Go implementation by AlexanderYastrebov (#298)

* Go implementation by AlexanderYastrebov

This is a proof-of-concept to demonstrate non-java submission.
It requires Docker with BuildKit plugin to build and export binary.

Updates
* #67
* #253

* Use collision-free id lookup

* Use number of buckets greater than max number of keys

5 files changed, 452 insertions, 0 deletions

diff --git a/src/main/go/AlexanderYastrebov/Dockerfile b/src/main/go/AlexanderYastrebov/Dockerfile
new file mode 100644
index 0000000..a3b2806
--- /dev/null
+++ b/src/main/go/AlexanderYastrebov/Dockerfile
@@ -0,0 +1,22 @@
+#
+#  Copyright 2023 The original authors
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+FROM golang AS build-stage
+COPY . src/
+RUN cd src && go build .
+
+FROM scratch AS export-stage
+COPY --from=build-stage /go/src/1brc /
diff --git a/src/main/go/AlexanderYastrebov/README.md b/src/main/go/AlexanderYastrebov/README.md
new file mode 100644
index 0000000..dc01192
--- /dev/null
+++ b/src/main/go/AlexanderYastrebov/README.md
@@ -0,0 +1,58 @@
+# 1brc in go
+
+It uses Docker with BuildKit plugin to build and [export binary](https://docs.docker.com/engine/reference/commandline/build/#output) binary,
+see [prepare_AlexanderYastrebov.sh](../../../../prepare_AlexanderYastrebov.sh)
+and [calculate_average_AlexanderYastrebov.sh](../../../../calculate_average_AlexanderYastrebov.sh).
+
+Demo:
+```sh
+$ ./test.sh AlexanderYastrebov
+[+] Building 0.2s (9/9) FINISHED
+ => [internal] load .dockerignore                                                                                                             0.0s
+ => => transferring context: 2B                                                                                                               0.0s
+ => [internal] load build definition from Dockerfile                                                                                          0.0s
+ => => transferring dockerfile: 172B                                                                                                          0.0s
+ => [internal] load metadata for docker.io/library/golang:latest                                                                              0.0s
+ => [internal] load build context                                                                                                             0.0s
+ => => transferring context: 145B                                                                                                             0.0s
+ => [build-stage 1/3] FROM docker.io/library/golang                                                                                           0.0s
+ => CACHED [build-stage 2/3] COPY . src/                                                                                                      0.0s
+ => CACHED [build-stage 3/3] RUN cd src && go build .                                                                                         0.0s
+ => CACHED [export-stage 1/1] COPY --from=build-stage /go/src/1brc /                                                                          0.0s
+ => exporting to client directory                                                                                                             0.1s
+ => => copying files 2.03MB                                                                                                                   0.0s
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-10000-unique-keys.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-10.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-1.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-20.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-2.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-3.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-boundaries.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-complex-utf8.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-dot.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-shortest.txt
+Validating calculate_average_AlexanderYastrebov.sh -- src/test/resources/samples/measurements-short.txt
+
+# Run once to setup the benchmark
+# ./create_measurements.sh 1000000000
+# mv measurements.txt measurements_1B.txt
+# ln -s measurements_1B.txt measurements.txt
+# ./calculate_average_baseline.sh > out_expected.txt
+
+$ wc -l measurements_1B.txt
+1000000000 measurements_1B.txt
+
+$ ./evaluate2.sh AlexanderYastrebov royvanrijn
+...                                                                                                                                         0.0s
+Benchmark 1: ./calculate_average_AlexanderYastrebov.sh 2>&1
+  Time (mean ± σ):     16.786 s ±  0.545 s    [User: 56.030 s, System: 10.068 s]
+  Range (min … max):   15.918 s … 17.309 s    5 runs
+...
+Benchmark 1: ./calculate_average_royvanrijn.sh 2>&1
+  Time (mean ± σ):     16.731 s ±  0.190 s    [User: 56.485 s, System: 10.279 s]
+  Range (min … max):   16.490 s … 16.951 s    5 runs
+
+Summary
+  AlexanderYastrebov: trimmed mean 16.901712789513336, raw times 16.69836470718,17.30911065018,16.83413600418,15.91787706218,17.17263765718
+  royvanrijn: trimmed mean 16.738037123633333, raw times 16.4900939703,16.9513459953,16.5794539913,16.8297746273,16.8048827523
+```
diff --git a/src/main/go/AlexanderYastrebov/calc.go b/src/main/go/AlexanderYastrebov/calc.go
new file mode 100644
index 0000000..149d38d
--- /dev/null
+++ b/src/main/go/AlexanderYastrebov/calc.go
@@ -0,0 +1,283 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"runtime"
+	"sort"
+	"sync"
+	"syscall"
+)
+
+type measurement struct {
+	min, max, sum, count int64
+}
+
+func main() {
+	if len(os.Args) != 2 {
+		log.Fatalf("Missing measurements filename")
+	}
+
+	measurements := processFile(os.Args[1])
+
+	ids := make([]string, 0, len(measurements))
+	for id := range measurements {
+		ids = append(ids, id)
+	}
+	sort.Strings(ids)
+
+	fmt.Print("{")
+	for i, id := range ids {
+		if i > 0 {
+			fmt.Print(", ")
+		}
+		m := measurements[id]
+		fmt.Printf("%s=%.1f/%.1f/%.1f", id, round(float64(m.min)/10.0), round(float64(m.sum)/10.0/float64(m.count)), round(float64(m.max)/10.0))
+	}
+	fmt.Println("}")
+}
+
+func processFile(filename string) map[string]*measurement {
+	f, err := os.Open(filename)
+	if err != nil {
+		log.Fatalf("Open: %v", err)
+	}
+	defer f.Close()
+
+	fi, err := f.Stat()
+	if err != nil {
+		log.Fatalf("Stat: %v", err)
+	}
+
+	size := fi.Size()
+	if size <= 0 || size != int64(int(size)) {
+		log.Fatalf("Invalid file size: %d", size)
+	}
+
+	data, err := syscall.Mmap(int(f.Fd()), 0, int(size), syscall.PROT_READ, syscall.MAP_SHARED)
+	if err != nil {
+		log.Fatalf("Mmap: %v", err)
+	}
+
+	defer func() {
+		if err := syscall.Munmap(data); err != nil {
+			log.Fatalf("Munmap: %v", err)
+		}
+	}()
+
+	return process(data)
+}
+
+func process(data []byte) map[string]*measurement {
+	nChunks := runtime.NumCPU()
+
+	chunkSize := len(data) / nChunks
+	if chunkSize == 0 {
+		chunkSize = len(data)
+	}
+
+	chunks := make([]int, 0, nChunks)
+	offset := 0
+	for offset < len(data) {
+		offset += chunkSize
+		if offset >= len(data) {
+			chunks = append(chunks, len(data))
+			break
+		}
+
+		nlPos := bytes.IndexByte(data[offset:], '\n')
+		if nlPos == -1 {
+			chunks = append(chunks, len(data))
+			break
+		} else {
+			offset += nlPos + 1
+			chunks = append(chunks, offset)
+		}
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(len(chunks))
+
+	results := make([]map[string]*measurement, len(chunks))
+	start := 0
+	for i, chunk := range chunks {
+		go func(data []byte, i int) {
+			results[i] = processChunk(data)
+			wg.Done()
+		}(data[start:chunk], i)
+		start = chunk
+	}
+	wg.Wait()
+
+	measurements := make(map[string]*measurement)
+	for _, r := range results {
+		for id, rm := range r {
+			m := measurements[id]
+			if m == nil {
+				measurements[id] = rm
+			} else {
+				m.min = min(m.min, rm.min)
+				m.max = max(m.max, rm.max)
+				m.sum += rm.sum
+				m.count += rm.count
+			}
+		}
+	}
+	return measurements
+}
+
+func processChunk(data []byte) map[string]*measurement {
+	// Use fixed size linear probe lookup table
+	const (
+		// use power of 2 for fast modulo calculation,
+		// should be larger than max number of keys which is 10_000
+		entriesSize = 1 << 14
+
+		// use FNV-1a hash
+		fnv1aOffset64 = 14695981039346656037
+		fnv1aPrime64  = 1099511628211
+	)
+
+	type entry struct {
+		m     measurement
+		hash  uint64
+		vlen  int
+		value [128]byte // use power of 2 > 100 for alignment
+	}
+	entries := make([]entry, entriesSize)
+	entriesCount := 0
+
+	// keep short and inlinable
+	getMeasurement := func(hash uint64, value []byte) *measurement {
+		i := hash & uint64(entriesSize-1)
+		entry := &entries[i]
+
+		// bytes.Equal could be commented to speedup assuming no hash collisions
+		for entry.vlen > 0 && !(entry.hash == hash && bytes.Equal(entry.value[:entry.vlen], value)) {
+			i = (i + 1) & uint64(entriesSize-1)
+			entry = &entries[i]
+		}
+
+		if entry.vlen == 0 {
+			entry.hash = hash
+			entry.vlen = copy(entry.value[:], value)
+			entriesCount++
+		}
+		return &entry.m
+	}
+
+	// assume valid input
+	for len(data) > 0 {
+
+		idHash := uint64(fnv1aOffset64)
+		semiPos := 0
+		for i, b := range data {
+			if b == ';' {
+				semiPos = i
+				break
+			}
+
+			// calculate FNV-1a hash
+			idHash ^= uint64(b)
+			idHash *= fnv1aPrime64
+		}
+
+		idData := data[:semiPos]
+
+		data = data[semiPos+1:]
+
+		var temp int64
+		// parseNumber
+		{
+			negative := data[0] == '-'
+			if negative {
+				data = data[1:]
+			}
+
+			_ = data[3]
+			if data[1] == '.' {
+				// 1.2\n
+				temp = int64(data[0])*10 + int64(data[2]) - '0'*(10+1)
+				data = data[4:]
+				// 12.3\n
+			} else {
+				_ = data[4]
+				temp = int64(data[0])*100 + int64(data[1])*10 + int64(data[3]) - '0'*(100+10+1)
+				data = data[5:]
+			}
+
+			if negative {
+				temp = -temp
+			}
+		}
+
+		m := getMeasurement(idHash, idData)
+		if m.count == 0 {
+			m.min = temp
+			m.max = temp
+			m.sum = temp
+			m.count = 1
+		} else {
+			m.min = min(m.min, temp)
+			m.max = max(m.max, temp)
+			m.sum += temp
+			m.count++
+		}
+	}
+
+	result := make(map[string]*measurement, entriesCount)
+	for i := range entries {
+		entry := &entries[i]
+		if entry.m.count > 0 {
+			result[string(entry.value[:entry.vlen])] = &entry.m
+		}
+	}
+	return result
+}
+
+func round(x float64) float64 {
+	return roundJava(x*10.0) / 10.0
+}
+
+// roundJava returns the closest integer to the argument, with ties
+// rounding to positive infinity, see java's Math.round
+func roundJava(x float64) float64 {
+	t := math.Trunc(x)
+	if x < 0.0 && t-x == 0.5 {
+		//return t
+	} else if math.Abs(x-t) >= 0.5 {
+		t += math.Copysign(1, x)
+	}
+
+	if t == 0 { // check -0
+		return 0.0
+	}
+	return t
+}
+
+// parseNumber reads decimal number that matches "^-?[0-9]{1,2}[.][0-9]" pattern,
+// e.g.: -12.3, -3.4, 5.6, 78.9 and return the value*10, i.e. -123, -34, 56, 789.
+func parseNumber(data []byte) int64 {
+	negative := data[0] == '-'
+	if negative {
+		data = data[1:]
+	}
+
+	var result int64
+	switch len(data) {
+	// 1.2
+	case 3:
+		result = int64(data[0])*10 + int64(data[2]) - '0'*(10+1)
+	// 12.3
+	case 4:
+		result = int64(data[0])*100 + int64(data[1])*10 + int64(data[3]) - '0'*(100+10+1)
+	}
+
+	if negative {
+		return -result
+	}
+	return result
+}
diff --git a/src/main/go/AlexanderYastrebov/calc_test.go b/src/main/go/AlexanderYastrebov/calc_test.go
new file mode 100644
index 0000000..db7e27a
--- /dev/null
+++ b/src/main/go/AlexanderYastrebov/calc_test.go
@@ -0,0 +1,86 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+func TestRoundJava(t *testing.T) {
+	for _, tc := range []struct {
+		value    float64
+		expected string
+	}{
+		{value: -1.5, expected: "-1.0"},
+		{value: -1.0, expected: "-1.0"},
+		{value: -0.7, expected: "-1.0"},
+		{value: -0.5, expected: "0.0"},
+		{value: -0.3, expected: "0.0"},
+		{value: 0.0, expected: "0.0"},
+		{value: 0.3, expected: "0.0"},
+		{value: 0.5, expected: "1.0"},
+		{value: 0.7, expected: "1.0"},
+		{value: 1.0, expected: "1.0"},
+		{value: 1.5, expected: "2.0"},
+	} {
+		if rounded := roundJava(tc.value); fmt.Sprintf("%.1f", rounded) != tc.expected {
+			t.Errorf("Wrong rounding of %v, expected: %s, got: %.1f", tc.value, tc.expected, rounded)
+		}
+	}
+}
+
+func TestParseNumber(t *testing.T) {
+	for _, tc := range []struct {
+		value    string
+		expected string
+	}{
+		{value: "-99.9", expected: "-999"},
+		{value: "-12.3", expected: "-123"},
+		{value: "-1.5", expected: "-15"},
+		{value: "-1.0", expected: "-10"},
+		{value: "0.0", expected: "0"},
+		{value: "0.3", expected: "3"},
+		{value: "12.3", expected: "123"},
+		{value: "99.9", expected: "999"},
+	} {
+		if number := parseNumber([]byte(tc.value)); fmt.Sprintf("%d", number) != tc.expected {
+			t.Errorf("Wrong parsing of %v, expected: %s, got: %d", tc.value, tc.expected, number)
+		}
+	}
+}
+
+var parseNumberSink int64
+
+func BenchmarkParseNumber(b *testing.B) {
+	data1 := []byte("1.2")
+	data2 := []byte("-12.3")
+
+	for i := 0; i < b.N; i++ {
+		parseNumberSink = parseNumber(data1) + parseNumber(data2)
+	}
+}
+
+func BenchmarkProcess(b *testing.B) {
+	// $ ./create_measurements.sh 1000000 && mv measurements.txt measurements-1e6.txt
+	// Created file with 1,000,000 measurements in 514 ms
+	const filename = "../../../../measurements-1e6.txt"
+
+	data, err := os.ReadFile(filename)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	measurements := process(data)
+	rows := int64(0)
+	for _, m := range measurements {
+		rows += m.count
+	}
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	b.ReportMetric(float64(rows), "rows/op")
+
+	for i := 0; i < b.N; i++ {
+		process(data)
+	}
+}
diff --git a/src/main/go/AlexanderYastrebov/go.mod b/src/main/go/AlexanderYastrebov/go.mod
new file mode 100644
index 0000000..08f5bd1
--- /dev/null
+++ b/src/main/go/AlexanderYastrebov/go.mod
@@ -0,0 +1,3 @@
+module github.com/AlexanderYastrebov/1brc
+
+go 1.21.5