feat(providence): lfu and lru cache strategies for memoize

ing-bank · Dec 9, 2024 · 7e25f3e · 7e25f3e
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diff --git a/.changeset/blue-glasses-invite.md b/.changeset/blue-glasses-invite.md
@@ -0,0 +1,5 @@
+---
+'providence-analytics': patch
+---
+
+lfu and lru cache strategies for memoize
diff --git a/packages-node/providence-analytics/src/program/utils/memoize.js b/packages-node/providence-analytics/src/program/utils/memoize.js
@@ -1,6 +1,14 @@
 /**
- * For testing purposes, it is possible to disable caching.
+ * @typedef {{fn:MemoizedFn; count:number}} CacheStrategyItem
+ * @typedef {function & {clearCache: () => void}} MemoizedFn
  */
+
+/** @type {CacheStrategyItem[]} */
+let cacheStrategyItems = [];
+/** @type {'lfu'|'lru'} */
+let cacheStrategy = 'lfu';
+let limitForCacheStrategy = 100;
+/** For testing purposes, it is possible to disable caching. */
 let shouldCache = true;
 
 /**
@@ -22,11 +30,59 @@ function createCachableArg(arg) {
   }
 }
 
+function updateCacheStrategyItemsList() {
+  const hasReachedlimitForCacheStrategy = cacheStrategyItems.length >= limitForCacheStrategy;
+  if (!hasReachedlimitForCacheStrategy) return;
+
+  if (cacheStrategy === 'lfu') {
+    // eslint-disable-next-line no-case-declarations
+    const lowestCount = Math.min(...cacheStrategyItems.map(({ count }) => count));
+    const leastUsedIndex = cacheStrategyItems.findIndex(({ count }) => count === lowestCount);
+    const [itemToClear] = cacheStrategyItems.splice(leastUsedIndex, 1);
+    itemToClear?.fn.clearCache();
+    return;
+  }
+
+  // acheStrategy === 'lru'
+  const itemToClear = /** @type {CacheStrategyItem} */ (cacheStrategyItems.pop());
+  itemToClear?.fn.clearCache();
+}
+
+/**
+ * @param {MemoizedFn} newlyMemoizedFn
+ * @returns {CacheStrategyItem}
+ */
+function addCacheStrategyItem(newlyMemoizedFn) {
+  if (cacheStrategy === 'lfu') {
+    cacheStrategyItems.push({ fn: newlyMemoizedFn, count: 1 });
+    return cacheStrategyItems[cacheStrategyItems.length - 1];
+  }
+  // lru
+  cacheStrategyItems.unshift({ fn: newlyMemoizedFn, count: 1 });
+  return cacheStrategyItems[0];
+}
+/**
+ *
+ * @param {CacheStrategyItem} currentCacheStrategyItem
+ */
+function updateCacheStrategyItem(currentCacheStrategyItem) {
+  // eslint-disable-next-line no-param-reassign
+  currentCacheStrategyItem.count += 1;
+
+  if (cacheStrategy === 'lfu') return;
+
+  // 'lru': move recently used to top
+  cacheStrategyItems.splice(cacheStrategyItems.indexOf(currentCacheStrategyItem), 1);
+  cacheStrategyItems.unshift(currentCacheStrategyItem);
+}
+
 /**
  * @template T
  * @type {<T extends Function>(functionToMemoize:T, opts?:{ cacheStorage?:object; }) => T & {clearCache:() => void}}
  */
 export function memoize(functionToMemoize, { cacheStorage = {} } = {}) {
+  /** @type {CacheStrategyItem|undefined} */
+  let currentCacheStrategyItem;
   function memoizedFn() {
     // eslint-disable-next-line prefer-rest-params
     const args = [...arguments];
@@ -36,9 +92,17 @@ export function memoize(functionToMemoize, { cacheStorage = {} } = {}) {
     // Allow disabling of cache for testing purposes
     // @ts-expect-error
     if (shouldCache && cachableArgs in cacheStorage) {
+      updateCacheStrategyItem(/** @type {CacheStrategyItem} */ (currentCacheStrategyItem));
+
       // @ts-expect-error
       return cacheStorage[cachableArgs];
     }
+
+    if (!currentCacheStrategyItem) {
+      updateCacheStrategyItemsList();
+      currentCacheStrategyItem = addCacheStrategyItem(memoizedFn);
+    }
+
     // @ts-expect-error
     const outcome = functionToMemoize.apply(this, args);
     // @ts-expect-error
@@ -49,7 +113,9 @@ export function memoize(functionToMemoize, { cacheStorage = {} } = {}) {
   memoizedFn.clearCache = () => {
     // eslint-disable-next-line no-param-reassign
     cacheStorage = {};
+    currentCacheStrategyItem = undefined;
   };
+
   return /** @type {* & T & {clearCache:() => void}} */ (memoizedFn);
 }
 
@@ -66,10 +132,49 @@ memoize.disableCaching = () => {
  */
 memoize.restoreCaching = initialValue => {
   shouldCache = initialValue || true;
+  limitForCacheStrategy = 100;
+  cacheStrategyItems = [];
+  cacheStrategy = 'lfu';
 };
 
 Object.defineProperty(memoize, 'isCacheEnabled', {
   get() {
     return shouldCache;
   },
 });
+
+Object.defineProperty(memoize, 'limitForCacheStrategy', {
+  get() {
+    return limitForCacheStrategy;
+  },
+  set(/** @type {number} */ newValue) {
+    if (typeof newValue !== 'number') {
+      throw new Error('Please provide a number');
+    }
+    if (cacheStrategyItems.length) {
+      throw new Error('Please configure limitForCacheStrategy before using memoize');
+    }
+    limitForCacheStrategy = newValue;
+  },
+});
+
+Object.defineProperty(memoize, 'cacheStrategy', {
+  get() {
+    return cacheStrategy;
+  },
+  set(/** @type {'lfu'|'lru'} */ newStrategy) {
+    if (!['lfu', 'lru'].includes(newStrategy)) {
+      throw new Error("Please provide 'lfu' or 'lru'");
+    }
+    if (cacheStrategyItems.length) {
+      throw new Error('Please configure a strategy before using memoize');
+    }
+    cacheStrategy = newStrategy;
+  },
+});
+
+Object.defineProperty(memoize, 'cacheStrategyItems', {
+  get() {
+    return cacheStrategyItems;
+  },
+});
diff --git a/packages-node/providence-analytics/test-node/program/utils/memoize.test.js b/packages-node/providence-analytics/test-node/program/utils/memoize.test.js
@@ -1,5 +1,7 @@
 import { expect } from 'chai';
 import { it } from 'mocha';
+import sinon from 'sinon';
+
 import { memoize } from '../../../src/program/utils/memoize.js';
 
 describe('Memoize', () => {
@@ -341,5 +343,156 @@ describe('Memoize', () => {
       expect(sumMemoized('1', '2')).to.equal('12');
       expect(sumCalled).to.equal(2);
     });
+
+    describe('Strategies', () => {
+      beforeEach(() => {
+        memoize.restoreCaching();
+      });
+
+      describe('lfu (least frequently used) strategy', () => {
+        it('has lfu strategy by default', async () => {
+          expect(memoize.cacheStrategy).to.equal('lfu');
+        });
+
+        it('removes least used from cache', async () => {
+          memoize.limitForCacheStrategy = 2;
+
+          const spy1 = sinon.spy(() => {});
+          const spy2 = sinon.spy(() => {});
+          const spy3 = sinon.spy(() => {});
+
+          const spy1Memoized = memoize(spy1);
+          const spy2Memoized = memoize(spy2);
+          const spy3Memoized = memoize(spy3);
+
+          // Call spy1 3 times
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([{ fn: spy1Memoized, count: 1 }]);
+
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([{ fn: spy1Memoized, count: 2 }]);
+
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([{ fn: spy1Memoized, count: 3 }]);
+
+          // Call spy2 2 times (so it's the least frequently used)
+          spy2Memoized();
+          expect(spy2.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 },
+            { fn: spy2Memoized, count: 1 },
+          ]);
+
+          spy2Memoized();
+          expect(spy2.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 },
+            { fn: spy2Memoized, count: 2 },
+          ]);
+
+          // When we add number 3, we exceed limitForCacheStrategy
+          // This means that we 'free' the least frequently used (spy2)
+          spy3Memoized();
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 },
+            { fn: spy3Memoized, count: 1 },
+          ]);
+
+          spy2Memoized();
+          expect(spy2.callCount).to.equal(2);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 },
+            { fn: spy2Memoized, count: 1 }, // we start over
+          ]);
+
+          spy2Memoized(); // 2
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 }, // we start over
+            { fn: spy2Memoized, count: 2 },
+          ]);
+          spy2Memoized(); // 3
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 }, // we start over
+            { fn: spy2Memoized, count: 3 },
+          ]);
+          spy2Memoized(); // 4
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 3 }, // we start over
+            { fn: spy2Memoized, count: 4 },
+          ]);
+
+          console.debug('spy3Memoized');
+          spy3Memoized();
+          console.debug(memoize.cacheStrategyItems);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy2Memoized, count: 4 },
+            { fn: spy3Memoized, count: 1 }, // we start over
+          ]);
+        });
+      });
+
+      describe('lru (least recently used) strategy', () => {
+        it(`can set lru strategy"`, async () => {
+          memoize.cacheStrategy = 'lru';
+          expect(memoize.cacheStrategy).to.equal('lru');
+        });
+
+        it('removes least recently used from cache', async () => {
+          memoize.limitForCacheStrategy = 2;
+          memoize.cacheStrategy = 'lru';
+
+          const spy1 = sinon.spy(() => {});
+          const spy2 = sinon.spy(() => {});
+          const spy3 = sinon.spy(() => {});
+
+          const spy1Memoized = memoize(spy1);
+          const spy2Memoized = memoize(spy2);
+          const spy3Memoized = memoize(spy3);
+
+          // Call spy1 3 times
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([{ fn: spy1Memoized, count: 1 }]);
+
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([{ fn: spy1Memoized, count: 2 }]);
+
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([{ fn: spy1Memoized, count: 3 }]);
+
+          spy2Memoized();
+          expect(spy2.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy2Memoized, count: 1 },
+            { fn: spy1Memoized, count: 3 },
+          ]);
+
+          spy2Memoized();
+          expect(spy2.callCount).to.equal(1);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy2Memoized, count: 2 },
+            { fn: spy1Memoized, count: 3 },
+          ]);
+
+          spy3Memoized();
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy3Memoized, count: 1 },
+            { fn: spy2Memoized, count: 2 },
+          ]);
+
+          spy1Memoized();
+          expect(spy1.callCount).to.equal(2);
+          expect(memoize.cacheStrategyItems).to.deep.equal([
+            { fn: spy1Memoized, count: 1 }, // we start over
+            { fn: spy3Memoized, count: 1 },
+          ]);
+        });
+      });
+    });
   });
 });