I had:
    tb = SummaryWriter()
    args.tb = tb

but nothing appeared when I had
tb.add_scalar('loss', loss, i)

Why?
Do I have to have the folder defined before hand? Or does tensorboard create the folders by itself if they need to be created?

Follow up, where is the dir?
Ok the docs say:
log_dir (string) – Save directory location. Default is runs/CURRENT_DATETIME_HOSTNAME, which changes after each run. Use hierarchical folder structure to compare between runs easily. e.g. pass in ‘runs/exp1’, ‘runs/exp2’, etc. for each new experiment to compare across them

but its not here:
cd /runs
cd: no such file or directory: /runs