utils.py

import math

import config


def get_map_center():
    """Returns center of the map"""
    lat = (config.MAP_END[0] + config.MAP_START[0]) / 2
    lon = (config.MAP_END[1] + config.MAP_START[1]) / 2
    return lat, lon


def get_start_coords(worker_no):
    """Returns center of square for given worker"""
    grid = config.GRID
    total_workers = grid[0] * grid[1]
    per_column = total_workers / grid[0]
    column = worker_no % per_column
    row = worker_no / per_column
    part_lat = (config.MAP_END[0] - config.MAP_START[0]) / float(grid[0])
    part_lon = (config.MAP_END[1] - config.MAP_START[1]) / float(grid[1])
    start_lat = config.MAP_START[0] + part_lat * row + part_lat / 2
    start_lon = config.MAP_START[1] + part_lon * column + part_lon / 2
    return start_lat, start_lon


def float_range(start, end, step):
    """xrange for floats, also capable of iterating backwards"""
    if start > end:
        while end < start:
            yield start
            start += -step
    else:
        while start < end:
            yield start
            start += step


def get_points_per_worker():
    """Returns all points that should be visited for whole grid"""
    total_workers = config.GRID[0] * config.GRID[1]
    lat_gain = getattr(config, 'LAT_GAIN', 0.0015)
    lon_gain = getattr(config, 'LON_GAIN', 0.0025)
    points = [[] for _ in range(total_workers)]
    total_rows = math.ceil(
        abs(config.MAP_START[0] - config.MAP_END[0]) / lat_gain
    )
    total_columns = math.ceil(
        abs(config.MAP_START[1] - config.MAP_END[1]) / lon_gain
    )
    for map_row, lat in enumerate(
        float_range(config.MAP_START[0], config.MAP_END[0], lat_gain)
    ):
        for map_col, lon in enumerate(
            float_range(config.MAP_START[1], config.MAP_END[1], lon_gain)
        ):
            # Figure out which worker this should go to
            grid_row = int(map_row / float(total_rows) * config.GRID[0])
            grid_col = int(map_col / float(total_columns) * config.GRID[1])
            worker_no = grid_row * config.GRID[1] + grid_col
            points[worker_no].append((lat, lon))
    return points