Concurrency Coordination Reports

Atomic Counter Coordination Report

Accumulate a shared count with an atomic integer and classify the result.

atomic counter An `AtomicInteger` keeps a running total consistent even when several workers update it, so a coordination report can read one final value.

Atomic Counter Coordination Report

step
AtomicCounterCoordinationReport.java
Replay: real traced execution (multi-file project)
import java.util.concurrent.atomic.AtomicInteger;

public class AtomicCounterCoordinationReport {
    public static void main(String[] args) {
        int step = 2;
        AtomicInteger counter = new AtomicInteger(0);

        for (int i = 0; i < 4; i++) {
            counter.addAndGet(step);
        }

        int total = counter.get();
        String status = total <= 4 ? "low" : total <= 8 ? "ok" : "high";

        System.out.println("step=" + step + " total=" + total + " status=" + status);
    }
}

import java.util.concurrent.atomic.AtomicInteger;

public class AtomicCounterCoordinationReport {
    public static void main(String[] args) {
        int step = 1;
        AtomicInteger counter = new AtomicInteger(0);

        for (int i = 0; i < 4; i++) {
            counter.addAndGet(step);
        }

        int total = counter.get();
        String status = total <= 4 ? "low" : total <= 8 ? "ok" : "high";

        System.out.println("step=" + step + " total=" + total + " status=" + status);
    }
}

import java.util.concurrent.atomic.AtomicInteger;

public class AtomicCounterCoordinationReport {
    public static void main(String[] args) {
        int step = 3;
        AtomicInteger counter = new AtomicInteger(0);

        for (int i = 0; i < 4; i++) {
            counter.addAndGet(step);
        }

        int total = counter.get();
        String status = total <= 4 ? "low" : total <= 8 ? "ok" : "high";

        System.out.println("step=" + step + " total=" + total + " status=" + status);
    }
}

  1. step ← 2, counter ← 0

    3public class AtomicCounterCoordinationReport {4    public static void main(String[] args) {5        int step→ 2 = 2;  //@step=1, 36        AtomicInteger counter→ 0 = new AtomicInteger(0);

  2. for (int i = 0; i < 4; i++)

    pass 1 of 4
    8for (int i0 = 0; i < 4; i++) {9    counter.addAndGet(step2);10}
    All 4 passes — pass 1 is the card above
    passi
    10
    21
    32
    43

  3. total ← 8, status ← ok

    12    int total→ 8 = counter.get();13    String status→ ok = total8 <= 4 ? "low" : total <= 8 ? "ok" : "high";1415    System.out.println("step=" + step2 + " total=" + total8 + " status=" + statusok);16}
    outputstep=2 total=8 status=ok

  1. step ← 1, counter ← 0

    3public class AtomicCounterCoordinationReport {4    public static void main(String[] args) {5        int step→ 1 = 1;6        AtomicInteger counter→ 0 = new AtomicInteger(0);

  2. for (int i = 0; i < 4; i++)

    pass 1 of 4
    8for (int i0 = 0; i < 4; i++) {9    counter.addAndGet(step1);10}
    All 4 passes — pass 1 is the card above
    passi
    10
    21
    32
    43

  3. total ← 4, status ← low

    12    int total→ 4 = counter.get();13    String status→ low = total4 <= 4 ? "low" : total <= 8 ? "ok" : "high";1415    System.out.println("step=" + step1 + " total=" + total4 + " status=" + statuslow);16}
    outputstep=1 total=4 status=low

  1. step ← 3, counter ← 0

    3public class AtomicCounterCoordinationReport {4    public static void main(String[] args) {5        int step→ 3 = 3;6        AtomicInteger counter→ 0 = new AtomicInteger(0);

  2. for (int i = 0; i < 4; i++)

    pass 1 of 4
    8for (int i0 = 0; i < 4; i++) {9    counter.addAndGet(step3);10}
    All 4 passes — pass 1 is the card above
    passi
    10
    21
    32
    43

  3. total ← 12, status ← high

    12    int total→ 12 = counter.get();13    String status→ high = total12 <= 4 ? "low" : total <= 8 ? "ok" : "high";1415    System.out.println("step=" + step3 + " total=" + total12 + " status=" + statushigh);16}
    outputstep=3 total=12 status=high