Generic (void *)int
Giuseppe Barbieri
elect86 at gmail.com
Tue Feb 19 07:17:38 UTC 2019
Ok, so first of all, thanks for your effort into this project
Tthis is something extremely cool that I wished we had already from some
time
JNI is quite tedious to work with (sorry), and on the other side JNA is
easier but can be quite slower for some applications.
JNA is, however, nowhere so immediate and fast as using jextractor,
actually is extremely verbose..
Coming back to feedback and observation, I think it's kind of critical to
understand exactly how shall `Scope` be used, which is the general strategy
to follow.
Because I see a couple of options here (which are not ortogonal with each
other, a combination may be possible):
- create a scope every method where you need allocation
- global scope for the whole project (and re-use all you can)
- class scope
- [3d real-time graphics or other performance critical app] (create it once
per frame and) pass it down the line
Also, what about multithreading? How Scope interact with that/which
properties has in this regard?
For example, I can say that GL, AL and CL require a fair amount of native
memory operations.
VK, instead, is another planet: the amount of native structs and other is
massive, each method essentially create some info struct (kind of kotlin
data classes) just to hold a lot of parameters and then pass them as
argument to some function and retrieve an opaque object.
How much is going to cost using Scope? Do you have any performance metrics?
Have you considered alternatives ways, such as thread-local/stack
allocations?
One thing I noticed immediately is that there is no possibility to
deallocate pointer and other native resources, other than let the Scope be
GC"ed and with it all the corresponding native resources allocated with, I
guess.
So, this leads me think that the Scope class is supposed to be short lived?
But at the same time I'm afraid this may cause some pressure on the GC
under specific cases. I don't know.
Nevertheless, I'd like to have some way to deallocate objects.
Let's take as an example that hello triangle
In the `init` (constructor) I do need to allocate for example several
resources, some of them can be trashed and freed right at the end of the
constructor, while some other instead shall survive since they are going to
be used in the render method, like the pMVP (to accomodate the matrix) and
the vertexArray (to hold the name).
A little note aside: I tried also to build it from source, I had to
`bash configure --disable-warnings-as-errors`
to avoid treating warnings like errors and it worked. But I don't see any
jextractor under ./build/linux-x86_64-server-release/images/jdk/bin/
Giuseppe
Il giorno lun 18 feb 2019 alle ore 15:33 Maurizio Cimadamore <
maurizio.cimadamore at oracle.com> ha scritto:
> Whohoo!
> Looking forward to the feedback - and thanks for the patience!
>
> Maurizio
> On 18/02/2019 14:30, Giuseppe Barbieri wrote:
>
> Uh, sorry, my bad, you are right,
>
> ptr1.set(Vec3.lenght.L)
>
>
> should have been
>
> ptr1.set(Vec3.size.L)
>
>
> it works flawless! Thanks you all, guys
>
>
> I'll write later a list with some feedbacks to smooth the experience for gl devs
>
>
>
> Il giorno lun 18 feb 2019 alle ore 15:27 Maurizio Cimadamore <
> maurizio.cimadamore at oracle.com> ha scritto:
>
>> Uhm - the code snippet for converting long into pointer is correct; I
>> checked this on my machine:
>>
>> class Test {
>> public static void main(String[] args) throws Throwable {
>> try (Scope sc = Scope.globalScope().fork()) {
>> var ptr1 = sc.allocate(NativeTypes.LONG);
>> ptr1.set(42L);
>> var p1 =
>> ptr1.cast(NativeTypes.VOID).cast(NativeTypes.VOID.pointer()).get();
>> System.err.println(p1.addr());
>> }
>> }
>> }
>>
>>
>> And this prints 42 as expected.
>>
>> Are you sure the problem is coming from that pointer, and not from
>> somewhere else?
>>
>> Maurizio
>>
>> On 18/02/2019 14:16, Giuseppe Barbieri wrote:
>> > I just had a chance to try, but that, unfortunately, doesnt seem to
>> work..
>> >
>> https://github.com/elect86/panama/blob/master/src/test/kotlin/hello-triangle.kt#L100-L102
>> >
>> > I get a black triangle (I shall get a colored one instead)
>> >
>> > I guess I get at least the vertex positions (the triangle, although
>> black,
>> > is there) because in my case `semantic.attr.POSITION` is luckily zero,
>> > which is the same index where the attributes start from.
>> >
>> > Other ideas?
>> >
>> > Il giorno lun 18 feb 2019 alle ore 10:56 Jorn Vernee <
>> jbvernee at xs4all.nl>
>> > ha scritto:
>> >
>> >> Hi Giuseppe,
>> >>
>> >> You should be able to use this trick:
>> >>
>> >> long pointerValue = 12L; // e.g.
>> >> Scope scope = Scope.newNativeScope; // or
>> Scope.globalScope().fork()
>> >> depending on which version you are
>> >> Pointer<Long> ptr = scope.allocate(NativeTypes.UINT64);
>> >> ptr.set(pointerValue);
>> >> Pointer<?> result =
>> >> ptr.cast(NativeTypes.VOID).cast(NativeTypes.VOID.pointer()).get();
>> >> // use 'result'
>> >>
>> >> Be aware that this does do an allocation of a 64 bit int, so you might
>> >> want to reuse the allocated space if you create a lot of pointers from
>> >> literals.
>> >>
>> >> Maybe in the future we can add an API for creating pointers from long
>> >> literals directly.
>> >>
>> >> Jorn
>> >>
>> >> Giuseppe Barbieri schreef op 2019-02-18 10:44:
>> >>> Thanks Sundar,
>> >>>
>> >>> that works flawless for `(void *)0`
>> >>>
>> >>> But now I also would need a generic solution, for example:
>> >>>
>> >>> (void *)12
>> >>>
>> >>> There is a sill opengl call ( glVertexPointer ) requesting explicitely
>> >>> that: https://stackoverflow.com/a/8283855/1047713
>> >>>
>> >>> Signature:
>> >>>
>> >>> void glVertexAttribPointer(int index, int size, int type, byte
>> >>> normalized, int stride, Pointer<?> pointer);
>> >>>
>> >>>
>> >>> is there actually a way?
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>>
>> >>> You can use Pointer.nullPointer() method.
>> >>>
>> >>> -Sundar
>> >>>
>> >>> On 18/02/19, 8:09 AM, Giuseppe Barbieri wrote:
>> >>>> Hi,
>> >>>>
>> >>>> I'm looking for a way to convert this:
>> >>>>
>> >>>> (void*)0
>> >>>>
>> >>>> in Java.
>> >>>>
>> >>>> I tried to allocate a pointer and set its value to 0, but it didnt
>> >>>> work
>> >>>>
>> >>>> Any ideas, guys?
>> >>>>
>> >>>> Thanks in advance
>>
>
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