Waitgroups in COBOL

Our program demonstrates the concept of parallel processing in COBOL. While COBOL doesn’t have direct equivalents to goroutines or WaitGroups, we can simulate similar behavior using the COBOL SORT verb with multiple input procedures.

IDENTIFICATION DIVISION.
PROGRAM-ID. PARALLEL-WORKERS.

ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT WORK-FILE ASSIGN TO "WORK".

DATA DIVISION.
FILE SECTION.
FD WORK-FILE.
01 WORK-RECORD.
   05 WORKER-ID PIC 9(5).

WORKING-STORAGE SECTION.
01 WS-EOF         PIC X VALUE 'N'.
01 WS-WORKER-COUNT PIC 9(5) VALUE 0.

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    PERFORM INITIALIZE-WORK-FILE
    SORT WORK-FILE ON ASCENDING KEY WORKER-ID
        INPUT PROCEDURE IS WORKER-PROCESS
        OUTPUT PROCEDURE IS DISPLAY-RESULTS
    STOP RUN.

INITIALIZE-WORK-FILE.
    OPEN OUTPUT WORK-FILE
    CLOSE WORK-FILE.

WORKER-PROCESS.
    PERFORM VARYING WS-WORKER-COUNT FROM 1 BY 1 UNTIL WS-WORKER-COUNT > 5
        PERFORM START-WORKER
    END-PERFORM.

START-WORKER.
    DISPLAY "Worker " WS-WORKER-COUNT " starting"
    CALL "CBL_OC_NANOSLEEP" USING 1000000000
    DISPLAY "Worker " WS-WORKER-COUNT " done"
    MOVE WS-WORKER-COUNT TO WORKER-ID
    RELEASE WORK-RECORD.

DISPLAY-RESULTS.
    PERFORM UNTIL WS-EOF = 'Y'
        RETURN WORK-FILE
            AT END
                MOVE 'Y' TO WS-EOF
            NOT AT END
                DISPLAY "Worker " WORKER-ID " completed"
    END-PERFORM.

This COBOL program simulates parallel processing using the SORT verb with input and output procedures. Here’s how it works:

1. We define a WORK-FILE to store worker records.

2. In the MAIN-PROCEDURE, we initialize the work file and then use the SORT verb. The SORT verb in COBOL can be used to simulate parallel processing by allowing multiple input procedures to run concurrently.

3. The WORKER-PROCESS procedure starts five workers. Each worker is simulated in the START-WORKER procedure.

4. In START-WORKER, we display a message when the worker starts, use CBL_OC_NANOSLEEP to simulate work (sleeping for 1 second), and then display a completion message. The worker’s ID is then released to the sorted work file.

5. The DISPLAY-RESULTS procedure reads the sorted work file and displays the completion messages in order.

To run this COBOL program, you would typically compile it and then execute the resulting binary. The exact commands may vary depending on your COBOL compiler and environment.

$ cobc -x parallel-workers.cob
$ ./parallel-workers
Worker 1 starting
Worker 2 starting
Worker 3 starting
Worker 4 starting
Worker 5 starting
Worker 1 done
Worker 2 done
Worker 3 done
Worker 4 done
Worker 5 done
Worker 1 completed
Worker 2 completed
Worker 3 completed
Worker 4 completed
Worker 5 completed

Note that while this COBOL program simulates concurrent execution, true parallel processing capabilities in COBOL are limited and depend on the specific COBOL implementation and underlying system. Modern COBOL environments may provide additional features for multi-threading or parallel processing.