SolidJS•6mo ago

SOLVED: Non-Reactive Memo for Reactive Values?

I wish to perform a memoized calculation on demand rather than optimistically. Here we see createMemo running optimistically: https://playground.solidjs.com/anonymous/63165594-60fe-4ff2-966f-620574dd5761 Here i've solved the problem by manually tracking the dirty state and determining whether to recalc or just return at call time: https://playground.solidjs.com/anonymous/21a6530b-632c-46df-80d6-48ddd75ba665 I'm fine with this solution, but i just wanted to check that i'm not missing anything obvious

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6 Replies

haluOP•6mo ago

for better visibility, heres the function i created:

function memo<T>(watch: () => any, cb: () => T) {
  let last_val: T;

  let is_dirty = true;
  createComputed(() => {
    watch();
    console.log("made dirty");
    is_dirty = true;
  });

  return () => {
    if (is_dirty) {
      last_val = cb();
      is_dirty = false;
    }
    return last_val;
  };
}

function memo<T>(watch: () => any, cb: () => T) {
  let last_val: T;

  let is_dirty = true;
  createComputed(() => {
    watch();
    console.log("made dirty");
    is_dirty = true;
  });

  return () => {
    if (is_dirty) {
      last_val = cb();
      is_dirty = false;
    }
    return last_val;
  };
}

mdynnl•6mo ago

i think you’re looking for on.

const [track, trigger] = createSignal(void 0, { equals: false })
const value = createMemo(on(track, compute))

// …
trigger()

const [track, trigger] = createSignal(void 0, { equals: false })
const value = createMemo(on(track, compute))

// …
trigger()

bigmistqke•6mo ago

there is also https://primitives.solidjs.community/package/memo#createlazymemo

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A library of high-quality primitives that extend SolidJS reactivity

haluOP•6mo ago

oh cool! didn’t realize there was a deferred option in on() i’ll check these out after i wake up thx guys i misunderstood defer, doesn't really help here... found that lazyMemo doesn't really work with untrack https://playground.solidjs.com/anonymous/a7e1c35c-7687-44f7-bfa3-8530bed6a914 however, untrack is no longer be necessary given how it works (at least for my use-case) ~~https://playground.solidjs.com/anonymous/89072d00-f796-441b-ac99-4415d22f095e~~ https://playground.solidjs.com/anonymous/6851a2d5-d67f-42a3-894a-693c95838b1d couldn't get a track/trigger version to work as trigger is always dirty, thus the memo always computes regardless of whether signals in it callback are clean/unchanged:

function memo<T>(watch: ()=>any, cb: () => any) {
  const [track, trigger] = createSignal(void 0, { equals: false })
  const value = createMemo(on(track, cb, {defer:true}))
  return () => {
    trigger()
    return value();
  };
}

function memo<T>(watch: ()=>any, cb: () => any) {
  const [track, trigger] = createSignal(void 0, { equals: false })
  const value = createMemo(on(track, cb, {defer:true}))
  return () => {
    trigger()
    return value();
  };
}

thx for the help guys!

mdynnl•6mo ago

if i understood correctly here, you want to re-compute based on a set of dependencies and only when there are subscriptions? a combination of lazyMemo + on

haluOP•6mo ago

just lazyMemo was what i needed, using on/watch pattern just made it easier roll my own quickly (don't have to worry about first run tracking etc.) turns out lazyMemo primitive wasn't working in my production use-case... This is what i had to do to eliminate the watcher/on() pattern: https://playground.solidjs.com/anonymous/8dc85006-f489-46b1-887a-18d1f9c7812f

function memo<T>(cb: () => any) {
  /*
    The goal of this memo is to minimize recalculations, 
    yet still supply a syncronized value on demand.
    - The only way to minimize recalculation on demand in this scenario 
      is to track whether dependancies go dirty (recalc required).
    - Avoiding recalc on reactive updates means the
      subscriptions will be cleared and the effect disposed.
      This actually eliminates unnecesary side-effects entirely,
      but requires the effect be re-initialized each recalculation. 
  */
  let [last_val, set_last] = createSignal<T>();
  let is_dirty = true;

  let owner = getOwner();
  let effect = () => {
    runWithOwner(owner, () => {
      createComputed(() => {
        if (is_dirty) {
          console.log("recalc");
          // run, memo, and mark clean
          set_last(cb());
          is_dirty = false;
        } else {
          console.log("made dirty");
          // Dispose effect:
          // no need to listen to subsequent updates once known to be dirty
          is_dirty = true;
        }
      });
    });
  };
  effect();

  return () => {
    // if dirty, recalc on demand
    // init new comp. to listen for dirty toggle
    if (is_dirty) effect(); 
    return last_val();  // return clean memo
  };
}

function memo<T>(cb: () => any) {
  /*
    The goal of this memo is to minimize recalculations, 
    yet still supply a syncronized value on demand.
    - The only way to minimize recalculation on demand in this scenario 
      is to track whether dependancies go dirty (recalc required).
    - Avoiding recalc on reactive updates means the
      subscriptions will be cleared and the effect disposed.
      This actually eliminates unnecesary side-effects entirely,
      but requires the effect be re-initialized each recalculation. 
  */
  let [last_val, set_last] = createSignal<T>();
  let is_dirty = true;

  let owner = getOwner();
  let effect = () => {
    runWithOwner(owner, () => {
      createComputed(() => {
        if (is_dirty) {
          console.log("recalc");
          // run, memo, and mark clean
          set_last(cb());
          is_dirty = false;
        } else {
          console.log("made dirty");
          // Dispose effect:
          // no need to listen to subsequent updates once known to be dirty
          is_dirty = true;
        }
      });
    });
  };
  effect();

  return () => {
    // if dirty, recalc on demand
    // init new comp. to listen for dirty toggle
    if (is_dirty) effect(); 
    return last_val();  // return clean memo
  };
}

(did this mostly for fun, not sure I'd actually use it) tldr - effect runs twice to dispose itself and is recreated as necessary when recalculate on demand the neat thing is you can turn this into a lazyMemo (in the more traditional sense) by making is_dirty a signal ~~https://playground.solidjs.com/anonymous/9180d89f-9645-41b0-be79-a4c9a649b852~~ https://playground.solidjs.com/anonymous/0890796b-142f-4a88-b3be-2c4521ec4552 (had to pin deps) comparison to OG lazyMemo: ~~https://playground.solidjs.com/anonymous/f3e5d31e-56a0-463c-8754-914c6c3515c4~~ https://playground.solidjs.com/anonymous/16c504f7-3ffa-4532-b071-176bee23d9b9 ( had to pin deps )

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SOLVED: Non-Reactive Memo for Reactive Values?