Atomic Counters in COBOL

Here’s the translation of the atomic counters example from Go to COBOL, with explanations in Markdown format suitable for Hugo:

In COBOL, we don’t have direct equivalents for goroutines or atomic operations. However, we can demonstrate a similar concept using separate programs and shared memory. Here’s an example that simulates the atomic counter using COBOL:

IDENTIFICATION DIVISION.
PROGRAM-ID. ATOMIC-COUNTER.

ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT COUNTER-FILE ASSIGN TO "counter.dat"
        ORGANIZATION IS LINE SEQUENTIAL.

DATA DIVISION.
FILE SECTION.
FD COUNTER-FILE.
01 COUNTER-RECORD.
    05 COUNTER-VALUE PIC 9(10).

WORKING-STORAGE SECTION.
01 WS-COUNTER PIC 9(10) VALUE 0.
01 WS-EOF PIC X VALUE 'N'.

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    PERFORM INITIALIZE-COUNTER
    PERFORM INCREMENT-COUNTER 50000 TIMES
    PERFORM DISPLAY-RESULT
    STOP RUN.

INITIALIZE-COUNTER.
    OPEN I-O COUNTER-FILE
    READ COUNTER-FILE
        AT END
            MOVE 0 TO COUNTER-VALUE
            WRITE COUNTER-RECORD
        NOT AT END
            MOVE COUNTER-VALUE TO WS-COUNTER
    END-READ
    CLOSE COUNTER-FILE.

INCREMENT-COUNTER.
    OPEN I-O COUNTER-FILE
    READ COUNTER-FILE
    ADD 1 TO COUNTER-VALUE
    REWRITE COUNTER-RECORD
    CLOSE COUNTER-FILE.

DISPLAY-RESULT.
    OPEN INPUT COUNTER-FILE
    READ COUNTER-FILE
        AT END
            MOVE 'Y' TO WS-EOF
        NOT AT END
            MOVE COUNTER-VALUE TO WS-COUNTER
    END-READ
    CLOSE COUNTER-FILE
    DISPLAY "ops: " WS-COUNTER.

This COBOL program simulates an atomic counter using a file-based approach. Here’s how it works:

1. We use a file counter.dat to store the counter value, which acts as our shared memory.

2. The INITIALIZE-COUNTER paragraph sets up the initial counter value, creating the file if it doesn’t exist.

3. The INCREMENT-COUNTER paragraph simulates the atomic increment operation. It opens the file, reads the current value, increments it, and writes it back.

4. We perform the increment operation 50,000 times, similar to the original example with 50 goroutines each incrementing 1,000 times.

5. Finally, the DISPLAY-RESULT paragraph reads the final counter value and displays it.

To run this program, you would compile it and then execute it:

$ cobc -x atomic-counter.cob
$ ./atomic-counter
ops: 50000

This approach doesn’t provide true atomicity or concurrency like the Go example, but it demonstrates a way to manage a shared counter in COBOL. In a real-world scenario, you might use COBOL’s built-in features for multi-threading or interface with system-level locking mechanisms for true atomic operations.

Next, we could explore COBOL’s file handling and record locking features for more advanced concurrent operations.