Optimization in use_reducer

[Pascal-So]

Description

Yew currently provides two versions of the reducer hook:

• use_reducer: This hook always causes a re-render when an action is dispatched.
• use_reducer_eq: This hook avoids the re-render if the new state is the same as the old state. However, the state now has to implement PartialEq.

I feel like there is room for a middle ground: The reducer takes an Rc and returns an Rc. Even if we don't have a PartialEq implementation on the state, we can still know that the state must be unchanged if the reducer returns the exact same Rc back to us. This check is almost free (just a pointer comparison).

This PR adds a simple check if the two Rcs are the same, and in that case skip the re-render.

Note that even for use_reducer_eq this check is beneficial, since the PartialEq implementation might be more expensive than just a pointer comparison.

This change might be a breaking change if someone was relying on the exact number of re-renders, but I'd assume that this is not covered in Yew's semver guarantees, right?

Checklist

• I have reviewed my own code
• I have added tests

[github-actions]

Visit the preview URL for this PR (updated for commit b8538ba):

https://yew-rs-api--pr3945-use-reducer-optimiza-z0yvauva.web.app

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[github-actions]

Benchmark - core

Yew Master

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  3.945 ns      │ 4.08 ns       │ 3.947 ns      │ 3.951 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  4.018 ns      │ 4.381 ns      │ 4.02 ns       │ 4.025 ns      │ 100     │ 1000000000

[github-actions]

Benchmark - SSR

Yew Master

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	274.848	275.548	275.073	0.219
Hello World	10	445.426	457.397	449.457	3.592
Function Router	10	38742.516	39232.926	39002.762	170.422
Concurrent Task	10	1004.942	1006.867	1006.153	0.652
Many Providers	10	1017.577	1046.280	1031.017	7.837

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	281.701	282.900	281.942	0.373
Hello World	10	449.760	469.706	456.194	6.691
Function Router	10	32356.442	32962.141	32763.153	169.503
Concurrent Task	10	1005.229	1006.677	1006.016	0.513
Many Providers	10	1052.713	1095.280	1071.041	12.691

[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	100.197	100.197	0	0.000%
boids	168.080	168.080	0	0.000%
communication_child_to_parent	93.469	93.469	0	0.000%
communication_grandchild_with_grandparent	105.250	105.250	0	0.000%
communication_grandparent_to_grandchild	101.606	101.606	0	0.000%
communication_parent_to_child	90.900	90.900	0	0.000%
contexts	105.149	105.152	+0.003	+0.003%
counter	86.282	86.282	0	0.000%
counter_functional	88.272	88.275	+0.003	+0.003%
dyn_create_destroy_apps	90.321	90.321	0	0.000%
file_upload	99.346	99.346	0	0.000%
function_delayed_input	94.375	94.378	+0.003	+0.003%
function_memory_game	172.939	172.945	+0.006	+0.003%
function_router	405.547	405.590	+0.043	+0.011%
function_todomvc	164.148	164.162	+0.014	+0.008%
futures	235.159	235.159	0	0.000%
game_of_life	104.718	104.718	0	0.000%
immutable	255.868	255.871	+0.003	+0.001%
inner_html	80.803	80.803	0	0.000%
js_callback	109.374	109.377	+0.003	+0.003%
keyed_list	179.724	179.724	0	0.000%
mount_point	84.146	84.146	0	0.000%
nested_list	113.058	113.058	0	0.000%
node_refs	91.525	91.525	0	0.000%
password_strength	1728.826	1728.826	0	0.000%
portals	93.035	93.035	0	0.000%
router	376.134	376.140	+0.006	+0.002%
suspense	113.452	113.455	+0.003	+0.003%
timer	88.634	88.634	0	0.000%
timer_functional	98.875	98.880	+0.005	+0.005%
todomvc	142.088	142.088	0	0.000%
two_apps	86.146	86.146	0	0.000%
web_worker_fib	136.224	136.237	+0.014	+0.010%
web_worker_prime	187.438	187.466	+0.027	+0.015%
webgl	83.223	83.223	0	0.000%

✅ None of the examples has changed their size significantly.

[Madoshakalaka]

rebased onto master

since it's a breaking change, will probally release with yew 0.23

[Madoshakalaka]

I looked at the SSR benchmarks and Function Router is the only one that has use_reducer usage (5 distinct use_reducer/use_reducer_eq call sites across its components)

It does show a massive performance gain above (~39,000ms → ~32,700ms (20% faster) )

I think it's a solid improvement