MemHack (Memory Hack) refers to the strategy of storing a user's
Memory object in
global to skip the
JSON.parse() normally required at first-access of
Memory in a tick, thus saving CPU every tick. Note that the hack is exactly that: a hack. It relies on the underlying implementation of the API, not the published API itself, giving it the potential to become obsolete or broken in the future.
Memory Implementation[edit | edit source]
The way the
Memory object works is when first accessed in a game tick it is run though a
JSON.parse() which converts it to an object from its stored-as-a-string state, then after any changes have been made end-of-tick it is run though a
JSON.stringify() for storage. The user running the code pays for this parsing/stringifying with CPU: the larger the
Memory object, the more costly it is to process.
When Memory is parsed naturally, the parsed object is stored in
RawMemory._parsed. At the end of the tick (after your code ends), the engine serializes the value in
RawMemory._parsed into the database, for use in the next tick. The time taken for serialization is included in your CPU usage. You can read more about the
Memory object in Screep's official docs.
Operation[edit | edit source]
MemHack works by creating an object in
global to store the
Memory object when initializing the global (and needs to be rebuilt if global dies due to code push, global reset, ect). At the start of subsequent ticks (start of a user's main loop before any other
Memory related calls) deletes the 'normal'
Memory object and replaces it with the global version which due to global persisting between ticks does not need to be parsed. Then it sets
RawMemory._parsed to the current global MemHack obj as well, this insures changes are updated to the normal
Memory object, so that in the event of a global reset the
Memory object will still have the changes and, that the Memory watcher / console changing still work. It is important to note, that
RawMemory._parsed is not officially documented in the API however, it has been around and accessible for several years. It is possible for this strategy to become defunct in the future, should this be changed.
Risky Business[edit | edit source]
If you are not risk adverse or want additional savings, you can delete
RawMemory._parsed for a tick, preventing serialization for that tick. You can add a control structure using
Game.time % x === 0 to have it only serialize every 5, 10, etc ticks. The lower the gap between saves, the easier it would be to recover from the older copy of Memory serialized in the backend. This could lose data such as recent Market transactions, intelligence gathered from Observers, and other things.
Code Examples[edit | edit source]
There are a few places you can view examples of this code:
postCrafter - Screepers' Snippets