From 9f7e1f1cb04e2ab93799ab33c9ab5bebbd09eb88 Mon Sep 17 00:00:00 2001
From: Bruce Martin <bruce@chanzuckerberg.com>
Date: Wed, 7 Nov 2018 13:35:00 -0800
Subject: [PATCH] use quicksort instead of default system sort (#413)

---
 .../util/typedCrossfilter/sort.test.js        |  56 ++++++++++
 client/src/util/typedCrossfilter/sort.js      | 100 ++++++++++++++++++
 client/src/util/typedCrossfilter/util.js      |   4 +-
 3 files changed, 159 insertions(+), 1 deletion(-)
 create mode 100644 client/__tests__/util/typedCrossfilter/sort.test.js
 create mode 100644 client/src/util/typedCrossfilter/sort.js

diff --git a/client/__tests__/util/typedCrossfilter/sort.test.js b/client/__tests__/util/typedCrossfilter/sort.test.js
new file mode 100644
index 00000000..71ce948e
--- /dev/null
+++ b/client/__tests__/util/typedCrossfilter/sort.test.js
@@ -0,0 +1,56 @@
+import { sort, sortIndex } from "../../../src/util/typedCrossfilter/sort";
+
+function fillRange(arr, start = 0) {
+  const larr = arr;
+  for (let i = 0, len = larr.length; i < len; i += 1) {
+    larr[i] = i + start;
+  }
+  return larr;
+}
+
+function fillRand(arr) {
+  for (let i = 0, len = arr.length; i < len; i += 1) {
+    arr[i] = Math.random();
+  }
+  return arr;
+}
+
+describe("sort", () => {
+  [Array, Float32Array, Uint32Array, Int32Array, Float64Array].map(Type =>
+    test(Type.name, () => {
+      expect(sort(Type.from([6, 5, 4, 3, 2, 1, 0]))).toMatchObject(
+        Type.from([0, 1, 2, 3, 4, 5, 6])
+      );
+      expect(sort(Type.from([6, 5, 4, 3, 2, 1]))).toMatchObject(
+        Type.from([1, 2, 3, 4, 5, 6])
+      );
+
+      const source = fillRand(new Type(1000));
+      expect(sort(Type.from(source))).toMatchObject(Type.from(source).sort());
+    })
+  );
+});
+
+describe("sortIndex", () => {
+  [Array, Float32Array, Uint32Array, Int32Array, Float64Array].map(Type =>
+    test(Type.name, () => {
+      const source1 = Type.from([6, 5, 4, 3, 2, 1, 0]);
+      const index1 = fillRange(new Uint32Array(source1.length));
+      expect(sortIndex(index1, source1)).toMatchObject(
+        index1.sort((a, b) => source1[a] - source1[b])
+      );
+
+      const source2 = Type.from([6, 5, 4, 3, 2, 1]);
+      const index2 = fillRange(new Uint32Array(source2.length));
+      expect(sortIndex(index2, source2)).toMatchObject(
+        index2.sort((a, b) => source1[a] - source1[b])
+      );
+
+      const source3 = fillRand(new Type(1000));
+      const index3 = fillRange(new Uint32Array(source3.length));
+      expect(sortIndex(index3, source3)).toMatchObject(
+        index3.sort((a, b) => source1[a] - source1[b])
+      );
+    })
+  );
+});
diff --git a/client/src/util/typedCrossfilter/sort.js b/client/src/util/typedCrossfilter/sort.js
new file mode 100644
index 00000000..08fb3ec4
--- /dev/null
+++ b/client/src/util/typedCrossfilter/sort.js
@@ -0,0 +1,100 @@
+const SmallArray = 32;
+
+function insertionsort(a, lo, hi) {
+  for (let i = lo + 1; i < hi + 1; i += 1) {
+    const x = a[i];
+    let j;
+    for (j = i; j > lo && a[j - 1] > x; j -= 1) {
+      a[j] = a[j - 1];
+    }
+    a[j] = x;
+  }
+  return a;
+}
+
+function insertionsortIndirect(a, s, lo, hi) {
+  for (let i = lo + 1; i < hi + 1; i += 1) {
+    const x = a[i];
+    const t = s[x];
+    let j;
+    for (j = i; j > lo && s[a[j - 1]] > t; j -= 1) {
+      a[j] = a[j - 1];
+    }
+    a[j] = x;
+  }
+  return a;
+}
+
+function quicksort(a, lo, hi) {
+  if (hi - lo < SmallArray) {
+    return insertionsort(a, lo, hi);
+  }
+  if (lo < hi) {
+    // partition
+    const mid = Math.floor((lo + hi) / 2);
+    const p = a[mid];
+    let i = lo - 1;
+    let j = hi + 1;
+    while (i < j) {
+      do {
+        i += 1;
+      } while (a[i] < p);
+      do {
+        j -= 1;
+      } while (a[j] > p);
+      if (i < j) {
+        const tmp = a[i];
+        a[i] = a[j];
+        a[j] = tmp;
+      }
+    }
+    // sort
+    quicksort(a, lo, j);
+    quicksort(a, j + 1, hi);
+  }
+  return a;
+}
+
+function quicksortIndirect(a, s, lo, hi) {
+  if (hi - lo < SmallArray) {
+    return insertionsortIndirect(a, s, lo, hi);
+  }
+  if (lo < hi) {
+    // partition
+    const mid = Math.floor((lo + hi) / 2);
+    const p = a[mid];
+    const t = s[p];
+    let i = lo - 1;
+    let j = hi + 1;
+    while (i < j) {
+      do {
+        i += 1;
+      } while (s[a[i]] < t);
+      do {
+        j -= 1;
+      } while (s[a[j]] > t);
+      if (i < j) {
+        const tmp = a[i];
+        a[i] = a[j];
+        a[j] = tmp;
+      }
+    }
+    // sort
+    quicksortIndirect(a, s, lo, j);
+    quicksortIndirect(a, s, j + 1, hi);
+  }
+  return a;
+}
+
+// Convenience wrappers
+export function sort(arr, comparator = undefined) {
+  if (comparator !== undefined) {
+    // XXX for now
+    return arr.sort(arr, comparator);
+  }
+  return quicksort(arr, 0, arr.length - 1);
+}
+
+export function sortIndex(index, source) {
+  return quicksortIndirect(index, source, 0, index.length - 1);
+}
diff --git a/client/src/util/typedCrossfilter/util.js b/client/src/util/typedCrossfilter/util.js
index 108f1923..1aacafc0 100644
--- a/client/src/util/typedCrossfilter/util.js
+++ b/client/src/util/typedCrossfilter/util.js
@@ -1,6 +1,8 @@
 // jshint esversion: 6
 /* eslint no-bitwise: "off" */
 
+import { sortIndex } from "./sort";
+
 /*
     Utility functions, private to this module.
 */
@@ -31,7 +33,7 @@ export function sliceByIndex(src, index) {
 
 export function makeSortIndex(src) {
   const index = fillRange(new Uint32Array(src.length));
-  index.sort((a, b) => src[a] - src[b]);
+  sortIndex(index, src);
   return index;
 }