Memorize memory duration once a turn. #27441
Conversation
ZhilkinSerg
added
Code: Performance
| // Only check traits once a turn since this is called a huge number of times. | ||
| static time_point current_turn = calendar::before_time_starts; | ||
| static size_t current_max = 0; | ||
| if( current_turn != calendar::turn ) { |
There was a problem hiding this comment.
I understand the idea behind, but I don't get how it would work with current implementation as this conditional expression would always be true.
There was a problem hiding this comment.
Is it because of the static? It's kind of magical how it works.
static type varname = expression;
Is only evaluated the first time the function is invoked, after that varname has a persistent value.
There was a problem hiding this comment.
So this is like: initialize current_turn once with calendar::before_time_starts and current_max with 0 on first call to max_memorized_tiles, skip initialization on subsequent calls, right?
| return SEEX * SEEY * 800; // 200 overmap tiles | ||
| // Only check traits once a turn since this is called a huge number of times. | ||
| static time_point current_turn = calendar::before_time_starts; | ||
| static size_t current_max = 0; |
There was a problem hiding this comment.
I feel that it's unnecessary to make these static, and they would more logically be member variables. For example, when you save a game and load a different one, it's still using the state from the previous game. Which could (if you got very unlucky) cause that new game's player to forget a bunch of map memory.
There was a problem hiding this comment.
Ugh you're right, there is a tiny collision risk.
Summary
SUMMARY: NonePurpose of change
Memorize player memory extent once a turn instead of repeatedly calculating it every time we update the memory cache.
In profiling, this was previously taking up 0.78% of execution time when moving quickly. It scales with number of draw operations, so any rapid input would do the same. Now it takes up roughly no time.
Describe the solution
Memorize the calculated value the first time it is retrieved per turn and keep returning the same value until the turn changes.
Describe alternatives you've considered
A more general caching system for player attributes might be nice, but that also runs a risk of not being zero-cost like this one is, and it would certainty be more complicated.
Additional context
This method gets called once for each seen tile since that triggers re-memorization, which explains why such a cheap method appears in profiling at all.