lbry-sdk/lbrynet/p2p/PriceModel.py
2018-11-09 16:52:42 -05:00

58 lines
2 KiB
Python

from decimal import Decimal
from lbrynet import conf
def get_default_price_model(blob_tracker, base_price, **kwargs):
return MeanAvailabilityWeightedPrice(blob_tracker, base_price, **kwargs)
class ZeroPrice:
def __init__(self):
self.base_price = 0.0
def calculate_price(self, blob):
return 0.0
class MeanAvailabilityWeightedPrice:
"""Calculate mean-blob-availability and stream-position weighted price for a blob
Attributes:
base_price (float): base price
alpha (float): constant, > 0.0 and <= 1.0, used to more highly
value blobs at the beginning of a stream.
alpha defaults to 1.0, which has a null effect
blob_tracker (BlobAvailabilityTracker): blob availability tracker
"""
def __init__(self, tracker, base_price=None, alpha=1.0):
self.blob_tracker = tracker
base_price = base_price if base_price is not None else conf.settings['data_rate']
self.base_price = Decimal(base_price)
self.alpha = Decimal(alpha)
def calculate_price(self, blob):
mean_availability = self.blob_tracker.last_mean_availability
availability = self.blob_tracker.availability.get(blob, [])
index = 0 # blob.index
availability_mult = self._get_availability_multiplier(mean_availability, availability)
price = self.base_price * availability_mult / self._frontload(index)
return round(price, 5)
def _get_availability_multiplier(self, mean_availability, availability):
return Decimal(max(1, mean_availability) / Decimal(max(1, len(availability))))
def _frontload(self, index):
"""Get front-load multiplier, used to weight prices of blobs in a
stream towards the front of the stream.
At index 0, returns 1.0
As index increases, return value approaches 2.0
@param index: blob position in stream
@return: front-load multiplier
"""
return Decimal(2.0) - (self.alpha ** index)