ALLEN INSTITUTE

# Source code for bmtk.builder.auxi.edge_connectors

    # Copyright 2017. Allen Institute. All rights reserved
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    import numpy as np
    import random

    def distance_connector(source, target, d_weight_min, d_weight_max, d_max, nsyn_min, nsyn_max):
        # Avoid self-connections.
        sid = source.node_id
        tid = target.node_id
        if sid == tid:
            return None

        # first create weights by euclidean distance between cells
        r = np.linalg.norm(np.array(source['positions']) - np.array(target['positions']))
        if r > d_max:
            dw = 0.0
        else:
            t = r / d_max
            dw = d_weight_max * (1.0 - t) + d_weight_min * t

        # drop the connection if the weight is too low
        if dw <= 0:
            return None

        # filter out nodes by treating the weight as a probability of connection
        if random.random() > dw:
            return None

        # Add the number of synapses for every connection.
        tmp_nsyn = random.randint(nsyn_min, nsyn_max)
        return tmp_nsyn

    def connect_random(source, target, nsyn_min=0, nsyn_max=10, distribution=None):
        return np.random.randint(nsyn_min, nsyn_max)