BSIP 38: add target CR option to short positions

[abitmore]

1/3 for #51.

[oxarbitrage]

this looks good to me.

[TheTaconator]

[Edited to reflect corrections by @abitmore]

Interesting topic and very good BSIP. The guidance for UI/UX developers is very helpful. My suggestions are:

Math

As I understand the math, the target_CR variable is a dimensionless variable. (In contrast, a typical collateral ratio actually has implied dimensions of the collateral unit / debt unit). I suggest a sentence to clarify that the target_CR variable has no dimensions/units.

How to use the feature to address each of the rationales

If each of the rationales can be addressed with this new mechanism, it would be helpful to an end-user to know how to use it. If my understanding is correct, I think that they are as follows:

• some want to close their short positions completely to cut losses;

Set the target_CR to a very high value (maybe 6553.5%) or do not set the target_CR at all (which is the current default behavior)

• some want to sell as little collateral as possible to keep remaining short positions as large as possible;

Do not set the target_CR at all
Set the target_CR to as low as desirable (must be larger than the MCR)

• some want to sell more than minimum required collateral to reduce the possibility of being margin called again in the near future, but don't want to close their short positions completely.

Set the target_CR to a value larger than the MCR and less than maximum target_CR (6553.5%?)

[abitmore]

@TheTaconator thanks.

If I understood your question correctly, all collateral ratios in BitShares are dimensionless quantities.

About how to use the feature, it's easy to understand: selling collateral increases CR (collateral ratio). When you're margin called,

• if you don't have a target CR, then all your debt will be covered, maximum collateral will be sold;
• if you have a target, then some of your debt will be covered,
  • the higher your target is, more debt will be covered, so more collateral will be sold.

So,

• to cut loss, don't set target CR (same as current behavior), or set it to very high
• to keep as large position as possible, set target CR to as low as possible, the minimum allowed number is MCR
• otherwise, set target CR to a value some higher than MCR