Restarting from Checkpoint, multiple runs, always reverts back to first checkpoint.

[corsair20141]

Hello, I am trying to create multiple checkpoints, esentially in a loop to ask the user if they would like to iterate 2 more generations or be done with the initial optimization run. However, if I try and continue the loop twice, the second time (and subsequent times) just restarts from the original checkpoint n_gen rather than the latest checkpoint n_gen.

How can I fix this? Is it a bug in Pymoo or an error on my part?

 res = minimize(problem,
             algorithm,
             termination,
             #seed=1,
             copy_algorithm=False,
             save_history=True,
             verbose=True) 

if os.path.exists("checkpoint"): # remove "checkpoint" file if already exists, before creating new one
    os.remove("checkpoint")
with open("checkpoint", "wb") as f: # create checkpoint file
    dill.dump(algorithm, f)
    
elapsed_time = time.time() - start_time
print(f"Optimization runtime: {elapsed_time/60:.2f} min")

# Offer to run n_gen_continue more generations
while True:
    n_gen_continue = 2
    
    selec1 = input(f"\n\n>>> Continue for another {n_gen_continue} generations? (y/n): ")
    if selec1 == "Y" or selec1 == "y": # then continue optimizaiton for another "n_gen_continue" generations
        print("\nContinuing...")
        with open("checkpoint", 'rb') as f:
            checkpoint = dill.load(f)
            print("> Loaded Checkpoint:", checkpoint)
            print("\n\n")
        start_time = time.time()
     
        checkpoint.termination = MaximumGenerationTermination(checkpoint.n_gen + n_gen_continue)
        res = minimize(problem,
                    checkpoint,
                    #seed=1,
                    copy_algorithm=True,
                    save_history=True,
                    verbose=True) 
        # if os.path.exists("checkpoint"): # remove "checkpoint" file if already exists, before creating new one
        #     os.remove("checkpoint")
        with open("checkpoint", "wb") as f: # create checkpoint
            dill.dump(algorithm, f)
                
        elapsed_time = time.time() - start_time
        print(f"Optimization runtime: {elapsed_time/60:.2f} min")
        
    elif selec1 == "N" or selec1 == "n": # then don't continue optimization
        break
    
    else:
        print("***Invalid selection ***")