How to re-enable the caps lock key?

Question

I have the following situation:

I create a boost::thread_group instance, then create threads for parallel-processing on some data, then join_all on the threads.

Initially I created the threads for every X elements of data, like so:

// begin = someVector.begin();
// end = someVector.end();
// batchDispatcher = boost::function<void(It, It)>(...);

boost::thread_group     processors;

// create dispatching thread every ASYNCH_PROCESSING_THRESHOLD notifications
while(end - begin > ASYNCH_PROCESSING_THRESHOLD)
{
    NotifItr split = begin + ASYNCH_PROCESSING_THRESHOLD;

    processors.create_thread(boost::bind(batchDispatcher, begin, split));
    begin = split;
}

// create dispatching thread for the remainder
if(begin < end)
{
    processors.create_thread(boost::bind(batchDispatcher, begin, end));
}

// wait for parallel processing to finish
processors.join_all();

but I have a problem with this: When I have lots of data, this code is generating lots of threads (> 40 threads) which keeps the processor busy with thread-switching contexts.

My question is this: Is it possible to call create_thread on the thread_group after the call to join_all.

That is, can I change my code to this?

boost::thread_group     processors;
size_t                  processorThreads = 0; // NEW CODE

// create dispatching thread every ASYNCH_PROCESSING_THRESHOLD notifications
while(end - begin > ASYNCH_PROCESSING_THRESHOLD)
{
    NotifItr split = begin + ASYNCH_PROCESSING_THRESHOLD;

    processors.create_thread(boost::bind(batchDispatcher, begin, split));
    begin = split;

    if(++processorThreads >= MAX_ASYNCH_PROCESSORS) // NEW CODE
    {                               // NEW CODE
        processors.join_all();      // NEW CODE
        processorThreads = 0;       // NEW CODE
    }                               // NEW CODE
}

// ... 

Whoever has experience with this, thanks for any insight.

Solution 1

The following commands should work:

xmodmap -e 'keycode 0x42 = Caps_Lock'

or

setxkbmap -option

The commands above work just fine to restore the default behaviour, which I hardly ever need, luckily.

I normally remap the capslock to Control (luckily VI/VIM supports CTRL-C instead of ESC) with the following command:

setxkbmap -option ctrl:nocaps -layout gb

Solution 2

Try setxkbmap -option -layout us -variant dvorak-l -option ctrl:swapcaps

From the manpage:

[...] If you want to
replace all previously specified options, use the -option  flag
with an empty argument first.

Irony is that here -option ctrl:swapcaps actually overrides -option ctrl:nocaps — I guess the behavior changed.

Edit: As the OP stated, he wants to avoid clearing the options (as done in the way above).

/usr/share/X11/xkb/rules/xorg.lst shows the option ctrl:aa_ctrl (control at bottom left), which seems to reset caps lock after nocaps here.

I guess it's worth a try, and you can also look at the list (grep ctrl\:) and see if there's something else which may work, in case this one doesn't.

If there's no option for this, I guess the solution is to hack the current keymap, by associating Caps Lock with the Caps Lock key again (but I don't have experience with that, other than believing there's a tool that allows you to do that with a one-liner).

Comments

[hhaamu]

I'm guessing everyone who tried to help me got their keyboards stuck to dvorak =(

[jw013]

X is so old and complex now that not many people really understand the various internal mechanisms. There's even sections in the man page that says (and I quote): "Nobody wants to say how this works. Maybe nobody knows ...". I am interested in seeing an answer to this question as well but it may be the case that nobody knows ...

[utnapistim]

The code was working as it was (as in my proposed solution) but I wasn't sure it was stable. I have implemented a version that explicitly removes dead threads after join_all. It is not the most efficient of implementations, but it'll do for now (as advised here: groups.google.com/group/boost-list/browse_thread/thread/…) I will also look into implementing a producer-consumer solution (thanks).

[hhaamu]

That indeed does clear the options list, but I wish to keep the non-caps-related options (as I stated in the question) such as compose keys.

[kmacdonald]

Oh, sorry, I misread the question. I can't be sure if this will work (as I stated, swapcaps actually re-enables caps lock here), but from /usr/share/X11/xkb/rules/xorg.lst, I see there is the option ctrl:aa_ctrl (control at bottom left), which seems to reset caps lock after nocaps here.

[hhaamu]

I think the magic program is xmodmap but I'm not quite sure how to use it