utils/vector_index.py

import torch


def create_dense_embeddings(query, model, instruction=None):
    if instruction == None:
        dense_emb = model.encode([query]).tolist()
    else:
        dense_emb = model.encode([[instruction, query]]).tolist()
    return dense_emb


def create_sparse_embeddings(query, model, tokenizer):
    device = "cuda" if torch.cuda.is_available() else "cpu"
    inputs = tokenizer(query, return_tensors="pt").to(device)

    with torch.no_grad():
        logits = model(**inputs).logits

    inter = torch.log1p(torch.relu(logits[0]))
    token_max = torch.max(inter, dim=0)  # sum over input tokens
    nz_tokens = torch.where(token_max.values > 0)[0]
    nz_weights = token_max.values[nz_tokens]

    order = torch.sort(nz_weights, descending=True)
    nz_weights = nz_weights[order[1]]
    nz_tokens = nz_tokens[order[1]]
    return {
        "indices": nz_tokens.cpu().numpy().tolist(),
        "values": nz_weights.cpu().numpy().tolist(),
    }


def hybrid_score_norm(dense, sparse, alpha: float):
    """Hybrid score using a convex combination

    alpha * dense + (1 - alpha) * sparse

    Args:
        dense: Array of floats representing
        sparse: a dict of `indices` and `values`
        alpha: scale between 0 and 1
    """
    if alpha < 0 or alpha > 1:
        raise ValueError("Alpha must be between 0 and 1")
    hsparse = {
        "indices": sparse["indices"],
        "values": [v * (1 - alpha) for v in sparse["values"]],
    }
    
    hdense = [[v * alpha for v in dense[0]]]
    return hdense, hsparse