bytes.Count()-based Go implementation

Makefile

@@ -76,6 +76,7 @@ report.md: ada.time ada.version \
 	fpc.time fpc.version \
 	go.time go.version \
 	go.001.unroll.time go.version \
+	go.002.time go.version \
 	java.time java.version \
 	graalvm.time graalvm.version \
 	nim.time nim.version \

go.002/gc.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"bufio"
+        "bytes"
+	"fmt"
+	"log"
+	"os"
+)
+
+func main() {
+	// Open file
+	file, err := os.Open("chry_multiplied.fa")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	scan := bufio.NewScanner(file)
+
+        cgCount := 0
+        acgtCount := 0
+	cSlice := []byte{'C'}
+	gSlice := []byte{'G'}
+	nSlice := []byte{'N'}
+	for scan.Scan() {
+		line := scan.Bytes()
+		if line[0] == '>' {
+			continue
+		}
+		// The Count2Bytes() function in
+		//   github.com/grailbio/base/simd/count_amd64.{go,s}
+		// illustrates a further Go-accessible SIMD speedup of this
+		// part.  (Yes, I prefer C/C++/Rust intrinsics for SIMD, but Go
+		// doesn't completely lock you out.)
+		cgCount += bytes.Count(line, cSlice)
+		cgCount += bytes.Count(line, gSlice)
+
+		// Minor exploit of problem statement: instead of counting As
+		// and Ts, we can just count Ns and subtract from length, since
+		// we are guaranteed that the line contains only {A,C,G,T,N}.
+		acgtCount += len(line) - bytes.Count(line, nSlice)
+	}
+
+	gcFraction := float64(cgCount) / float64(acgtCount)
+	fmt.Println(gcFraction * 100)
+}