Custom atoi/atof parser logic, plus math changes.

This commit uses a custom atoi function that converts 12.4 to 124 so we
can do integer math instead of using doubles.

calculate_average_fragmede.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+#
+#  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.
+#
+
+
+JAVA_OPTS="-Xmx16g"
+time java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_fragmede measurements.txt
+

src/main/java/dev/morling/onebrc/CalculateAverage_fragmede.java

@@ -0,0 +1,109 @@
+/*
+ *  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.
+ */
+package dev.morling.onebrc;
+
+import static java.util.stream.Collectors.*;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.stream.Collector;
+
+public class CalculateAverage_fragmede {
+
+    private static final String FILE = "./measurements.txt";
+    // private static final String FILE = "./yaku.txt";// "./measurements.txt";
+
+    private static record Measurement(String station, int value) {
+		public static Measurement of(String[] parts) {
+			//System.out.printf("string: %s!\n", parts[1]);
+			boolean negative = false;
+			int idx = 0;
+			if (parts[1].charAt(0) == '-') {
+				negative = true;
+				idx = 1;
+			}
+			int digit = (parts[1].charAt(idx)-48) * 10;
+			int digit2 = 0;
+			if (parts[1].charAt(idx+1) != '.') {
+				// two digit temperature
+				digit = (digit) * 10;
+				//System.out.println(parts[1].charAt(idx+1));
+				digit2 = (parts[1].charAt(idx+1)-48)*10;
+				idx++;
+			}
+			// if (parts[1].charAt(idx+2) != ".") {
+			// 	abort();
+			// }
+			int frac = parts[1].charAt(idx+2)-48;
+			//System.out.printf("parts, %d:%d:%d\n", digit, digit2, frac);
+			int value = digit + digit2 + frac;
+			if (negative) {
+				value = -value;
+			}
+			//System.out.printf("end value: %d\n", value);
+			return new Measurement(parts[0], value);
+		}
+	}
+
+    private static record ResultRow(double min, double mean, double max) {
+        public String toString() {
+            return min + "/" + round(mean) + "/" + max;
+        }
+
+        private double round(double value) {
+            return Math.round(value * 10.0) / 10.0;
+        }
+    };
+
+    private static class MeasurementAggregator {
+        private double min = Double.POSITIVE_INFINITY;
+        private double max = Double.NEGATIVE_INFINITY;
+        private double sum;
+        private long count;
+    }
+
+    public static void main(String[] args) throws IOException {
+        Collector<Measurement, MeasurementAggregator, ResultRow> collector = Collector.of(
+                MeasurementAggregator::new,
+                (a, m) -> {
+                    a.min = Math.min(a.min, m.value);
+                    a.max = Math.max(a.max, m.value);
+                    a.sum += m.value;
+                    a.count++;
+                },
+                (agg1, agg2) -> {
+                    var res = new MeasurementAggregator();
+                    res.min = Math.min(agg1.min, agg2.min);
+                    res.max = Math.max(agg1.max, agg2.max);
+                    res.sum = agg1.sum + agg2.sum;
+                    res.count = agg1.count + agg2.count;
+
+                    return res;
+                },
+                agg -> {
+                    return new ResultRow(agg.min / 10.0, agg.sum / 10.0 / agg.count, agg.max / 10.0);
+                });
+
+        Map<String, ResultRow> measurements = new TreeMap<>(Files.lines(Paths.get(args[0]))
+                .map(l -> Measurement.of(l.split(";")))
+                .collect(groupingBy(Measurement::station, collector)));
+
+        System.out.println(measurements);
+    }
+}