float = 0.5,
+    k: int = 4,
+) -> List[int]:
+    """Calculate maximal marginal relevance."""
+    if min(k, len(embedding_list)) <= 0:
+        return []
+    if query_embedding.ndim == 1:
+        query_embedding = np.expand_dims(query_embedding, axis=0)
+    similarity_to_query = cosine_similarity(query_embedding, embedding_list)[0]
+    most_similar = int(np.argmax(similarity_to_query))
+    idxs = [most_similar]
+    selected = np.array([embedding_list[most_similar]])
+    while len(idxs) < min(k, len(embedding_list)):
+        best_score = -np.inf
+        idx_to_add = -1
+        similarity_to_selected = cosine_similarity(embedding_list, selected)
+        for i, query_score in enumerate(similarity_to_query):
+            if i in idxs:
+                continue
+            redundant_score = max(similarity_to_selected[i])
+            equation_score = (
+                lambda_mult * query_score - (1 - lambda_mult) * redundant_score
+            )
+            if equation_score > best_score:
+                best_score = equation_score
+                idx_to_add = i
+        idxs.append(idx_to_add)
+        selected = np.append(selected, [embedding_list[idx_to_add]], axis=0)
+    return idxs
+
+
+def cosine_similarity(X: Matrix, Y: Matrix) -> np.ndarray:
+    """Row-wise cosine similarity between two equal-width matrices."""
+    if len(X) == 0 or len(Y) == 0:
+        return np.array([])
+
+    X = np.array(X)
+    Y = np.array(Y)
+    if X.shape[1] != Y.shape[1]:
+        raise ValueError(
+            f"Number of columns in X and Y must be the same. X has shape {X.shape} "
+            f"and Y has shape {Y.shape}."
+        )
+
+    X = np.array(X, dtype=np.float32)
+    Y = np.array(Y, dtype=np.float32)
+    Z = 1 - simsimd.cdist(X, Y, metric="cosine")
+    if isinstance(Z, float):
+        return np.array([Z])
+    return Z