I am trying to understand the inner workings of XCode's Instruments. On MacOS, it can rely on DTrace to gather all kinds of profiling data. On iOS, it is also capable of lots of things, but I have read repeatedly that DTrace has not been ported to iOS.
So how does that work?
The Apple documentation on DTrace isn't telling me much about the inner workings here. I have noticed, however, that when profiling my own App from XCode using Instruments, XCode seems to build it differently. Could that mean it links some standalone DTrace providers with my code?
Thanks in advance!
/e: I would bounty this question with my ENTIRE 6 REPUTATION POINTS if only i could...
For iOS apps running inside the Simulator, obviously the Simulator is a Mac OS X program, so it can use DTrace to monitor everything the Simulator does.
For iOS apps running on an iPhone, I agree the documentation provides little insight into what's happening. It's probably either loading monitoring code into the target process on iOS (either by adding the code at compile time or by linking it in at runtime) or there is an "traditional debugger" running on iOS against the target process to implement the tracing. Those are pretty much the only options if there is no kernel-level support for using DTrace.
I've never used Instruments, but the main thing that jumps out at me is that they're able to collect seemingly-OS-level statistics about I/O, which would not normally be measurable without DTrace. I'm not sure because I haven't used it, but it's possible these statistics are only tracking I/O from easy-to-detect entrypoints (ie I/O-related syscalls from the specific target process), or that there are other iOS-specific statistic sources which are published by the OS. For instance, many system statistics can be gotten from Mac OS X by calling sysctl. Depending on what statistics are actually being collected, Instruments could just be using simple counters like these to do most of the work.
If you're really determined to find the answer, it would be a fun DTrace challenge to figure this problem out by DTracing Instruments itself. Good luck :-)
Related
With the push towards multimedia enabled mobile devices this seems like a logical way to boost performance on these platforms, while keeping general purpose software power efficient. I've been interested in the IPad hardware as a developement platform for UI and data display / entry usage. But am curious of how much processing capability the device itself is capable of. OpenCL would make it a JUICY hardware platform to develop on, even though the licensing seems like it kinda stinks.
OpenCL is not yet part of iOS.
However, the newer iPhones, iPod touches, and the iPad all have GPUs that support OpenGL ES 2.0. 2.0 lets you create your own programmable shaders to run on the GPU, which would let you do high-performance parallel calculations. While not as elegant as OpenCL, you might be able to solve many of the same problems.
Additionally, iOS 4.0 brought with it the Accelerate framework which gives you access to many common vector-based operations for high-performance computing on the CPU. See Session 202 - The Accelerate framework for iPhone OS in the WWDC 2010 videos for more on this.
Caution! This question is ranked as 2nd result by google. However most answers here (including mine) are out-of-date. People interested in OpenCL on iOS should visit more update-to-date entries like this -- https://stackoverflow.com/a/18847804/443016.
http://www.macrumors.com/2011/01/14/ios-4-3-beta-hints-at-opencl-capable-sgx543-gpu-in-future-devices/
iPad2's GPU, PowerVR SGX543 is capable of OpenCL.
Let's wait and see which iOS release will bring OpenCL APIs to us.:)
Following from nacho4d:
There is indeed an OpenCL.framework in iOS5s private frameworks directory, so I would suppose iOS6 is the one to watch for OpenCL.
Actually, I've seen it in OpenGL-related crash logs for my iPad 1, although that could just be CPU (implementing parts of the graphics stack perhaps, like on OSX).
You can compile and run OpenCL code on iOS using the private OpenCL framework, but you probably don't get a project into the App Store (Apple doesn't want you to use private frameworks).
Here is how to do it:
https://github.com/linusyang/opencl-test-ios
OpenCL ? No yet.
A good way of guessing next Public Frameworks in iOSs is by looking at Private Frameworks Directory.
If you see there what you are looking for, then there are chances.
If not, then wait for the next release and look again in the Private stuff.
I guess CoreImage is coming first because OpenCL is too low level ;)
Anyway, this is just a guess
It's a great thing that it's possible to compile an SWF into iOS native app. I think AIR is now the best option to write e.g. small games or interactive books. Of cause AIR app will be slowler than the same app written on e.g. objective C. The question is how slower AIR app will be. Can simple AIR apps be launched e.g. on iPhone 3G or iPAd 1?
And another question is, can arbitrary flash app be compiled into iOS native app?
Will be grateful for any thoughts!!!!!
Performance of AIR vs. Objective C:
For pure script execution, AIR apps perform rather slower than native, including on iOS. However, in virtually all cases the limiting factor of your app's performance will be rendering, not script, so it depends entirely on what you do visually in your content. This is why Crooksy suggested you look at Starling. Without Starling (or similar libraries that make use of the GPU), it's pretty challenging to get decent performance out of an iPad1. It can be done, but it takes expertise and incurs extra work. It will be much better to start with the huge performance boost of using Starling or similar.
Can arbitrary flash app be compiled into iOS native app?
As long as it's made with AS3, then it should compile. For whether it works, two main caveats come to mind: First, a handful of APIs don't work on mobile devices. (I think printing is one example.) Second, if you read in any SWFs at runtime, all actionscript inside them will be ignored. (Not for technical reasons, it's an Apple requirement.) So if your content is split into a bunch of SWFs you'll need to bundle them together at packaging time, and if you absolutely depend on reading in SWFs with script from the network at runtime, you're going to hit a wall.
Hope that helps!
Check out the new Starling frame work.
http://gamua.com/
Here's the start of a nice tutorial series (episodes 1 and 2)
http://www.hsharma.com/tutorials/
Lee Brimelow also has a few tutorials
http://www.gotoandlearn.com/
Regarding converting Flash apps into iOS compatible apps, yes that is possible but it depends on what the app actually does as to whether any modifications will be needed before it will perform correctly on a device.
I want to port a good OpenCV code on an embedded platform. Earlier such stuffs were very difficult to perform but now TI has come up with nice embedded platforms which are comparatively hassle free as they say.
I want to know following things:
Given that :
The OpenCV code is already running on PC smoothly. (obviously)
Need to determine these before purchasing the device.
Can't put the code here in stackoverflow. :P
To chose from Texas Instruments: C6000.
Questions:
How to make it sure that the porting will be done?
What steps to be taken to make it sure that after porting the code, will run (at least).
to determine whether the code might require some changes to make its run smooth.
The point 3 above is optional.
I need info which will at least give me some start up in this regard.
What I thought I should do?
I am to list the inbuilt functions down.
Then to find available online bench marking for those functions for the particular device like as shown towards the end of this doc.
...
Need to know how to proceed further?
However C6-Integra™ DSP+ARM Processor seems the best.
The best you can do is to try a device simulator (if it is available), but what you'll see there is far from perfect.
Actually, nothing can tell you how fast and how well the app will run on the embedded device before running you specific app on that specific device.
So:
Step 1 Buy it
Step 2 Try it
Things to consider:
embedded CPU architecture: Your app needs a big cache? how big is the embedded cache?
algorithm: do you use a lot of floating point operations? how good is the device at floating point ops?
do you have memory transfers? data bus on a PC is waaay faster than on embedded
hardware support: do you use a lot of double-precision calculations? they are emulated on ARMs. They are gonna kill your app (from millisecons on a PC it can go to seconds on a ARM)
Acceleration. Do your functions use SSE? (many OpenCV funcs are SSEd, even if you don't know). Do you have the NEON counterpart? (OpenCV does not have much support for that). The difference can be orders of magnitude from x86 SSE to embedded without NEON.
and many, many others.
So, again: no one can tell you how it will work. Just the combination between the specific app and the real device tells the truth.
even a run on a similar device is not relevant. It can run smoothly on a given processor, and with another, with similar freq or listed memory, it will slow down too much
This is an interesting question but run is a very generic word in this context, therefore I feel the need to break it down to other 2 questions:
Will it compile in an embedded device?
Will it run as fast/smooth as in a PC?
I've used OpenCV in a lot of different devices, including ARM, SH4, MIPS and I found out that sometimes the manufacturer of the device itself provides a compiled version of OpenCV (for my surprise), which is great. That's something you can look into, maybe the manufacturer of your device provide OpenCV binaries.
There's no way to know for sure how smooth your OpenCV application will be on the target device unless you are able to find some benchmark of OpenCV running in there. PCs have far better processing power than embedded devices, so you can expect less performance from the target device.
There are 3rd party applications like opencv-performance, that you can use to test/benchmark the environment once you get your hands on it. And if performance is such a big deal in this project, you might also be interested in this nice article which explain some timing tests done on couple of OpenCV features comparing implementations using the C and C++ interfaces of OpenCV.
I recently started to learn how to use openCL to speed up some part of my code. So far the speed gain is impressive. In one case the code ran up to 50X faster than on the CPU. However I wonder if can start using this code in a production environnement. The reason is that the first time that I tried to run the example code, nothing worked. I was able to make it run by downloading the driver on the Nvidia openCL SDK download page (I have a Geforce GTX260). It gave me a blue during installation but after that I was able to run the example program and create my own code.
Does the fact that it didn't work "out of the box" for me mean that the mainstream drivers does not yet support it, despite the fact that it is specifically written that it does on the driver download page? What about ATI support? Will everyone have to download the special driver that gave me a blue screen on install?
In short, is openCL ready for production code?
If someone can give me some details, I'd like to know. Does anyone has been able to run a simple program on a number of different device without installing anything SDK related?
You may find an accurate answer on the OpenCL forums on the Khronos Group message boards. The OpenCL work group hangs out there regularly.
Does anyone has been able to run a
simple program on a number of
different device without installing
anything SDK related?
Nop. For instance, on ATI's GPUs end-users need to install ATI Stream SDK in order to run OpenCL code (just having an up-to-date graphics driver is not sufficient).
You may want to consider trying DirectCompute (Microsoft's version of GPU programming) or doing your OpenCL work on a Snow Leopard Mac. Those are the two ways (that I know of) that you can deliver a GPU programming solution to another user without any driver or other installation hassle.
Every indication I have, based on my experience in embedded computing is that doing something like this would require expensive equipment to get access to the platform (ICE debuggers, JTAG probes, I2C programmers, etc, etc), but I've always wondered if some ambitious hacker out there has found a way to load native code on a Blackberry device. Anyone?
Edit: I'm aware of the published SDK and it's attendant restrictions. I'm curious if anyone has attempted to get around them, and if so, how far they got.
I've seen this question pop up in a number of different forums over time. The original Blackberries were programmable in C++ but I think that RIM ran up against the problems of trying to implement a secure platform in the C/C++ compile to native paradigm.
The devices do have JTAG ports, but unless one could get hands on the RIM code as a place to start the problem is enormous.
I also have to wonder how useful a Blackberry with a replacement FOSS operating system would be, since it would not likely have the protocols to connect to BES or BIS, send PIN's etc. If one was simply looking for a the power of the hand held computing platform I suspect there are many more likely candidates available.
No, C++ is no longer a supported RIM development tool, as they phased it out a number of years ago. Client applications can be developed in Java (or one of a few 5GL frameworks), and web + sever-side apps can be developed using standard tools.
For those looking for updated information, the new Playbook os, also known as QNX, also known as Blackberry 10 (or it will be when the phones running it come out) is in fact c/c++ based, also using QML and a C++ add on called Cascades.
Unfortunately the official SDK website only seems to mention Java. According to wikipedia, different versions of the BlackBerry use different processors. Combined with the fact that RIM uses a proprietary operating system for the devices, it becomes pretty difficult to develop native code without official tools. There is also a partial API-level security restriction which would further prohibit advanced tinkering.
Just randomly searching for an answer to this and came across http://supportforums.blackberry.com/t5/Tablet-OS-SDK-for-Adobe-AIR/Native-C-C-SDK/td-p/778009 which mentions that BB intend to release a C/C++ SDK soon, more details will be provided at the 2011 Game Developer Conference.