What are these shortwalls?
Is it something temporary?
The behavior for several versions has been to cancel short orders below the feed.
In 0.4.16, that is changing; short orders below the feed now execute at the feed.
You can view the feed as "pushing up" the price for all the shorts that fall below it, to the level of the feed. If a short is pushed up so far that the shorter's collateral is less than 1/2 (i.e. order.collateral < feed_price * order.quantity) then the short won't execute.
Before 0.4.16, short collateral was always price times quantity. Now, the shorter can optionally set collateral to be more than price times quantity. Why would the shorters want to do this? There are two incentives:
- A higher collateral short is able to be pushed up by the feed instead of being unable to execute when the feed tries to move up through it.
- When bidders try to buy through the short wall, the system prefers higher collateral shorts to execute first.
Here is the thread discussing these changes:
https://bitsharestalk.org/index.php?topic=9029.0EDIT, actually answering the question: The "short wall" I assume is the combination of all short orders below the feed, which the system has pushed up to the feed level via the above mechanism.
EDIT again: Change "cancelled" to "unable to execute" in the first of the two incentives.
Someone needs to write a clear explanation.