Waitgroups in VHDL

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity WaitGroups is
end WaitGroups;

architecture Behavioral of WaitGroups is
    -- Define a type for the worker process
    type worker_type is protected
        procedure start(id : in integer);
        procedure wait_for_completion;
    end protected;

    -- Implementation of the worker_type
    type worker_type is protected body
        variable count : integer := 0;
        
        procedure start(id : in integer) is
        begin
            count := count + 1;
            report "Worker " & integer'image(id) & " starting";
            -- Simulate an expensive task
            wait for 1 sec;
            report "Worker " & integer'image(id) & " done";
            count := count - 1;
        end procedure;
        
        procedure wait_for_completion is
        begin
            wait until count = 0;
        end procedure;
    end protected body;

    shared variable wg : worker_type;
begin
    -- Main process
    process
    begin
        -- Launch several worker processes
        for i in 1 to 5 loop
            wg.start(i);
        end loop;

        -- Wait for all workers to finish
        wg.wait_for_completion;
        
        wait;
    end process;
end Behavioral;

This VHDL code demonstrates a concept similar to WaitGroups in Go, adapted for the hardware description language context. Here’s an explanation of the code:

1. We define a protected type worker_type that encapsulates the functionality of starting workers and waiting for their completion. This is analogous to the sync.WaitGroup in the original Go code.

2. The worker_type has two procedures:

   • start: Increments a counter, simulates work by waiting for 1 second, and then decrements the counter.
   • wait_for_completion: Waits until the counter reaches zero, indicating all workers have finished.

3. In the main process, we launch 5 worker processes using a for loop. Each call to wg.start(i) is similar to spawning a goroutine in Go.

4. After launching all workers, we call wg.wait_for_completion() to wait for all workers to finish, similar to wg.Wait() in Go.

5. The report statements are used to print messages, simulating the fmt.Printf calls in the original Go code.

Note that VHDL is a hardware description language, so concepts like goroutines and wait groups don’t have direct equivalents. This example uses VHDL’s concurrent processes and a protected type to achieve similar functionality.

To simulate this design, you would need to use a VHDL simulator such as ModelSim or GHDL. The output would show the workers starting and finishing, potentially in a different order each time due to the concurrent nature of the processes.