Difference between revisions of "MemHack"

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memHack refers to the strategy of storing a user's <code>Memory</code> object in <code>global</code> to skip the <code>JSON.parse()</code> normally required at first-access of <code>Memory</code> in a tick.   
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MemHack refers to the strategy of storing a user's <code>Memory</code> object in <code>global</code> to skip the <code>JSON.parse()</code> normally required at first-access of <code>Memory</code> in a tick, thus saving [[CPU]] every tick.   
  
  
Normally, the way <code>Memory</code> works is when first accessed in a tick all of <code>Memory</code> is run though a <code>JSON.parse()</code> for the tick it is being used, then after any changes have been made end-of-tick it is run though <code>JSON.stringify()</code> for storage for the next tick it is accessed.  The user running their code pays for this parsing/stringifying with [[CPU]] the larger the <code>Memory</code> object the more costly it is to process. 
 
  
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The way the <code>Memory</code> object works is when first accessed in a game tick it is run though a <code>JSON.parse()</code>  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 <code>JSON.stringify()</code> for storage.  The user running the code pays for this parsing/stringifying with [[CPU]] the larger the <code>Memory</code> object the more costly it is to process.  You can read more about the <code>Memory</code> object in [https://docs.screeps.com/global-objects.html#Memory-object Screep's offical docs]. 
  
So, memHack works by creating an object to store <code>Memory</code> in global when global is 'first created' (and needs to be rebuilt if global dies due to code push, global reset, ect), then at the start of a tick (start of a user's main loop) deletes the 'normal' <code>Memory</code> object and replaces it with the global version which due to global persisting between ticks does not need to be parsed.  It finally sets the <code>RawMemory._parsed</code> to the current global memHack obj, this insures changes are updated to the normal <code>Memory</code> object, so that in the event of a global reset when reconstructing the <code>Memory</code> object will still have the changes and that the Memory watcher / console changing still work.  It is important to note, that <code>RawMemory._parsed</code> is not officially documented in the API however it has been around and accessible for several years.  It is possible for this method to become defunct in the future.
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So, MemHack works by creating an object in <code>global</code> to store the <code>Memory</code> object when initializing the global (and needs to be rebuilt if global dies due to code push, global reset, ect), then at the start of a tick (start of a user's main loop before any other <code>Memory</code> related calls) deletes the 'normal' <code>Memory</code> object and replaces it with the global version which due to global persisting between ticks does not need to be parsed.  Then it sets <code>RawMemory._parsed</code> to the current global MemHack obj as well, this insures changes are updated to the normal <code>Memory</code> object, so that in the event of a global reset the <code>Memory</code> object will still have the changes and, that the Memory watcher / console changing still work.  It is important to note, that <code>RawMemory._parsed</code> 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.
  
 
== Code Examples ==
 
== Code Examples ==

Revision as of 23:43, 29 March 2021

MemHack 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.


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. You can read more about the Memory object in Screep's offical docs.


So, 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), then at the start of a tick (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.

Code Examples

There are a few places you can view examples of this code:

postCrafter - Screepers' Snippets

ags131 - ZeSwarm

bencbartlett - OverMind