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bancor.py
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bancor.py
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import numpy as np
class Reserve:
def __init__(self, name, amount, crr, verbose=0):
assert(amount > 0)
assert(crr > 0.0 and crr <= 1.0)
self.name = name
self.amount = amount
self.crr = crr
self.verbose = verbose
def __str__(self):
if self.verbose > 0:
return '[{}'.format(self.name) \
+ ' R={}'.format(np.round(self.amount, 3)) \
+ ' F={}]'.format(np.round(self.crr, 3))
else:
return ''
def log(self):
print(self)
class TokenChanger:
def __init__(self, name, supply, reserve_tokens=dict(), verbose=0, precision=4):
self.name = name
self.reserve_tokens = reserve_tokens
self.supply = supply
self.verbose=verbose
self.precision=precision
if self.verbose > 0:
self.log()
def log(self):
if self.verbose > 0:
print('[{}][LOG]'.format(self.name)
+ ' S={s} CRR={crr}:'.format(crr=np.round(self.crr, self.precision), s=np.round(self.supply, self.precision)) \
+ ':'.join([str(r) for _, r in self.reserve_tokens.items()])
)
def add_reserve(self, reserve):
assert(type(reserve) is Reserve)
assert(reserve.name not in self.reserve_tokens.keys())
self.reserve_tokens[reserve.name] = reserve
crr = self.crr
assert(crr >= 0 and crr <= 1.0)
@property
def crr(self):
return np.sum([r.crr for _, r in self.reserve_tokens.items()])
@property
def reserve(self):
reserve_tot = np.sum([r.amount for _,r in self.reserve_tokens.items()])
assert(reserve_tot >= 0)
return reserve_tot
@property
def price(self):
return self.reserve/(self.crr * self.supply)
def partial_prices(self):
return dict(zip(self.reserve_tokens.keys(),
[self.__partial_price(tkn) for tkn in self.reserve_tokens.keys()]))
def __partial_price(self, token, reserve_amount=None, supply=None):
"""
Implied price of the SmartToken if one buys it using the given token
:param token:
:param reserve_amount: if unset used the actual reserve amount otherwise this price is sim
:return:
"""
assert(token in self.reserve_tokens.keys())
reserve = self.reserve_tokens[token]
assert (type(reserve) is Reserve)
if reserve_amount is None:
reserve_amount = reserve.amount
if supply is None:
supply = self.supply
return reserve_amount / (reserve.crr * supply)
def buy(self, amount, from_token, const=False):
"""
Exchange amount of reserve token for SmartToken
:param amount: amount of reserve token to be sold
:param from_token: name of token being sold
:param const: set to True to get the answer without modifying the object
:return:
"""
assert(from_token in self.reserve_tokens.keys())
assert(amount >= 0)
reserve = self.reserve_tokens[from_token]
P0 = self.__partial_price(from_token)
R0 = reserve.amount
S0 = self.supply
R1 = R0 + amount
if not const:
self.reserve_tokens[from_token].amount = R1
S1 = S0 * np.power(R1/R0, reserve.crr) #update supply while maintaining crr
dS = S1 - S0
assert(dS >= 0)
if not const:
self.supply = S1
if self.verbose > 1:
self.log()
if self.verbose > 0:
px_eff = amount / dS
P1 = self.__partial_price(from_token, R1, S1)
slippage = 10000 * (px_eff / P0 - 1)
print('[{n}][BUY] {amt}[{ctr}] => {dS}[{n}] ; P0={P0} P1={P1} PAY={px} SLIP={slip}(bps)'.format(
amt=np.round(amount, self.precision), ctr=from_token,
dS=np.round(dS, self.precision), n=self.name,
P0=np.round(P0, self.precision), P1=np.round(P1, self.precision),
px=np.round(px_eff, self.precision), slip=np.round(slippage, self.precision)))
return dS
def sell(self, amount, to_token, const=False):
"""
Exchange SmartToken for a certain amount of reserve token
:param amount: amount of SmartToken to be sold
:param to_token: name of reserve token to be bought
:param const: set to True to get the answer without modifying the object
:return:
"""
assert(to_token in self.reserve_tokens.keys())
assert(amount >= 0 and amount <= self.supply)
reserve = self.reserve_tokens[to_token]
P0 = self.__partial_price(to_token)
R0 = reserve.amount
S0 = self.supply
S1 = S0 - amount
if not const:
self.supply = S1
R1 = R0 * np.power(S1/S0, 1/reserve.crr) #update reserve while maintaining crr
if not const:
self.reserve_tokens[to_token].amount = R1
dR = R0 - R1
assert(dR >= 0)
if self.verbose > 1:
self.log()
if self.verbose > 0:
px_eff = dR/amount
slippage = 10000*(1-px_eff/P0)
P1 = self.__partial_price(to_token, R1, S1)
print('[{n}][SELL] {amt}[{n}] => {dR}[{ctr}] ; P0={P0} P1={P1} REC={px} SLIP={slip}(bps)'.format(
amt=np.round(amount, self.precision), n=self.name,
ctr=to_token, dR=np.round(dR, self.precision),
P0=np.round(P0, self.precision), P1=np.round(P1, self.precision),
px=np.round(px_eff, self.precision), slip=np.round(slippage, self.precision)
))
return dR
def exchange(self, amount, from_token, to_token, const=False):
"""
Exchange between 2 reserve tokens using the SmartToken
:param amount: amount of base reserve token to be sold
:param from_token: name of base reserve token
:param to_token: name of target reserve token
:param const: set to True to get the answer without modifying the object
:return:
"""
if self.verbose > 0:
self.log()
P0 = self.exchange_price(from_token,to_token)
st_amount = self.buy(amount, from_token, const)
to_amount = self.sell(st_amount, to_token, const)
px_eff = amount/to_amount
slip = 10000*(px_eff/P0-1)
if self.verbose > 1:
self.log()
if self.verbose > 0:
print('[{n}][EXCH] {from_amt}[{from_token}] => {ctr_amt}[{ctr_token}] PAY={px} SLIP={slip}(bps)'.format(
n=self.name, from_amt=np.round(amount, self.precision),from_token=from_token,
ctr_amt=np.round(to_amount, self.precision),ctr_token=to_token,
px=np.round(px_eff, self.precision), slip=np.round(slip, self.precision)))
return to_amount
def exchange_price(self, from_token, to_token):
"""
Return the mid price for exchanging from_token => to_token
:param from_token:
:param to_token:
:return:
"""
if from_token == self.name:
return self.__partial_price(to_token)
elif to_token == self.name:
return 1/self.__partial_price(from_token)
assert (from_token in self.reserve_tokens.keys())
assert (to_token in self.reserve_tokens.keys())
base = self.reserve_tokens[from_token]
ctr = self.reserve_tokens[to_token]
px_imp = (base.amount*ctr.crr)/(ctr.amount*base.crr)
if self.verbose > 1:
self.log()
if self.verbose > 0:
print('[{n}][IMP] {ctr}/{base}={px}'.format(
n=self.name, ctr=to_token, base=from_token, px=np.round(px_imp, self.precision)
))
return px_imp
class SmartETF(TokenChanger):
def __init__(self, name, supply, reserve_tokens=dict(), verbose=0, precision=4):
TokenChanger.__init__(self, name, supply, reserve_tokens, verbose, precision)
@property
def index(self):
return dict(zip(self.reserve_tokens.keys(),[r.crr for r in list(self.reserve_tokens.values())]))
def creation(self, basket):
"""
convert a basket of reserve currencies into units of the SmartETF
:param basket:
:return: shares of the SmartETF
"""
assert(type(basket) is list)
bad_currencies = set(dict(basket).keys()).difference(self.reserve_tokens.keys())
if len(bad_currencies) != 0:
raise Exception('bad currencies in creation basket: {}'.format(bad_currencies))
shares = 0
for cmp in basket:
token = cmp[0]
amount = cmp[1]
# we do not allow const=False here because when sending a perfect basket
# it is crucial to modify the partial prices at each iteration in order to
# achieve the min slippage
shares += self.buy(amount=amount, from_token=token, const=False)
if self.verbose > 1:
print('[{n}][PARTIAL] {ppx}'.format(
n=self.name,
ppx=dround(self.partial_prices(), self.precision)
))
return shares
def redemption(self, shares):
"""
convert shares of the SmartETF into a basket of reserve currencies
:param shares:
:return:
"""
basket = dict()
ratio = (1-shares/self.supply)
for token in self.index.keys():
amount = self.supply*(1.0-np.power(ratio,self.index[token]))
basket[token] = self.sell(amount, token, const=False)
if self.verbose > 1:
print('[{n}][PARTIAL] {ppx}'.format(
n=self.name,
ppx=dround(self.partial_prices(), self.precision)
))
return basket
class SmartToken:
def __init__(self,name,R,S,F,verbose=0):
"""
Notations follow the document
Formulas for Bancor System by Meni Rosenfeld
"""
self.name = name
self.R = R
self.S = S
self.F = F
self.P = R/(S*F)
self.verbose=verbose
@property
def price(self):
return self.P
@property
def supply(self):
return self.S
@property
def reserve(self):
return self.R
def log(self):
if self.verbose > 0:
print('[{}]'.format(self.name)
+ ' R={}'.format(np.round(self.R,2))
+ ' S={}'.format(np.round(self.S,2))
+ ' F={}'.format(np.round(self.F,2))
+ ' P={}'.format(np.round(self.P,2)))
def exchange_cash(self,dR):
R0 = self.R
S0 = self.S
P0 = self.P
self.R += dR
scale = self.R/R0
self.S = S0*np.power(scale, self.F)
self.P = P0*np.power(scale, 1-self.F)
dS = self.S - S0
if self.verbose > 1:
print('[exchange_cash] dR={dR} scale={s} P0={P0} P1={P1}'.format(
dR=np.round(dR,2),
s=np.round(scale,2),
P0=np.round(P0,2),
P1=np.round(self.P,2)
))
self.log()
return dS
def exchange_shares(self,dS):
R0 = self.R
S0 = self.S
P0 = self.P
self.S += dS
scale = self.S/S0
self.R = R0*np.power(scale, 1/self.F)
self.P = P0*np.power(scale, 1/self.F-1)
dR = self.R - R0
self.log()
return -dR
def mkt_move(self,ret):
scale = 1 + ret
self.R *= scale
self.P *= scale
self.log()
class Portfolio:
def __init__(self,cash,token,verbose=0):
assert(cash >= 0)
self.shares = 0
self.cash = cash
self.token = token
self.verbose=verbose
self.log()
token.log()
def log(self):
if self.verbose > 0:
print('[portfolio] cash={}'.format(np.round(self.cash,2))
+ ' shares={}'.format(np.round(self.shares,2))
+ ' wealth={}'.format(np.round(self.wealth))
)
@property
def wealth(self):
return self.cash + self.shares*self.token.price
def buy(self,amount):
assert(amount >= 0)
assert(amount <= self.cash)
self.cash -= amount
self.shares += self.token.exchange_cash(amount)
self.log()
def sell(self,qty):
assert(qty >= 0)
assert(qty <= self.shares)
self.shares -= qty
self.cash += self.token.exchange_shares(-qty)
self.log()
def example1(verbose):
print('[EXAMPLE 1] buy then sell returns the wealth to initial level, so our intermediate wealth was "illusory"')
BNT = SmartToken('BNT',100.0,100.0,0.2,verbose)
pi = Portfolio(100.0,BNT,verbose)
pi.buy(100)
pi.sell(pi.shares)
return BNT
def example2(verbose):
print('[EXAMPLE 2] (consistency): we check that multiple small buys are equivalent to one large one')
BNT = SmartToken('BNT',100.0,100.0,0.2,verbose)
pi = Portfolio(100.0,BNT,verbose)
pi.buy(50)
pi.buy(50)
pi.sell(pi.shares)
return BNT
def example3(verbose):
print('[EXAMPLE 3] (consistency): we check that if we buy and the market moves meanwhile the result is consistent')
BNT = SmartToken('BNT',100.0,100.0,0.2,verbose)
pi = Portfolio(100.0,BNT,verbose)
pi.buy(50)
BNT.mkt_move(0.05) #market moves 5% up
pi.buy(50)
pi.sell(pi.shares)
np.testing.assert_almost_equal(pi.cash,102.5)
np.testing.assert_almost_equal(BNT.price,5.25)
return BNT
def example4(verbose):
print('[EXAMPLE 4] (exchange token): we show the slippage incurred by using an exchange token')
GNO = Reserve('GNO',amount=25000,crr=0.2,verbose=1)
GNO.log()
ETH = Reserve('ETH',amount=100000,crr=0.8,verbose=1)
ETH.log()
GNOETH=TokenChanger('GNOETH', reserve_tokens=dict(), supply=1000, verbose=1)
GNOETH.log()
GNOETH.add_reserve(GNO)
GNOETH.log()
GNOETH.add_reserve(ETH)
GNOETH.log()
P0 = GNOETH.exchange_price('GNO', 'ETH')
amt = GNOETH.exchange(10,'GNO', 'ETH')
P1 = GNOETH.exchange_price('GNO', 'ETH')
return GNOETH
def example5(verbose):
print('[EXAMPLE 5] where we show that for a basket token there is a cheapest reserve to buy the smart token')
GNO = Reserve('GNO',amount=25000, crr=0.2, verbose=1)
ETH = Reserve('ETH',amount=100000, crr=0.8, verbose=1)
GNOETH=TokenChanger('GNOETH', reserve_tokens=dict(GNO=GNO, ETH=ETH), supply=1000, verbose=1, precision=4)
print('all partial prices are equal:{}'.format(GNOETH.partial_prices()))
P0 = GNOETH.exchange_price('GNO','ETH')
amt = GNOETH.exchange(100,'GNO','ETH')
P1 = GNOETH.exchange_price('GNO','ETH')
print('Displayed SmartToken price: {}'.format(np.round(GNOETH.price, 4)))
print('now partial prices are different, SmartToken is cheaper in ETH!: {}'.format(GNOETH.partial_prices()))
print('proof:')
GNOETH.buy(100, 'ETH', const=True)
GNOETH.buy(100, 'GNO', const=True)
return GNOETH
def make_infra(verbose=0,infra_verbose=1):
if verbose:
print('data from coinmarketcap accurate as of 20170617 3am GMT, all amounts expressed in ETH')
mktcap = dict(RLC=152889.0, GNT=1394191.0, STORJ=136614.0, SC=1233871.0)
if verbose:
print('mktcaps: {}'.format(mktcap))
supply = dict(RLC=79070793, GNT=829252000, STORJ=51173144, SC=26994297972)
if verbose:
print('supplies: {}'.format(supply))
price = dict(zip(mktcap.keys(), [mktcap[k] / supply[k] for k in mktcap.keys()]))
if verbose:
print('prices: {}'.format(price))
tot_mktcap = np.sum(list(mktcap.values()))
if verbose:
print('total mktcap={}'.format(tot_mktcap))
idx_wgts = dict(zip(mktcap.keys(), [int(mc * 1.0 / tot_mktcap * 100000) / 100000 for _, mc in mktcap.items()]))
if verbose:
print('index weights are chosen to reflect the mktcap relative weight at the time we rebalance the index, which happens now')
print('index weights: {}'.format(idx_wgts))
print('we build INFRA assuming we use 1% of each mktcap as reserves and issue the corresponding supply of INFRA as tokens')
RLC = Reserve('RLC', mktcap['RLC'] / 100, idx_wgts['RLC'], 1)
GNT = Reserve('GNT', mktcap['GNT'] / 100, idx_wgts['GNT'], 1)
STORJ = Reserve('STORJ', mktcap['STORJ'] / 100, idx_wgts['STORJ'], 1)
SC = Reserve('SC', mktcap['SC'] / 100, idx_wgts['SC'], 1)
reserves = dict(RLC=RLC, GNT=GNT, STORJ=STORJ, SC=SC)
# an ethereum infrastructure ETF
INFRA = SmartETF('INFRA', reserve_tokens=reserves, supply=100000, verbose=infra_verbose)
if verbose:
print('INFRA price={}'.format(INFRA.price))
print('INFRA partial prices: {}'.format(INFRA.partial_prices()))
return INFRA
def make_bnt(verbose=0):
eth_raised = 396720
eth_reserve = eth_raised * 0.2
bnt_supply = 79323978.3607422567766216
ETH = Reserve('ETH', amount=eth_reserve, crr=0.1, verbose=1)
BNT = TokenChanger(name='BNT', supply=bnt_supply, reserve_tokens=dict(ETH=ETH), verbose=verbose, precision=5)
return BNT, eth_raised
def example6(verbose):
print('[EXAMPLE 6] where we build an infrastructure etf on the bancor protocole, called INFRA')
make_infra(verbose)
def example7(verbose):
print('[EXAMPLE 7] where we show that 23.2% of ETH raised during the Bancor ICO suffice to double the BNT price on monday')
BNT, eth_raised = make_bnt(verbose=verbose)
BNT.buy(0.232*eth_raised, 'ETH', const=True) # const=True allows not to modify the object
def dround(d,prec):
scale = 10**prec
return dict(zip(d.keys(),[int(v*scale)/scale for v in list(d.values())]))
def example8(verbose):
print('[EXAMPLE 8] a creation basket with the right proportions suffers a very very small slippage')
print('In this example we can exchange as much as 30% of the total reserve and incur less than 0.1bp of slippage')
print('pay CLOSE ATTENTION to the partial prices, at the end they are restored to the original levels')
INFRA = make_infra(verbose=0,infra_verbose=2)
print('[INFO] partial px: {}'.format(dround(INFRA.partial_prices(), 4)))
print('[INDEX] {}'.format(INFRA.index))
tgtshares = 30000
basket = [(k, tgtshares * v * INFRA.price) for k, v in INFRA.index.items()]
basket_value = np.sum([x[1] for x in basket])
print('[INFO] TGTSH={tgt} TGTVAL={tot} RESERVE={res} PERC={perc}%'.format(
tgt=tgtshares,
tot=np.round(basket_value, 4),
res=np.round(INFRA.reserve, 4),
perc=np.round(100.0 * basket_value / INFRA.reserve, 3)))
print('[INFO] BASKET: {}'.format(dround(dict(basket), 4)))
shares = INFRA.creation(basket=[basket[b] for b in [3, 2, 1, 0]])
INFRA.log()
print('[INFO] partial px: {}'.format(dround(INFRA.partial_prices(), 4)))
print('[RESULT] TGT={tgt} REC={rec} SLIP={slip}(bps)'.format(
tgt=tgtshares, rec=np.round(shares, 3), slip=np.round(10000 * (shares * 1.0 / tgtshares - 1), 3)))
def example9(verbose):
print('[EXAMPLE 9] a creation basket which is very imbalanced')
print('In this example we exchange only 3% of the total reserve by incur 22% slippage')
print('pay CLOSE ATTENTION to the partial prices, at the end they are very imbalanced')
INFRA = make_infra()
tgtshares = 3000
value = tgtshares * INFRA.price
print('TGT={tgt} VAL={val} RESERVE={res} PERC={perc}%'.format(
tgt=tgtshares,
val=np.round(value, 4),
res=np.round(INFRA.reserve, 4),
perc=np.round(value * 100.0 / INFRA.reserve, 4)
))
shares = INFRA.buy(tgtshares * INFRA.price, 'STORJ')
INFRA.log()
print('[INFO] partial px: {}'.format(dround(INFRA.partial_prices(), 4)))
print('[RESULT] TGT={tgt} REC={rec} SLIP={slip}(bps)'.format(
tgt=tgtshares, rec=np.round(shares, 3), slip=np.round(10000 * (shares * 1.0 / tgtshares - 1), 3)))
def example10(verbose):
print('[EXAMPLE 10] perfect redemption with no slippage')
INFRA = make_infra(infra_verbose=2)
P0 = INFRA.price
shares = 20000
basket = INFRA.redemption(shares)
P1 = INFRA.price
INFRA.log()
print('[INFO] P0={p0} P1={p1}'.format(p0=np.round(P0, 4),p1=np.round(P1, 4)))
print('[INFO] partial px: {}'.format(dround(INFRA.partial_prices(), 4)))
print('[INFO] basket:{}'.format(dround(basket, 3)))
rec = np.sum(list(basket.values()))
P_eff = rec/shares
print('[RESULT] P0={P0} SELL={tgt} REC={rec} SLIP={slip}(bps)'.format(
P0=np.round(P0,3), tgt=shares, rec=np.round(rec, 3),
slip=np.round(10000 * (1-P_eff / P0), 3)))
def main():
verbose=1
print('='*80)
example1(verbose)
print('='*80)
example2(verbose)
print('='*80)
example3(verbose)
print('='*80)
example4(verbose)
print('='*80)
example5(verbose)
print('='*80)
example6(verbose)
print('='*80)
example7(verbose)
print('='*80)
example8(verbose)
print('='*80)
example9(verbose)
print('='*80)
example10(verbose)
if __name__=='__main__':
main()