51 lines
1.9 KiB
Python
51 lines
1.9 KiB
Python
from zope.interface import implementer
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from decimal import Decimal
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from lbrynet.interfaces import IBlobPriceModel
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from lbrynet.conf import settings
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def get_default_price_model(blob_tracker, base_price, **kwargs):
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return MeanAvailabilityWeightedPrice(blob_tracker, base_price, **kwargs)
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class MeanAvailabilityWeightedPrice(object):
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"""
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Calculate mean-blob-availability and stream-position weighted price for a blob
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Attributes:
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base_price (float): base price
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alpha (float): constant, > 0.0 and <= 1.0, used to more highly value blobs at the beginning of a stream.
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alpha defaults to 1.0, which has a null effect
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blob_tracker (BlobAvailabilityTracker): blob availability tracker
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"""
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implementer(IBlobPriceModel)
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def __init__(self, tracker, base_price=settings.data_rate, alpha=1.0):
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self.blob_tracker = tracker
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self.base_price = Decimal(base_price)
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self.alpha = Decimal(alpha)
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def calculate_price(self, blob):
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mean_availability = self.blob_tracker.last_mean_availability
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availability = self.blob_tracker.availability.get(blob, [])
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index = 0 # blob.index
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price = self.base_price * self._get_availability_multiplier(mean_availability, availability) / self._frontload(index)
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return round(price, 5)
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def _get_availability_multiplier(self, mean_availability, availability):
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return Decimal(max(1, mean_availability) / Decimal(max(1, len(availability))))
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def _frontload(self, index):
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"""
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Get front-load multiplier, used to weight prices of blobs in a stream towards the front of the stream.
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At index 0, returns 1.0
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As index increases, return value approaches 2.0
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@param index: blob position in stream
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@return: front-load multiplier
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"""
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return Decimal(2.0) - (self.alpha ** index)
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