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DeFiPy

Swap-Deposit

To download notebook to this tutorial, see here

import os
import math
import numpy as np
from termcolor import colored
from uniswappy import *
user_nm = 'user0'
eth_amount = 1000
usdc_amount = 1000000

Problem Defined

Section titled “Problem Defined”
  • A SwapDeposit is where a certain amount of a specific token is deposited into the LP under one operation
  • Includes two steps:
    • (step 1) perform approx. 50% swap for opposing token
    • (step 2) using amt from step 1, perform 1:1 deposit
  • A portion of the incoming funds are swapped to achieve equal portions of both assets
  • These portions are then deposited into the LP
  • To ensure all the funds are deposited, we must determine the portion (α\alpha) of sins_{in} that must first get swapped
Δxsd=Δxswap+Δxdeposit\begin{equation} \Delta x_{sd} = \Delta x_{swap} + \Delta x_{deposit} \end{equation} Δxsd=αΔxsd+Δys(x+Δxsd)y−Δys\begin{equation} \Delta x_{sd} = \alpha \Delta x_{sd} + \frac{\Delta y_{s}(x+\Delta x_{sd})}{y - \Delta y_{s}} \end{equation}

Follows this system of equations:

Δys=997yαΔx1000x+997αΔx\begin{equation} \Delta y_{s} = \frac{997 y \alpha \Delta x }{1000x + 997\alpha\Delta x } \tag{Eq. 1} \end{equation} Δxsd=αΔxsd+Δys(x+αΔxsd)y−Δys\begin{equation} \Delta x_{sd} = \alpha\Delta x_{sd} + \frac{\Delta y_{s}(x + \alpha\Delta x_{sd} )}{y - \Delta y_{s}} \tag{Eq. 2} \end{equation}

where

  • Δxsd\Delta x_{sd} -> amt token in
  • Δys\Delta y_{s} -> amt opposing token out after swap
  • α\alpha -> portion of Δx\Delta x swapped in
  • x -> reserve0
  • y -> reserve1

Let’s highlight why the above considerations are important …

eth = ERC20("ETH", "0x09")
usdc = ERC20("USDC", "0x111")
exchg_data = UniswapExchangeData(tkn0 = eth, tkn1 = usdc, symbol="LP", address="0x011")


factory = UniswapFactory("ETH pool factory", "0x2")
lp = factory.deploy(exchg_data)
lp.add_liquidity(user_nm, eth_amount, usdc_amount, eth_amount, usdc_amount)


print('***\nInitial LP\n***')
lp.summary()


s_in = 100
alpha = 0.5
s_out = Swap().apply(lp, eth, user_nm, alpha*s_in)


print('***\nLP post step 1\n***')
lp.summary()


balance0 = alpha*s_in
balance1 = lp.quote(balance0, lp.reserve0, lp.reserve1)
lp.add_liquidity(user_nm, balance0, balance1, balance0, balance1)


print('***\nLP post step 2\n***')
lp.summary()




print('Given {} initial ETH:'.format(s_in))
print('  (step 1) {} ETH must first get swapped for {} '.format(alpha*s_in, s_out))
print('  (step 2) The received TKN gets deposited along with the remaining {} ETH'.format(balance0))


print('\nTotal deposited is {:.6f} + {:.6f} = {:.6f} ETH:'.format(alpha*s_in,  balance0, alpha*s_in + balance0))
print('However, we have {} unaccounted USDC which need to be considered when using a 50/50 split'.format(colored(str(usdc_amount-lp.get_reserve(usdc)), 'red', attrs=['bold'])))
*** Initial LP *** Exchange ETH-USDC (LP) Reserves: ETH = 1000.0, USDC = 1000000.0 Liquidity: 31622.776601683792 *** LP post step 1 *** Exchange ETH-USDC (LP) Reserves: ETH = 1050.0, USDC = 952517.026241844 Liquidity: 31622.776601683792 *** LP post step 2 *** Exchange ETH-USDC (LP) Reserves: ETH = 1100.0, USDC = 997874.9798724081 Liquidity: 33128.623106525876 Given 100 initial ETH: (step 1) 50.0 ETH must first get swapped for 47482.973758155924 (step 2) The received TKN gets deposited along with the remaining 50.0 ETH Total deposited is 50.000000 + 50.000000 = 100.000000 ETH: However, we have 2125.02012759191 unaccounted USDC which need to be considered when using a 50/50 split

Solve Problem

Section titled “Solve Problem”

Let’s now address this problem …

usdc = ERC20("TKN", "0x111")
eth = ERC20("ETH", "0x09")
exchg_data = UniswapExchangeData(tkn0 = eth, tkn1 = usdc, symbol="LP", address="0x011")


factory = UniswapFactory("ETH pool factory", "0x2")
lp = factory.deploy(exchg_data)
lp.add_liquidity(user_nm, eth_amount, usdc_amount, eth_amount, usdc_amount)


s_in = 100
alpha = 0.5
y = lp.get_reserve(usdc)
x = lp.get_reserve(eth)

Plug above into equation (1), and see how many TKN we get when 50% of ETH is swapped in for step (1)

s_out = (997*alpha*s_in*y)/(1000*x + 997*alpha*s_in)
print('For {} ETH, we get {:.2f} TKN with a 50% portion'.format(s_in, s_out))
For 100 ETH, we get 47482.97 TKN with a 50% portion

Now, lets check how many ETH gets SwapDeposited in when 50% of ETH is swapped in for step (1)

a1_out = alpha*s_in + s_out*(x + alpha*s_in)/(y - s_out)
print('Instead of {} ETH, we get {:.2f} ETH under a 50% portion'.format(s_in, a1_out))
Instead of 100 ETH, we get 102.34 ETH under a 50% portion

We can see that there is an imbalance in the system under a 50% distribution for step (1);

  • we need to solve the system above for α\alpha to get the proper distribution
  • plug (1) into (2) and we get:
Δx=αΔx+(997yαΔx1000x+997αΔx)(x+αΔxy−997yαΔx1000x+997αΔx)\begin{equation} \Delta x = \alpha\Delta x + \left(\frac{997 y\alpha\Delta x}{1000x + 997\alpha\Delta x} \right) \left(\frac{ x + \alpha\Delta x}{y - \frac{997 y \alpha \Delta x}{1000x + 997\alpha\Delta x}} \right) \end{equation}

reduces to:

α2997Δx21000x+α1997Δx1000−Δx=0\begin{equation} \alpha^2 \frac{997 \Delta x^2}{1000x} + \alpha\frac{1997\Delta x}{1000} - \Delta x = 0 \end{equation}

Now, solve for, and we can calculate the correct distribution using calc_deposit_dist

def calc_deposit_portion(lp, token_in, dx):


    tokens = lp.factory.token_from_exchange[lp.name]
    if(token_in.token_name == lp.token0):
        tkn_supply = lp.get_reserve(tokens[lp.token0])
    else:
        tkn_supply = lp.get_reserve(tokens[lp.token1])


    a = 997*(dx**2)/(1000*tkn_supply)
    b = dx*(1997/1000)
    c = -dx


    alpha = -(b - np.sqrt(b*b - 4*a*c)) / (2*a)
    return alpha
alpha = calc_deposit_portion(lp, eth, s_in)
print('The correct swap distrbution (for step 1) is {}'.format(alpha))
The correct swap distrbution (for step 1) is 0.4888217399419355

Now, check against our reduced quadratic, and we should expect to get 0

997*(alpha**2)*(s_in**2)/(1000*x) + alpha*s_in*(1997/1000) - s_in
-5.684341886080802e-14

Final Steps

Section titled “Final Steps”

Finally, lets run through the steps to a SwapDeposit and compare above

usdc = ERC20("USDC", "0x111")
eth = ERC20("ETH", "0x09")
exchg_data = UniswapExchangeData(tkn0 = eth, tkn1 = usdc, symbol="LP", address="0x011")


factory = UniswapFactory("ETH pool factory", "0x2")
lp = factory.deploy(exchg_data)
lp.add_liquidity(user_nm, eth_amount, usdc_amount, eth_amount, usdc_amount)


print('***\nInitial LP\n***')
lp.summary()


s_in = 100
alpha = calc_deposit_portion(lp, eth, s_in)
s_out = Swap().apply(lp, eth, user_nm, alpha*s_in)


print('***\nLP post step 1\n***')
lp.summary()


balance1 = s_out
balance0 = s_in-alpha*s_in
lp.add_liquidity(user_nm, balance0, balance1, balance0, balance1)


print('***\nLP post step 2\n***')
lp.summary()




print('Given {} initial ETH:'.format(s_in))
print('  (step 1) {} ETH must first get swapped for {} USDC'.format(alpha*s_in, s_out))
print('  (step 2) The received USDC gets deposited along with the remaining {} ETH'.format(balance0))


print('\nTotal deposited is {:.6f} + {:.6f} = {:.6f} ETH:'.format(alpha*s_in,  balance0, alpha*s_in + balance0))
*** Initial LP *** Exchange ETH-USDC (LP) Reserves: ETH = 1000.0, USDC = 1000000.0 Liquidity: 31622.776601683792 *** LP post step 1 *** Exchange ETH-USDC (LP) Reserves: ETH = 1048.8821739941936, USDC = 953529.2490856305 Liquidity: 31622.776601683792 *** LP post step 2 *** Exchange ETH-USDC (LP) Reserves: ETH = 1100.0, USDC = 1000000.0 Liquidity: 33163.92929950274 Given 100 initial ETH: (step 1) 48.88217399419355 ETH must first get swapped for 46470.75091436945 USDC (step 2) The received USDC gets deposited along with the remaining 51.11782600580645 ETH Total deposited is 48.882174 + 51.117826 = 100.000000 ETH:

Final Check

Section titled “Final Check”

Finally, let’s check when our solution is integrated into SwapDeposit

usdc = ERC20("USDC", "0x111")
eth = ERC20("ETH", "0x09")
exchg_data = UniswapExchangeData(tkn0 = eth, tkn1 = usdc, symbol="LP", address="0x011")


factory = UniswapFactory("ETH pool factory", "0x2")
lp = factory.deploy(exchg_data)
lp.add_liquidity(user_nm, eth_amount, usdc_amount, eth_amount, usdc_amount)
lp.summary()


s_in = 100
dep = SwapDeposit().apply(lp, eth, user_nm, s_in)
lp.summary()
Exchange ETH-USDC (LP) Reserves: ETH = 1000.0, USDC = 1000000.0 Liquidity: 31622.776601683792 Exchange ETH-USDC (LP) Reserves: ETH = 1100.0, USDC = 1000000.0 Liquidity: 33163.92929950274