I need to declare an array passed to a function as volatile, does Cudafy.NET support this?
For example (in C#):
[Cudafy]
private static void doStuffOnGPU(GThread thread, volatile int[] output)
{
//do a whole bunch of stuff
}
The answer is no, as of November 26, 2016, Cudafy.NET does not support the volatile keyword. However, you can tricksify Cudafy.NET into allowing it in certain circumstances.
Ex:
//declare a dummy in global scope
public static int[] volatileArray = new int[256];
[Cudafy]
private static void doStuffOnGPU(GThread thread, int[] output)
{
//use the GThread.InsertCode() function to declare in CUDA
GThread.InsertCode("__shared__ volatile int volatileArray[256];");
//do a whole bunch of stuff
}
This code will use the global declaration when run serially for testing and will use the volatile declaration on the GPU.
Related
This post is a duplicate of the Github Issue here.
dart --version
Dart SDK version: 2.15.0-116.0.dev (dev) (Thu Sep 16 09:47:01 2021 -0700) on "linux_x64"
I've been looking up examples for callbacks and I have tried to get callbacks working for me in FFI.
My current situation
I have a function in my library which expects a pointer to a function. The bindings for the same generated by ffigen seem correct to me.
int SetCallback(
CallbackType callback,
) {
return _SetCallback(
callback,
);
}
late final _SetCallbackPtr =
_lookup<NativeFunction<Int32 Function(CallbackType)>>(
'SetCallback');
late final _SetCallback =
_SetCallbackPtr.asFunction<int Function(CallbackType)>();
where, typedef CallbackType = Pointer<NativeFunction<Void Function(Uint32)>>;.
What I want to do here is to setup this callback in Dart, pass it to the FFI, essentially using it as my callback as I would have in C. In my API which abstracts away from FFI code (which means I have a class MyLibrary full of static functions that the user will call directly, which in turn calls functions from an object _nativeLibrary of the class MyNativeLibrary I have created), I have:
static int SetCallback({required CallbackFuncDart callback}) {
Pointer<NativeFunction<CallbackFunc>> pointer = Pointer.fromFunction(callback);
int status = _nativeLibrary.SetCallback(
pointer,
);
if (STATUS_OK != status) {
throw LibLexemeException(status);
}
return status;
}
typedef CallbackFunc = Void Function(Uint32);
typedef CallbackFuncDart = void Function(int);
While the sqlite ffi example states here that
Features which dart:ffi does not support yet:
Callbacks from C back into Dart.
I believe the docs haven't been updated to reflect the changes at the samples here. The samples haven't been very clear due to them not having any C/C++ files, or an idea of how the C functions work. Even so, I think this example contains a segment(last code block) where a Dart function is being passed as a callback which I have replicated in my program. It is not clear to me how this will work but upon trying to compile my program I get:
ERROR: ../lib/library_lexeme.dart:180:74: Error: fromFunction expects a static function as parameter. dart:ffi only supports calling static Dart functions from native code. Closures and tear-offs are not supported because they can capture context.
ERROR: Pointer<NativeFunction<CallbackFunc>> pointer = Pointer.fromFunction(callback);
The short version is that you can't pass your callnback as an argument:
static int SetCallback({required CallbackFuncDart callback}) {
Pointer<NativeFunction<CallbackFunc>> pointer = Pointer.fromFunction(callback); // <-- this isn't considered a static function
It's quite annoying but you must use a static function defined ahead of time for your dart callbacks to be called from C.
Apparently for now only static functions can be passed via ffi. But if you have to access an instance's data and you're sure that the instance exists you can use my workaround. I use a static list to the instances. This is stupid and ugly but it works for me:
class CallbackClass {
static Int8 classCallback(int id) {
final instance = instanceList[id];
return instance.instanceCallback();
}
Int8 instanceCallback() { return instanceId; }
static List<CallbackClass> instanceList = <CallbackClass>[];
late final int instanceId;
CallbackClass {
instanceId = instanceList.length;
instanceList.insert(instanceId, this);
myFFImapping.passCallback(instanceId, Pointer.fromFunction<>(classCallback);)
}
}
I omitted the necessary c code, FFI mapping and casting to correct types for clarity, so it obviously won't compile like this.
I have a class where I want to call a static method to initialize some things. I tried calling it from the global scope, like in this simplified example:
class MyClass{
static bool initialized = false;
static void init(){
initialized = true;
}
}
MyClass.init();
void main() async {
// Do something useful
}
This results in the following errors:
Functions must have an explicit list of parameters
The name 'MyClass' is already defined
What I find a bit odd is that if I make the init() method return something and assign that result to a variable, it works:
class MyClass{
static bool initialized = false;
static bool init(){
initialized = true;
return true;
}
}
bool _dummy = MyClass.init();
void main() async {
// Do something useful
}
Why is this? And is there a better workaround to call a static void method from the global scope?
The reason is that static variables are lazy evaluated in Dart, so they will first get a value the first time they are accessed.
That means that MyClass.init() in:
bool _dummy = MyClass.init();
Is only being executed when something are trying to access the variable _dummy. It also means that the following in global scope:
MyClass.init();
Does not make any sense in Dart since this code are never going to be executed since there are no reference to the code.
The reason for this design can be found described in the Dart Language Specification:
Static variable declarations with an initializing expression are initialized lazily.
The lazy semantics are given because we do not want a language where one tends to define expensive initialization computations, causing long application startup times. This is especially crucial for Dart, which must support the coding of client applications.
https://dart.dev/guides/language/specifications/DartLangSpec-v2.10.pdf
I'm running into a weird issue working with SystemVerilog on DVT. The code snippet in question looks something like this:
class parent;
int A;
function void foo();
A = 5;
endfunction
endclass
class childA extends parent;
function void foo();
bit test_one; //Does not flag as a syntax error.
super.foo();
bit test_two; //Flags as error: Expected endfunction, found bit.
endfunction //Subsequently: Expected endclass, found endfunction
endclass //And lastly: Unexpected token: Endclass
As far as I know it is legal to call any hidden parent function using super. but this behavior is perplexing me. Can someone tell me if this is legal SV syntax? Or if not: What's the reasoning behind this?
It is illegal syntax. All variables in a task or function must be declared before any operation. See IEEE Std 1800-2012 ยง 13 Tasks and functions (subroutines)
Legal syntax is:
function void foo();
bit test_one;
bit test_two;
super.foo();
endfunction
The only exception is a begin-end block in which case the variable can be declared at the top of the begin-end block before any operation (but you can nest begin-end block). This does however limit scope access and may be less readable. So it not a good practice
function void foo();
bit test_one;
super.foo();
begin
bit test_two; // only in scope within this begin-end
begin
bit test_three; // not the same 'test_three' as below, different scope
end
begin
bit test_three; // not the same 'test_three' as above, different scope
end
// both 'test_three's are out of scope
end
// 'test_two' both 'test_three's are out of scope
endfunction
General best practice is to always declare your variables at the top. I prefer adding empty space between variable declarations and operations a visual separator; makes reading and modifying a ascetically easier.
function void foo();
bit test_one;
bit test_two;
super.foo();
endfunction
I want to call one void function into many view controllers so how can i do it? please suggest me some idea.
I think you talking about static function.you have to declare and define that function as static , then you can use that void function without initializing the class in any view contorller. And also declare that static function as public.
static function declaration is this
+(void)functionName:(parametertype)parameter;
I'm trying to use class objects with the Arduino, but I keep running into problems. All I want to do is declare a class and create an object of that class. What would an example be?
On Arduino 1.0, this compiles just fine:
class A
{
public:
int x;
virtual void f() { x=1; }
};
class B : public A
{
public:
int y;
virtual void f() { x=2; }
};
A *a;
B *b;
const int TEST_PIN = 10;
void setup()
{
a=new A();
b=new B();
pinMode(TEST_PIN,OUTPUT);
}
void loop()
{
a->f();
b->f();
digitalWrite(TEST_PIN,(a->x == b->x) ? HIGH : LOW);
}
There is an excellent tutorial on how to create a library for the Arduino platform. A library is basically a class, so it should show you how its all done.
On Arduino you can use classes, but there are a few restrictions:
No new and delete keywords
No exceptions
No libstdc++, hence no standard functions, templates or classes
You also need to make new files for your classes, you can't just declare them in your main sketch. You also will need to close the Arduino IDE when recompiling a library. That is why I use Eclipse as my Arduino IDE.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1230935955 states:
By default, the Arduino IDE and
libraries does not use the operator
new and operator delete. It does
support malloc() and free(). So the
solution is to implement new and
delete operators for yourself, to use
these functions.
Code:
#include <stdlib.h> // for malloc and free
void* operator new(size_t size) { return malloc(size); }
void operator delete(void* ptr) { free(ptr); }
This let's you create objects, e.g.
C* c; // declare variable
c = new C(); // create instance of class C
c->M(); // call method M
delete(c); // free memory
Regards,
tamberg
I created this simple one a while back. The main challenge I had was to create a good build environment - a makefile that would compile and link/deploy everything without having to use the GUI. For the code, here is the header:
class AMLed
{
private:
uint8_t _ledPin;
long _turnOffTime;
public:
AMLed(uint8_t pin);
void setOn();
void setOff();
// Turn the led on for a given amount of time (relies
// on a call to check() in the main loop()).
void setOnForTime(int millis);
void check();
};
And here is the main source
AMLed::AMLed(uint8_t ledPin) : _ledPin(ledPin), _turnOffTime(0)
{
pinMode(_ledPin, OUTPUT);
}
void AMLed::setOn()
{
digitalWrite(_ledPin, HIGH);
}
void AMLed::setOff()
{
digitalWrite(_ledPin, LOW);
}
void AMLed::setOnForTime(int p_millis)
{
_turnOffTime = millis() + p_millis;
setOn();
}
void AMLed::check()
{
if (_turnOffTime != 0 && (millis() > _turnOffTime))
{
_turnOffTime = 0;
setOff();
}
}
It's more prettily formatted here: http://amkimian.blogspot.com/2009/07/trivial-led-class.html
To use, I simply do something like this in the .pde file:
#include "AM_Led.h"
#define TIME_LED 12 // The port for the LED
AMLed test(TIME_LED);
My Webduino library is all based on a C++ class that implements a web server on top of the Arduino Ethernet shield. I defined the whole class in a .h file that any Arduino code can #include. Feel free to look at the code to see how I do it... I ended up just defining it all inline because there's no real reason to separately compile objects with the Arduino IDE.
Can you provide an example of what did not work? As you likely know, the Wiring language is based on C/C++, however, not all of C++ is supported.
Whether you are allowed to create classes in the Wiring IDE, I'm not sure (my first Arduino is in the mail right now). I do know that if you wrote a C++ class, compiled it using AVR-GCC, then loaded it on your Arduino using AVRDUDE, it would work.