Optimize PAC3 Event Parts: Reduce CPU Usage
PAC3 (Playermodel Animation Controller 3) is a powerful tool for customizing character models in games, allowing for intricate animations and effects. However, like any complex system, it can sometimes suffer from performance issues. One area that has been identified as a significant drain on CPU resources, particularly on a per-tick basis, is the event part's implementation of its OnThink() method. This article delves into the inefficiencies found within this component and proposes solutions to dramatically improve performance, leading to a smoother and more responsive experience for users.
The Bottleneck: OnThink() and Inefficient fix_args()
The core of the performance problem lies in how the event part handles its arguments. Specifically, the OnThink() method, which is called every single tick of the game loop, makes an expensive call to a function named fix_args(). This function, unfortunately, performs a lot of unnecessary or redundant work every time it's invoked. To illustrate the severity of this issue, let's examine the code snippet provided: https://github.com/CapsAdmin/pac3/blob/e40dfa546f05c0c3583fad690666574e37e854fe/lua/pac3/core/client/parts/event.lua#L3698-L3720. This indicates that a substantial amount of processing is being executed repeatedly, even when it might not be required.
The fix_args() function is designed to sanitize event arguments. While it has a valid use case when called during the SetEvent() process – ensuring that arguments are in a correct and usable format before being applied – its inclusion within OnThink() is highly questionable. The function's logic appears to be computationally intensive, and running it every tick is akin to a chef washing their hands after every single chop of a vegetable, regardless of whether they've touched anything else. This constant, unnecessary sanitization consumes valuable CPU cycles that could otherwise be allocated to more critical game processes, such as rendering, physics, or AI.
The concern here is not just about the inefficiency but also about potential design flaws. If event arguments can be modified externally in ways that necessitate a re-sanitization every tick, it points to a larger issue with how these arguments are managed. A more robust system would either prevent such modifications from occurring outside of controlled setters or ensure that sanitization is only performed when absolutely necessary. The current implementation creates a 'footgun' – a feature that is easy to misuse and leads to unintended negative consequences, in this case, severe performance degradation. The proposal to add an invalidation check, as demonstrated in the provided Lua snippet, offers a practical and effective solution. By only re-processing arguments when they have actually changed, fix_args() would be invoked far less frequently, directly translating to reduced CPU load. The reported ~15% reduction in outfit rendering time on outfits with numerous event parts is a strong testament to the impact of this optimization.
The Impact of Inefficient fix_args()
Let's delve deeper into why the repeated execution of fix_args() is such a significant performance drain within PAC3's event parts. The OnThink() function, as its name suggests, is designed to execute logic on every frame or 'tick' of the game. This is a critical part of game loops, responsible for updating game states, animations, and other dynamic elements. When a computationally expensive function like fix_args() is called within OnThink(), it means that this heavy processing load is being applied continuously. Imagine a painter having to repaint a small section of a canvas every time they blink – the overall progress would be incredibly slow, and the painter would be exhausted.
The nature of fix_args() likely involves iterating through argument data, performing data type checks, potentially converting values, or even complex string manipulations. Each of these operations, when performed on potentially large or numerous arguments, consumes CPU cycles. When this happens fifty times per second (a common tick rate), the cumulative effect can be substantial. For users with multiple PAC3 outfits, each potentially containing several event parts, this inefficiency can quickly add up, leading to noticeable lag, stuttering, and a general decrease in game performance. This is especially frustrating because the user is experiencing slowdowns not due to demanding graphics or complex game logic, but due to inefficient code within a customization tool.
The proposed solution, involving an invalidation check (if (self.Arguments == self.LastFixedArguments) then return end), is elegant in its simplicity and effectiveness. It introduces a state-tracking mechanism. LastFixedArguments acts as a memory of the arguments that were last processed and deemed valid. Before fix_args() proceeds with its expensive operations, it checks if the current self.Arguments are identical to self.LastFixedArguments. If they are the same, it means the arguments haven't changed since the last time they were fixed, and therefore, the expensive sanitization process can be skipped entirely for that tick. This prevents redundant work and ensures that fix_args() is only executed when there's an actual need to re-sanitize the arguments. The dramatic ~15% reduction in outfit rendering time observed by the user is a clear indicator that fix_args() was indeed performing a lot of work that was often unnecessary on a per-tick basis. This optimization directly addresses the 'wasting CPU per tick' issue by making the execution of fix_args() conditional on actual data changes, rather than continuous.
The Widespread Impact of Event and Proxy Parts
Beyond the specific implementation of fix_args() within event parts, it's crucial to understand the broader context of where these inefficiencies have the most impact. The article highlights that event and proxy parts are
