range-list: send nearest cursor for missing keys

Author: ignoramous

ds/range-list.js

@@ -98,8 +98,8 @@ export class RangeList {
   // get gets the value stored against an integer range (lo, hi)
   get(range) {
     const d = this.xget(range.lo, this.head);
-    if (d == null || d.value == null) return null;
-    return d.value;
+    if (d[0] == null || d[0].value == null) return null;
+    return d[0].value;
   }
 
   // search searches for key k, starting at cursor, cursornode
@@ -125,7 +125,8 @@ export class RangeList {
         // exclude tail, not a valid search result
         this.avgGetIter =
           this.avgGetIter > 0 ? Math.round((this.avgGetIter + c) / 2) : c;
-        return cur === this.tail ? null : cur;
+        // returns [ans-node, iter-position]
+        return cur === this.tail ? [null, cur] : [cur, cur];
       } else if (lt) {
         // for the next iteration, lookup siblings of cur
         node = cur;
@@ -137,11 +138,14 @@ export class RangeList {
       }
     }
 
-    return null;
+    // returns [ans-node, iter-position]
+    return [null, cur];
   }
 
   delete(range) {
-    const node = this.xget(range.lo, this.head);
+    const res = this.xget(range.lo, this.head);
+    const node = res[0];
+
     if (node == null) return false;
 
     // delete node from all its levels
@@ -227,14 +231,14 @@ export class RangeList {
 
   // selects level which is max way off from what is expected
   levelup() {
-    // max-diff between no. of nodes at expected at a level vs current
+    // max-diff between no. of nodes expected at a level vs current
     let maxdiff = 0;
     // level i where max-diff is
     let maxi = -1;
     // tracks total no. of nodes across levels, from higher levels to lower
     let sum = 0;
 
-    // levels are 1 indexed, the array is 0 index, that is,
+    // levels are 1 indexed, arrays are 0 indexed, that is,
     // level[0] => L1, level[1] => L2, level[7] => L8, and so on
     for (let i = this.levelhisto.length; i > 0; i--) {
       // number of nodes that level i
@@ -248,7 +252,7 @@ export class RangeList {
       }
       // a node which is on level[9] (L10) also exists at all other levels,
       // from 0..9 (L1..L10); that is, to get a count of nodes only on
-      // level[0] (L1) but not on other levels, substract out the sum of
+      // level[0] (L1) but not on other levels, subtract out the sum of
       // nodes on all other levels, 1..9 (L2..L10)
       sum += n;
     }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@serverless-dns/lfu-cache",
-  "version": "3.4.0",
+  "version": "3.4.1",
   "description": "Various LFU cache implementations",
   "main": "lfu.js",
   "type": "module",

strat/o1.js

@@ -91,16 +91,18 @@ export class O1 {
   // search searches for key k, starting at cursor it
   search(k, it, f = 1) {
     const cursor = it != null ? it.cursor : null;
-    const ans = this.store.search(k, cursor);
+    const res = this.store.search(k, cursor);
+    const ans = res[0];
+    const cur = res[1];
     if (ans) {
       const entry = ans.value;
       logd("search-hit; key:", k, "freq:", entry.freq);
       entry.freq += f;
       this.move(entry.freq, entry.node);
-      return mkcursor(ans, entry.value);
+      return mkcursor(cur, entry.value);
     }
     logd("search-miss", k);
-    return null;
+    return mkcursor(cur, null);
   }
 
   size() {

test/ds-perf.js

@@ -40,12 +40,14 @@ async function rangelistPerf(n) {
 
   const r = spacedinput(n);
 
+  // insert (range, value) pairs
   const ts1 = Date.now();
   r.forEach((i) => s.set(mkrange(i, i + 1), "r" + i));
   const ts2 = Date.now();
 
   console.log(tag, "setup duration", ts2 - ts1 + "ms");
 
+  // retrieve values of all valid keys
   const t = [];
   const miss = [];
   for (let i = 0; i < r.length; i++) {
@@ -60,7 +62,25 @@ async function rangelistPerf(n) {
   }
 
   console.log(tag, "get:avg(nodes-visited)", log2(n), "~=", s.avgGetIter);
+  s.avgGetIter = 0; // reset
 
+  // search nearby items, upto r.length no. of times
+  const tf = [];
+  const missf = [];
+  for (let j = 0, i = 0, x = null; j < r.length; j++) {
+    i = nearbyInt(i, 100, 0, n);
+
+    const t1 = Date.now();
+    x = s.search(mkrange(i, i), x)[1];
+    const t2 = Date.now();
+    tf.push(t2 - t1);
+
+    if (x == null) missf.push(i);
+  }
+
+  console.log(tag, "find:avg(nodes-visited)", log2(n), "~=", s.avgGetIter);
+
+  // delete all keys
   const td = [];
   const missd = [];
   for (let i = 0; i < r.length; i++) {
@@ -77,7 +97,7 @@ async function rangelistPerf(n) {
   logmissing(tag + " get:", miss);
   logmissing(tag + " del:", missd);
   logquantiles(tag, t, rlExpectedP99ForSize1M);
-  logsums(tag, t, td, rlExpectedSumForSize1M);
+  logsums(tag, t, tf, rlExpectedSumForSize1M);
 
   console.log(tag, "---fin---");
 
@@ -92,12 +112,14 @@ async function balancedRangeListPerf(n) {
 
   const r = spacedinput(n);
 
+  // insert (range, value) pairs
   const ts1 = Date.now();
   r.forEach((i) => s.set(mkrange(i, i + 1), "r" + i));
   const ts2 = Date.now();
 
   console.log(tag, "setup duration", ts2 - ts1 + "ms");
 
+  // balance rangelist
   const ts3 = Date.now();
   s = balancedCopy(s);
   const ts4 = Date.now();
@@ -128,7 +150,7 @@ async function balancedRangeListPerf(n) {
     i = nearbyInt(i, 100, 0, n);
 
     const t1 = Date.now();
-    x = s.search(mkrange(i, i), x);
+    x = s.search(mkrange(i, i), x)[1];
     const t2 = Date.now();
     tf.push(t2 - t1);
 
@@ -155,12 +177,14 @@ async function hashMapPerf(n) {
 
   const r = spacedinput(n);
 
+  // insert (k, v) pairs
   const ot1 = Date.now();
   r.forEach((i) => s.set(i, "m" + i));
   const ot2 = Date.now();
 
   console.log(tag, "setup duration", ot2 - ot1 + "ms");
 
+  // retrieve values of all valid keys
   const t = [];
   const miss = [];
   for (let i = 0; i < r.length; i++) {
@@ -174,6 +198,7 @@ async function hashMapPerf(n) {
     if (x == null) miss.push(i);
   }
 
+  // delete all keys
   const td = [];
   const missd = [];
   for (let i = 0; i < r.length; i++) {
@@ -254,7 +279,7 @@ function nearbyInt(i, jump, min, max) {
   const n = add ? i + vec : i - vec;
 
   if (n < min) return min + vec;
-  if (n > max) return max - vec;
+  if (n >= max) return max - vec;
   return n;
 }