Merge pull request #226 from Workiva/gha

Github Actions

.github/CODEOWNERS

@@ -0,0 +1 @@
+@Workiva/skreams

.github/workflows/tests.yaml

@@ -0,0 +1,38 @@
+name: "Tests"
+
+on:
+  pull_request:
+  push:
+    branches:
+      - 'master'
+    tags:
+      - '*'
+
+permissions:
+  pull-requests: write
+  contents: read
+  id-token: write
+
+jobs:
+  Tests:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go: [ '1.15', 'stable' ]
+    name: Tests on Go ${{ matrix.go }}
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v3.3.0
+        with:
+          path: go/src/github.com/Workiva/go-datastructures
+
+      - name: Setup Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: ${{ matrix.go }}
+
+      - name: Run Tests
+        timeout-minutes: 10
+        run: |
+          cd go/src/github.com/Workiva/go-datastructures
+          go test ./...

sort/sort.go

@@ -27,8 +27,11 @@ func MultithreadedSortComparators(comparators Comparators) Comparators {
 	var wg sync.WaitGroup
 
 	numCPU := int64(runtime.NumCPU())
-	if numCPU%2 == 1 { // single core machine
-		numCPU++
+	if numCPU == 1 { // single core machine
+		numCPU = 2
+	} else {
+		// otherwise this algo only works with a power of two
+		numCPU = int64(prevPowerOfTwo(uint64(numCPU)))
 	}
 
 	chunks := chunk(toBeSorted, numCPU)
@@ -70,3 +73,13 @@ func chunk(comparators Comparators, numParts int64) []Comparators {
 	}
 	return parts
 }
+
+func prevPowerOfTwo(x uint64) uint64 {
+	x = x | (x >> 1)
+	x = x | (x >> 2)
+	x = x | (x >> 4)
+	x = x | (x >> 8)
+	x = x | (x >> 16)
+	x = x | (x >> 32)
+	return x - (x >> 1)
+}