Re: Multitasking question: Making a picture viewer, loading lots of images in the background
I'm no threading expert but 1000 - if those indeed are real threads (like, preemptive OS threads) - is wa too many. My understanding is that there's no benefit to creating more than the number of hyperthreads your CPU supports (minus your main thread?). So you'd want a work queue of all the available work/images, and then some reasonable number of threads (4-12 depending on core count / hyperthreading) taking work as they need it from that queue. You should probably be looking at std.parallelism (TaskPool etc) for this. Perhaps somebody can provide a more detailed how-to ...
Multitasking question: Making a picture viewer, loading lots of images in the background
Hi, I'm writing a picture browser program and I'd like to ask for a bit of assistance. My app is basically a Win32 window with an OpenGL surface. Currently I'm able to display a lot of pictures in it. The decompression of the bitmaps take place at the beginning of the program. I want to make this more user friendly, so at first I only draw placeholders for the pictures while the actual loading and decompression is happening on worker threads. I used std.concurrency.spawn. The parameters are the filename, and an index. After the decompression I let the main thread know about there is a bitmap it should upload to a texture later. I do it using synchronize, it works without error and was really easy to implements in D. My problem is that when I launch 1000 spawn(), the work overload on the main thread is so heavy that the 60FPS timer which is refreshing the windows never can be called. Obviously spawn() is not the right choice for this. In my previous projects I addressed this by creating NumberOfProcessorThreads threads,and locked them on specific ProcessorThreads by using ProcessAffinity, so the main thread has enough time to generate fluid user interface while the other worker threads used 100%CPU for the fastest processing. I also remember that with OPENMP I was also able to lock workers onto specific ProcessorThreads, it also worked fine. But how can I do this elegantly in D? Thanks in advance! (Also I'm not sure how spaw()-n is working exactly. Is it creates a new process for every spawn() call, or is it assigns the task to one of the N worker processes? 1000 CreateProcess() api calls would be not so nice. I just wanna know it in order to avoid it.)
Re: Access outer member of struct from inner struct
On Tuesday, 2 April 2019 at 18:52:07 UTC, Jacob Carlborg wrote: On 2019-04-02 20:44, Q. Schroll wrote: After removing the calls to writeln, the error I get is: `this` for `read` needs to be type `Outer` not type `Inner` You cannot access stuff in Outer because Inner objects are not outer objects and don't implicitly own an Outer object. In your Inner method `write`, there is no Outer object present at all to call the method on. It works if the struct is nested inside a function [1]. I thought it would work nested inside a struct too. [1] https://dlang.org/spec/struct.html#nested The reason it works inside a function is that the struct has a hidden pointer to the function context. The function's local values actually exist when an object of that struct type is being instantiated. The main difference between a struct nested in a function and one inside another struct is that the one in a function cannot¹ be created outside of that function while constructing the latter is possible the way you think it is: Outer.Inner innerObj = Outer.Inner(parameters); ¹ You can using reflection and stuff like that, but it's still broken if it uses the context.
Re: Access outer member of struct from inner struct
On 2019-04-02 20:44, Q. Schroll wrote: After removing the calls to writeln, the error I get is: `this` for `read` needs to be type `Outer` not type `Inner` You cannot access stuff in Outer because Inner objects are not outer objects and don't implicitly own an Outer object. In your Inner method `write`, there is no Outer object present at all to call the method on. It works if the struct is nested inside a function [1]. I thought it would work nested inside a struct too. [1] https://dlang.org/spec/struct.html#nested -- /Jacob Carlborg
Re: Get attributes of a field?
On 2019-04-02 15:23, Alex wrote:
__traits(getAttributes, T)
Requires a type and a field is unfortunately not a type ;/
enum attr;
struct Foo
{
@attr int a;
}
void main()
{
alias a = __traits(getAttributes, Foo.a);
}
--
/Jacob Carlborg
Re: Get mangled name of field?
On 2019-04-02 15:11, Alex wrote:
How do I get the mangled name of a field? mangledName!T requires passing
a type ;/
struct Foo
{
int a;
}
void main()
{
writeln(Foo.a.mangleof);
}
--
/Jacob Carlborg
Re: Access outer member of struct from inner struct
On Tuesday, 2 April 2019 at 18:20:09 UTC, Andrey wrote:
Hello,
In this example how can I access the members "read" and "q" of
struct Outer from Inner struct?
struct Outer
{
ulong q = 1;
Inner inner;
void read(ulong value)
{
q += value;
}
void run()
{
q.writeln;
read(5);
}
struct Inner
{
void write(string text)
{
read(text.length);
writeln(q);
}
}
}
void main()
{
Outer ttt;
ttt.run();
}
During compilation I get:
onlineapp.d(55): Error: this for read needs to be type Outer
not type Inner
onlineapp.d(56): Error: need this for q of type ulong
After removing the calls to writeln, the error I get is:
`this` for `read` needs to be type `Outer` not type `Inner`
You cannot access stuff in Outer because Inner objects are not
outer objects and don't implicitly own an Outer object. In your
Inner method `write`, there is no Outer object present at all to
call the method on.
Re: gtkDcoding Blog Post for 2019-03-29 - Grid
On 02-04-2019 17:48, Ron Tarrant wrote: On Tuesday, 2 April 2019 at 14:13:09 UTC, number wrote: Can somebody explain why getRgba() (apparently inherited from ColorChooser) does take an out parameter instead of returning an Gdk.RGBA? My understanding is this: Returning an object (as opposed to a single value) means returning a pointer rather than the entire object. And the object will cease to exist once the function returns because the scope no longer exists. So, it follows that an out variable passed in will preserve the object itself once program control returns to the caller. While that would be true for things that live on the stack, this is not the case for RGBA. The C version of getRgba uses the "out" parameter so you can pass in a existing GdkRgba, even tough that would make it more like ref. This doesn't make sense for the d binding since you will always get a new RGBA passed through the out parameter. -- Mike Wey
Access outer member of struct from inner struct
Hello,
In this example how can I access the members "read" and "q" of
struct Outer from Inner struct?
struct Outer
{
ulong q = 1;
Inner inner;
void read(ulong value)
{
q += value;
}
void run()
{
q.writeln;
read(5);
}
struct Inner
{
void write(string text)
{
read(text.length);
writeln(q);
}
}
}
void main()
{
Outer ttt;
ttt.run();
}
During compilation I get:
onlineapp.d(55): Error: this for read needs to be type Outer
not type Inner
onlineapp.d(56): Error: need this for q of type ulong
Re: gtkDcoding Blog Post for 2019-03-29 - Grid
On Tuesday, 2 April 2019 at 14:13:09 UTC, number wrote: Thank you! You're welcome. :) The function ignores its argument and always uses member variable button2 instead. Changing the parameter type to MyRadioButton and using 'button' instead of 'button2' in the body works, so you could pass another default in RadioBox.this(). Thanks for catching my typos. I gotta stop messing with the code once it's working. :) Fixes are uploaded. Anyway, you can also declare it as a RadioButton and that works, too... as long as the variables inside the function are changed to 'button.' Can somebody explain why getRgba() (apparently inherited from ColorChooser) does take an out parameter instead of returning an Gdk.RGBA? My understanding is this: Returning an object (as opposed to a single value) means returning a pointer rather than the entire object. And the object will cease to exist once the function returns because the scope no longer exists. So, it follows that an out variable passed in will preserve the object itself once program control returns to the caller.
Re: Get attributes of a field?
On Tuesday, 2 April 2019 at 13:36:47 UTC, Alex wrote: On Tuesday, 2 April 2019 at 13:23:37 UTC, Alex wrote: __traits(getAttributes, T) Requires a type and a field is unfortunately not a type ;/ I'd like to be able to get the attributes without having to instantiate the base type because that is problematic and I see no reason why it has to be instantiated to get CT values. Could you provide a full example for this issue and for your other message? That makes it easier to help you Kind regards Andre
Re: gtkDcoding Blog Post for 2019-03-29 - Grid
On Tuesday, 2 April 2019 at 11:31:39 UTC, Ron Tarrant wrote: Today's the day for (yet) another blog post over on gtkDcoding.com and the subjects are: - the RadioButton, and - the ColorButton. You can find it here: http://gtkdcoding.com/2019/04/02/0023-radio-and-color-buttons.html Thank you! But if we want one of the others to be active on start-up, as well as syncing up the observed object, we have to call that button’s setActive(true) function. To simplify this two-step process, I broke it out into its own function, setActiveButton(). The function ignores its argument and always uses member variable button2 instead. Changing the parameter type to MyRadioButton and using 'button' instead of 'button2' in the body works, so you could pass another default in RadioBox.this(). Can somebody explain why getRgba() (apparently inherited from ColorChooser) does take an out parameter instead of returning an Gdk.RGBA?
Re: Get attributes of a field?
On Tuesday, 2 April 2019 at 13:23:37 UTC, Alex wrote: __traits(getAttributes, T) Requires a type and a field is unfortunately not a type ;/ I'd like to be able to get the attributes without having to instantiate the base type because that is problematic and I see no reason why it has to be instantiated to get CT values.
Get attributes of a field?
__traits(getAttributes, T) Requires a type and a field is unfortunately not a type ;/
Get mangled name of field?
How do I get the mangled name of a field? mangledName!T requires passing a type ;/
Re: Forbidding implicit conversions from an enum type to an integer
On Tuesday, 2 April 2019 at 09:37:26 UTC, Per Nordlöw wrote: Are there any plans on deprecating implicit conversions of enums to integers? Not that I know of. Given the precedence of this: https://github.com/dlang/DIPs/blob/master/DIPs/rejected/DIP1015.md I doubt enum/integer-types are going to get stricter. Is there a particular bug you encountered because of this conversion?
Re: gtkDcoding Blog Post for 2019-03-29 - Grid
Today's the day for (yet) another blog post over on gtkDcoding.com and the subjects are: - the RadioButton, and - the ColorButton. You can find it here: http://gtkdcoding.com/2019/04/02/0023-radio-and-color-buttons.html
Re: Forbidding implicit conversions from an enum type to an integer
On Tuesday, 2 April 2019 at 09:02:03 UTC, Dennis wrote:
You can make the enum type not an integer type.
```
struct Int{int i;}
enum E: Int {
first = Int(0),
second = Int(1),
}
```
Thanks.
Are there any plans on deprecating implicit conversions of enums
to integers?
Re: Pass template parameter into q{} string
On Monday, 1 April 2019 at 17:32:29 UTC, Andrey wrote:
Hello,
enum Key : string
{
First = "qwerty",
Last = "zaqy"
}
void main()
{
enum decl(alias values1) = q{
static foreach(value; values1)
mixin("bool " ~ value ~ " = false;");
};
enum qqq = [Key.First, Key.Last];
mixin(decl!qqq);
}
I don't understand how to pass template parameter "values1"
into q{} string to get this output:
static foreach(value; [Key.First, Key.Last])
mixin("bool " ~ value ~ " = false;");
or
static foreach(value; qqq)
mixin("bool " ~ value ~ " = false;");
A token string (q{}) is still a string literal[1] (but has
autocomplete on individual tokens in many IDEs). It does not
substitute the text for the values. As such, you'd need to format
the string like usual. The following code worked:
enum Key : string
{
First = "qwerty",
Last = "zaqy"
}
void main()
{
import std.format;
enum decl(alias values1) = q{
static foreach(value; %s)
mixin("bool " ~ value ~ " = false;");
}.format(values1.stringof);
enum qqq = [Key.First, Key.Last];
mixin(decl!qqq);
import std.stdio;
writeln(qwerty);
}
Here we use the format function from the standard library. We
have a format token (%s) in the original string, and replace it
with `values1.stringof`. `.stringof` in this case means the
original text used in the call site passed to argument values1
("qqq"). (When we don't use `.stringof`, "First" and "Last" are
not defined, as the compiler thinks qqq is an array of Keys
instead of strings.)
You could also use a string interpolation library (e.g. [2]) from
Dub.
[1] https://dlang.org/spec/lex.html#token_strings
[2] http://code.dlang.org/packages/stri
Re: Forbidding implicit conversions from an enum type to an integer
On Tuesday, 2 April 2019 at 08:38:28 UTC, Per Nordlöw wrote:
Is there a way (compiler flag) to forbid implicit conversions
from an enum type to integer types?
You can make the enum type not an integer type.
```
struct Int{int i;}
enum E: Int {
first = Int(0),
second = Int(1),
}
```
Forbidding implicit conversions from an enum type to an integer
Is there a way (compiler flag) to forbid implicit conversions from an enum type to integer types?
Re: Build an alias array
On Tuesday, 2 April 2019 at 07:47:29 UTC, Stefan Koch wrote:
On Tuesday, 2 April 2019 at 03:15:36 UTC, Alex wrote:
Is there any way to build an alias array at compile time that
isn't too heavy in resources?
{...}
Hi Alex,
I agree that there should be a way to do that.
As soon as newCTFE is a releasable state, I'll work on that
again :)
I'd be intereseted in your usecases, so I can asses the
requirements better.
Thanks in advance!
- Stefan
I'm just trying to filter out certain types from a static foreach
to use later that are not used immediately. I usually need such a
way to build an sequence though.
static foreach(a; Seq)
{
static if (is(a == S))
{
} else arr.Add(a);
}
The idea is that I can then do
static foreach(a; arr)
{
}
to get the remaining elements.
Sometimes it's just building up up a sequence in some order for
some reason such as collecting types and making decisions between
those types.
Also, sometimes I want to create a hierarchy like a tree but
nodes are sequences.
These things are easy to do at RT but nearly impossible at CT.
With CTFE they can sorta be done but usually one still needs some
way to build a sequence.
I mean, one can easily do this by using different names as I said:
alias arr1 = AliasSeq!(T1);
alias arr2 = AliasSeq!(arr1, T2);
alias arrnp1 = AliasSeq!(arrn, Tn);
but it's difficult to know the final name(well, one can use a
mixin) and it has problems with scoping on static if's. The only
point of doing it is because we can't reassign to an alias.
alias arr = AliasSeq!Empty;
static foreach(Tk; S)
{{
alias arr = AliasSeq!(arr, Tk);
}}
Then arr == S after the loop.
would be ideal.
Re: Build an alias array
On Tuesday, 2 April 2019 at 03:15:36 UTC, Alex wrote:
Is there any way to build an alias array at compile time that
isn't too heavy in resources?
{...}
Hi Alex,
I agree that there should be a way to do that.
As soon as newCTFE is a releasable state, I'll work on that again
:)
I'd be intereseted in your usecases, so I can asses the
requirements better.
Thanks in advance!
- Stefan
