Fergus Mac Roich posted:

I happen to have a brand new OnePlus 3. I just plugged it in with "USB Debugging" enabled and it seemed to install the drivers just fine. I happen to be doing a fresh install of Android Studio as we speak so I'll update on what happens there with a default application.

fake-edit: This is connected to a Windows 10 PC with the latest large update that came out recently.

FWIW, I have an i5-3570 and the emulator hasn't ever been unusably slow in the past, though it is slow.

Real-edit: Okay, I got Android Studio up and running. It prompts you on the OnePlus 3 itself before you're able to run the app on your device; is your device unlocked while you're doing all this? My best guess other than that would be some kind of old driver version conflict, something like that.

Jo posted:

I have an OpenCL application I'm making with JoCL and I'm having a hard time figuring out why the hotspots are what they are. The Java Mission Control application says that my program is spending most of its time in java.lang.integer.equals. That seems completely wrong.

Jabor posted:

The screenshot says that almost all of that time being spent in equals because ArrayList.indexOf is calling equals a lot. That seems completely plausible if indexOf is being called a lot on big lists - every call to indexOf effectively iterates over the entire list to try and find the right element.

If you expand the list of things that call indexOf (and keep expanding until you see something you recognize), does that clarify what's being slow?

Zaphod42 posted:

Try changing shapes from List to HashMap and see how that effects the performance. You call getShape() a lot in GPUGraph.java and that's O(N) each time.

Sorry, I can't answer your real question, haven't had to debug C++ calls from Java and I'm not sure how to go about that either.

You won't be able to attach to the java program, so you'll probably have to attach to the shared library. You may even have to get a debug build of the library and compile your java program against the debug library before it'll work.

Jo posted:

Isn't ArrayList O(1)? I get that a Linked List would be O(n), but an array list should be as fast as a direct memory seek.

In either case, it's still hard for me to believe that the program is spending 50% of its time doing isEqual when the graph has only twelve nodes. Even with a non-memoized implementation that shouldn't be more than 144 calls to the method compared to 1000*1000 multiplications PER LOOP.

Fake Edit: The doc says an array list access should be O(1). It's just doing an array lookup.

Zorro KingOfEngland posted:

ArrayList's .get() is O(1), but .indexOf() is O(n) because you have to get each object and test its equality until you find the one you're looking for.

If you look at the source code for ArrayList's indexOf you'll see that it just loops through elements until it finds one that equals: Here

A HashMap like Zaphod42 was suggesting would probably be a better fit for your problem.

efb.

Jo posted:

Aha! Well I'll have to trace down where index of is being called. If get() is actually calling it, I'd call that a bug in the docs because it means the runtime isn't as advertised. I'll just switch to a standard array and resize it as I add elements to the graph. No need to use a hashmap.

Edit: OpenJDK's source indicates it's constant time. I wonder where that indexOf is getting called. Maybe I'm going down the rabbit hole with this one. Even with a fuckload of linear seeks, there's no way that finding an item in a list of length 12 takes 50% of a five-minute run. I think it's just the case that Java mission control can't effectively profile stuff that's native. It's probably not counting the two-minute matrix multiply or 30-second opencl compile. Treats it as blocked io?

Zaphod42 posted:

Try changing shapes from List to HashMap and see how that effects the performance. You call getShape() a lot in GPUGraph.java and that's O(N) each time.

Jo posted:

Aha! Well I'll have to trace down where index of is being called. If get() is actually calling it, I'd call that a bug in the docs because it means the runtime isn't as advertised. I'll just switch to a standard array and resize it as I add elements to the graph. No need to use a hashmap.

Edit: OpenJDK's source indicates it's constant time. I wonder where that indexOf is getting called.

Zaphod42 posted:

I already told you. IndexOf is called in getShape().

code:

if(shapes.contains(node)) {
	return shapes.get(node);
}

That's O(N) each time, and you call getShape() multiple times. How big is the shapes arraylist and how many times are you calling it? HashMap would make that O(1).

I guess that's not indexOf() in particular, although I wouldn't be surprised if contains() just returns indexof(o) == -1.

For that matter, looking at your code, is shapes.contains(node) even what you want there?

You put Dimension objects into the Shapes ArrayList. Contains(int) will always return null, wont it? Seems like you're trying to do contains(index) but that's not what the contains() method does. Contains is for passing an object that would be in the array, not an index.

code:

try{
  Shape s = shapes.get(node);
  if(s != null) {
	return s;
  }
}
catch(IndexOutOfBoundsException e)
{
//nothing found
}
//do other stuff

Squashy Nipples posted:

Hey guys, after 9 months off, I'm back to teaching myself Java (slowly).

Look what I just tried:

code:

int[i] ++;

It' doesn't work, and neither did this:

code:

int[i] = int[i] + 1;

I have a cup of dice, and I want to return a 6-member array of integers, each containing the number of occurrences of each side.
(6-member array because they are six-sided dice, and the cup can contain any number of dice)

code:

    public int[] resultCount(){
        
        int[] temp = new int[6];
        
        for ( int i = 0 ; i < 6 ; i ++){
            for (Die die : cup ){
                if (die.getSide() == i) {
                    int[i] = int[i] + 1;
                }
            }
        }
        return temp;
    }

Advice, please.

smackfu posted:

When do you change the value of temp?

And don't call variables "temp".

carry on then posted:

I'm curious what error you're getting from the compiler.

Squashy Nipples posted:

One last question: when you initialize an array like I did ( int[] results = new int[6]; ), do I get an array of zeros, or an array of NULLs?

Squashy Nipples posted:

Ornithology posted:

Can anyone recommend a guide for a beginner to learn the Spring framework?

My teacher has been showing us how to build very basic Java Web applications using NetBeans and now we have an assignment to make a Spring MVC application. I'm really getting overwhelmed. I tried using the NetBeans template for Spring MVC but it seems they use deprecated classes which their guide acknowledges but provides no recourse.

I tried looking at some examples from the book Spring in Action 4th edition but it seems like they use a completely different build structure which I can't even open in NetBeans, and starting a NetBeans Spring project and then following the textbook ends up with all kinds of import errors.

Overall I'm very confused as it seems to be totally different than the bare bones servlets we have made in class so far. I haven't even got a hello world example to run properly yet...

Paul MaudDib posted:

Also, IntelliJ is by far the best IDE in the Java world and you get a free copy as a student so you should do that too.

Trapick posted:

For beginners (but not student, so would cost dollars), is the Ultimate edition significantly better than the Community edition?

Trapick posted:

For beginners (but not student, so would cost dollars), is the Ultimate edition significantly better than the Community edition?

Ornithology posted:

Thanks for the suggestions regarding the Spring framework, guys. I've got Hello World working now at least but I've run into an issue with iterating over a collection in a jsp file. Any helps would be highly appreciated.. I'm sure it's a simple fix that I'm missing.

edit: Fixed - code removed, I was missing taglib reference on the jsp page

ToxicSlurpee posted:

Jsp files are...kind of poo poo. Look into thymeleaf for you templates.

ToxicSlurpee posted:

Jsp files are...kind of poo poo. Look into thymeleaf for you templates.

Ornithology posted:

Thanks for the suggestion. The curriculum in my school program seems pretty out of date so it's always good to know the better options that I should be learning!