attempt 10: ignore reading the decimal point when processing city temp

README.md

@@ -11,4 +11,5 @@
 |6|Convert temperature from `string` to `int64`, process in `int64` and convert to `float64` at the end. |2:51.50|-41.14|[7812da4](https://github.com/shraddhaag/1brc/commit/7812da4d0be07dd4686d5f9b9df1e93b08cd0dd1)|
 |7|In the city <> temperatures map, replaced the value for each key (city) to preprocessed min, max, count and sum of all temperatures instead of storing all recorded temperatures for the city.|1:39.81|-71.79|[e5213a8](https://github.com/shraddhaag/1brc/commit/e5213a836b17bec0a858474a11f07c902e724bba)|
 |8|Use producer consumer pattern to read file in chunks and process the chunks in parallel.|1:43.82|+14.01|[067f2a4](https://github.com/shraddhaag/1brc/commit/067f2a44c0d6b3bb7cc073639364f733bce09e3e)|
-|9|Reduce memory allocation by processing each read chunk into a map. Result channel now can collate the smaller processed chunk maps.|0:28.544|-75.286||
+|9|Reduce memory allocation by processing each read chunk into a map. Result channel now can collate the smaller processed chunk maps.|0:28.544|-75.286|[d4153ac](https://github.com/shraddhaag/1brc/commit/d4153ac7a841170a5ceee47d930e97738b5a19f6)|
+|10|Avoid string concatenation overhead by not reading the decimal point when processing city temperature.|0:24.571|-3.973||

main.go

@@ -176,24 +176,19 @@ func readFileLineByLineIntoAMap(filepath string) (map[string]cityTemperatureInfo
 	return mapOfTemp, nil
 }
 
-func convertStringToInt64(input string) int64 {
-	input = input[:len(input)-2] + input[len(input)-1:]
-	output, _ := strconv.ParseInt(input, 10, 64)
-	return output
-}
-
 func processReadChunk(buf []byte, resultStream chan<- map[string]cityTemperatureInfo) {
 	var stringsBuilder strings.Builder
 	toSend := make(map[string]cityTemperatureInfo)
 	var city string
 
 	for _, char := range buf {
-		if char == ';' {
+		switch char {
+		case ';':
 			city = stringsBuilder.String()
 			stringsBuilder.Reset()
-		} else if char == '\n' {
+		case '\n':
 			if stringsBuilder.Len() != 0 && len(city) != 0 {
-				temp := convertStringToInt64(stringsBuilder.String())
+				temp, _ := strconv.ParseInt(stringsBuilder.String(), 10, 64)
 				stringsBuilder.Reset()
 
 				if val, ok := toSend[city]; ok {
@@ -215,8 +210,14 @@ func processReadChunk(buf []byte, resultStream chan<- map[string]cityTemperature
 						sum:   temp,
 					}
 				}
+
+				city = ""
+			}
+		case '.':
+			if len(city) == 0 {
+				stringsBuilder.WriteByte(char)
 			}
-		} else {
+		default:
 			stringsBuilder.WriteByte(char)
 		}
 	}