Position Financial Cost Mechanism

Parameters:

Symbol	Meaning
$LIMIT_{s}$	soft limit ratio of total currencies’ open interests. Currently set at 0.7
$LIMIT_{h}$	hard limit ratio of total currencies’ open interests. Currently set at 0.9
$limit_{h}$	hard limit ratio of single currency’s open interest. Currently set at 1.1
pr	a risk management parameter for each currency. pr $\in (0,1)$
LP	total LP tokens’ net asset value, in USD, equal to LP’s cash after instantly closing all user positions without fee
$limit_{hard}$	hard limit of single currency’s open interest. $limit_{hard} = limit_h \times pr \times LP$
$LIMIT_{soft}$	soft limit of total currencies’ open interests. $LIMIT_{soft} = LIMIT_s\times LP$
$LIMIT_{hard}$	hard limit of total currencies’ open interests. $LIMIT_{hard} = LIMIT_h \times LP$

Symmetry sets soft limits and hard limits for total currencies’ open interests.

1). When $OI <= LIMIT_{soft}$, positions’ financing cost is 0.

2). When $OI > LIMIT_{soft}$, positions’ financing cost rate will be charged on each currency’s larger positions’ holders:

$$fc= min(1, \frac {|s| \cdot (OI-LIMIT_{soft})} { pr \cdot LP \cdot LIMIT_{hard}}) \cdot fc_{max}$$

Position financial costs will be credited to LP account to attract more LP.

Then when $OI >=\frac {pr \cdot LP \cdot LIMIT_{hard}} {|s|} + LIMIT_{soft}$, $fc = fc_{max}$

3). When $OI >= LIMIT_{hard}$ or $oi >= limit_{hard}$, each currency’s larger positions’ holders could only reduce positions, while the less positions’ holders could open new positions but not exceed larger positions.