Re: Speed of Random Numbers
Thank you very much to Everybody! Giovanni
Where to put custom ldc2.conf (Windows)
Perhaps I posted this to the wrong forum. Help needed. https://forum.dlang.org/post/pdqfquklkhambfccg...@forum.dlang.org
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria
wrote:
For me the "goodness of random" is NOT important.
If that's the case, you could roll your own RNG:
//DMD64 D Compiler 2.072.2
import std.stdio;
import std.datetime;
import std.array, std.random;
void main(){
ubyte x;
auto r = benchmark!(f1,f2)(10_000);
writeln(r[0]);
writeln(r[1]);
}
int f1(){
static s = 10; // Seed
s = (214013*s+2531011); // [1]
s = (s>>16)&0x7FFF;
auto y=(s&7)+1;
//writeln(y);
return y;
}
int f2(){
byte c;
c=uniform!ubyte() % 8 +1;
//writeln(c);
return c;
}
/*
[1]
https://software.intel.com/en-us/articles/fast-random-number-generator-on-the-intel-pentiumr-4-processor/
*/
/*
OUTPUT:
TickDuration(65263) <-f1
TickDuration(635167) <-f2
*/
Matheus.
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 17:47:46 UTC, Giovanni Di Maria
wrote:
On Saturday, 3 August 2019 at 17:44:44 UTC, lithium iodate
wrote:
On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria
wrote:
[...]
First off you could try to use a faster RNG engine than the
default. The easiest way is to define a variable containing it
and passing it to the functions each time.
auto rng = Xorshift(1234);
randomNumber = uniform!uint(rng);
This basic change approximately halved the 5 seconds your
original example needs on my computer.
Another simple approach that I have tried is simply hashing
the iterator using a fast hash function.
With xxHash32 I got the time down to 0.25 seconds. I also
tried xxHash64 and FNV1a but they were not faster in my quick
test.
Thank you very much Lithium Iodate
Now i will try it.
I let know you.
Thank you
Giovanni
If it doesn't matter if it's predictable or not then you could
easily make your own simple random generator with would give
"random" results.
Of course in general it's not usable:
import std.stdio;
class Random
{
private:
uint _seed;
uint _interval;
T abs(T)(T x)
{
T y = x > 0 ? T.max : cast(T)0;
return (x ^ y) - y;
}
public:
this()
{
import core.stdc.time;
_seed = cast(uint)time(null);
_interval = (_seed - 20559);
}
T next(T)(T max)
{
auto value = cast(T)(abs(_interval) % T.max);
_interval -= (_interval / 10) * _seed;
return value;
}
}
void main()
{
auto random = new Random;
foreach (_; 0 .. 1000)
{
auto result = random.next!ubyte(255);
writeln(result);
}
}
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria
wrote:
Do you know other faster functions or methods to generate
random numbers?
For me the "goodness of random" is NOT important.
I found some nice random functions in this public-domain C
single-header library collection, one of which is GameRand:
https://github.com/mattiasgustavsson/libs/blob/022370a79cf2d5f87fb43b420834a069adb5fede/rnd.h#L449
Here's the D version:
```
struct GameRand
{
uint[2] state;
}
uint randomGameRand(ref GameRand gamerand) {
gamerand.state[0] = ( gamerand.state[0] << 16 ) + (
gamerand.state[0] >> 16 );
gamerand.state[0] += gamerand.state[1];
gamerand.state[1] += gamerand.state[0];
return gamerand.state[0];
}
```
It's really fast and decent enough for games (hence the name I
suppose). See:
http://www.flipcode.com/archives/07-15-2002.shtml
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 17:44:44 UTC, lithium iodate wrote: On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria wrote: [...] First off you could try to use a faster RNG engine than the default. The easiest way is to define a variable containing it and passing it to the functions each time. auto rng = Xorshift(1234); randomNumber = uniform!uint(rng); This basic change approximately halved the 5 seconds your original example needs on my computer. Another simple approach that I have tried is simply hashing the iterator using a fast hash function. With xxHash32 I got the time down to 0.25 seconds. I also tried xxHash64 and FNV1a but they were not faster in my quick test. Thank you very much Lithium Iodate Now i will try it. I let know you. Thank you Giovanni
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria wrote: Do you know other faster functions or methods to generate random numbers? For me the "goodness of random" is NOT important. Thank you very much GIovanni Di Maria First off you could try to use a faster RNG engine than the default. The easiest way is to define a variable containing it and passing it to the functions each time. auto rng = Xorshift(1234); randomNumber = uniform!uint(rng); This basic change approximately halved the 5 seconds your original example needs on my computer. Another simple approach that I have tried is simply hashing the iterator using a fast hash function. With xxHash32 I got the time down to 0.25 seconds. I also tried xxHash64 and FNV1a but they were not faster in my quick test.
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 17:17:23 UTC, Cym13 wrote: On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria wrote: [...] To what extent isn't the quality of randomness important to you? Your posts reminds me of the way Doom (the original) did it for things like enemy behaviour and shot dispersion: they generated a static table of 256 random numbers once and any time they needed a random byte they just picked the next in the table. They didn't have any security or sciency concern and just wanted to provide a different game each time so that worked well for them. You won't find anything faster than that I think. Exactly Cym13. The important is to get a different number Ok, thank you. G
Re: Speed of Random Numbers
On Saturday, 3 August 2019 at 16:35:34 UTC, Giovanni Di Maria
wrote:
Hi to everybody
I am doing some experiments about random numbers.
I need "extreme speed" for the generation for numbers from 1 to
8.
Generating 500_000_000 numbers with this code:
-
import std.stdio, std.array, std.random;
void main()
{
byte c;
writeln("Start");
for(int k=1;k<=500_000_000;k++)
c=uniform!ubyte() % 8 +1; //<<< === RANDOM
writeln("Stop");
}
-
I get these results:
c=uniform!ubyte() % 8 +1; ==>>> Execution time: 15.563 s
c=cast(byte)uniform(1, 9); ==>>> Execution time: 24.218 s
Do you know other faster functions or methods to generate
random numbers?
For me the "goodness of random" is NOT important.
Thank you very much
GIovanni Di Maria
To what extent isn't the quality of randomness important to you?
Your posts reminds me of the way Doom (the original) did it for
things like enemy behaviour and shot dispersion: they generated a
static table of 256 random numbers once and any time they needed
a random byte they just picked the next in the table. They didn't
have any security or sciency concern and just wanted to provide a
different game each time so that worked well for them. You won't
find anything faster than that I think.
Speed of Random Numbers
Hi to everybody
I am doing some experiments about random numbers.
I need "extreme speed" for the generation for numbers from 1 to 8.
Generating 500_000_000 numbers with this code:
-
import std.stdio, std.array, std.random;
void main()
{
byte c;
writeln("Start");
for(int k=1;k<=500_000_000;k++)
c=uniform!ubyte() % 8 +1; //<<< === RANDOM
writeln("Stop");
}
-
I get these results:
c=uniform!ubyte() % 8 +1; ==>>> Execution time: 15.563 s
c=cast(byte)uniform(1, 9); ==>>> Execution time: 24.218 s
Do you know other faster functions or methods to generate random
numbers?
For me the "goodness of random" is NOT important.
Thank you very much
GIovanni Di Maria
Re: How to get name of my application (project)
On Saturday, August 3, 2019 5:47:33 AM MDT Rémy Mouëza via Digitalmars-d- learn wrote: > On Saturday, 3 August 2019 at 09:26:03 UTC, Andrey wrote: > > Hello, how to get name of my application (project) that we > > write in dub.json? Is there any compile-time constant like > > __MODULE__? > > If I understand the question correctly, you are looking for > std.file.thisExePath: > - http://dpldocs.info/experimental-docs/std.file.thisExePath.html > - https://dlang.org/phobos/std_file.html#thisExePath Also, the first element in the array passed to main is the name of the executable. - Jonathan M Davis
Re: 1 new
On Friday, 2 August 2019 at 18:25:28 UTC, jmh530 wrote: When I navigate to https://forum.dlang.org/ I have a message that says "1 new reply" to "your posts." Normally, I click on that "1 new reply" and find the post that's new, go to it, and the message disappears. However, it doesn't seem to go away anymore. I tried looking at many different old posts without luck. At one point it was up to "2 new replies," but I viewed that other post and it went back down to "1 new reply." Does anyone else have this? I always have “2 new replies” on that page, no matter how often I take a look. The feature seems a bit broken to me. Bastiaan.
Re: How to get name of my application (project)
On 8/3/19 5:26 AM, Andrey wrote: Hello, how to get name of my application (project) that we write in dub.json? Is there any compile-time constant like __MODULE__? Dear Andrey: Perhaps this is similar to what you are looking for: https://dlang.org/spec/grammar.html#SpecialKeyword SpecialKeyword: __FILE__ __FILE_FULL_PATH__ __MODULE__ __LINE__ __FUNCTION__ __PRETTY_FUNCTION__ These are available at compile time. Kind regards.
Re: How to get name of my application (project)
03.08.2019 12:26, Andrey пишет: Hello, how to get name of my application (project) that we write in dub.json? Is there any compile-time constant like __MODULE__? You can get it using $DUB_PACKAGE from Environment variables (https://dub.pm/package-format-sdl), for example using preBuildCommands you can generate a module and define the constant you need there.
Re: Can one customize unit tests?
The out-of-the box unittest runner is pretty bare by design. It
just runs unittest blocks in serial as functions where assert()
failures are not undefined behavior. Assert messages are not very
helpful, though the recently added flag `-checkaction=context`
helps a lot.
Luckily there is a trait for getting unittests:
https://dlang.org/spec/traits.html#getUnitTests
So it is possible to make your own unittest runner, as people
have done:
http://code.dlang.org/packages/silly
http://code.dlang.org/packages/unit-threaded
http://code.dlang.org/packages/dunit
On Saturday, 3 August 2019 at 13:31:02 UTC, PV wrote:
Is it possible to somehow customize syntax and running of unit
tests?
You can add @("attributes") to your unittests.
The default test-runner will not do anything with them currently,
but your own test runner can.
I'd looked into the documentation, found nothing, but perhaps I
just missed it. If it is not possible, is it realistic to (very
easily) hack the D compiler to implement such feature?
Shouldn't be necessary, I think what you want can be done with
attributes and your own test runner.
Would such feature also work in betterC?
unittest blocks itself are supported in betterC, so you can
probably make it work.
Can one customize unit tests?
Is it possible to somehow customize syntax and running of unit
tests?
How I could use it:
1. Running only the tests from recently modified source files.
2. Ability to add optional timeout constraint into the tests, and
then check whether the test doesn't exceed it.
unittests (time < 20 ms) { ... }
3. Checking that tests do not leak memory (where applicable).
4. Invoking tests in both D code and in C, where similar
framework exists.
I'd looked into the documentation, found nothing, but perhaps I
just missed it. If it is not possible, is it realistic to (very
easily) hack the D compiler to implement such feature?
Would such feature also work in betterC?
Re: How to get name of my application (project)
On Saturday, 3 August 2019 at 09:26:03 UTC, Andrey wrote: Hello, how to get name of my application (project) that we write in dub.json? Is there any compile-time constant like __MODULE__? The name of an application is not a compile time constant: you can rename the executable at any time. Like Rémy said, thisExePath.baseName will get you the name at run time. Bastiaan.
Re: Help me decide D or C
On Fri, 2019-08-02 at 20:24 +, Jon Degenhardt via Digitalmars-d-learn wrote: […] > In my view, the most important thing is the decision you've > already made - to pick a programming language and learn it in a > reasonable bit of depth. Which programming language you choose is > less important. No matter which choice you make you'll have the > opportunity to learn skills that will transfer to other > programming languages. > […] Knowing what a given programming language is best for is core here: so no using Prolog to try and write an operating system on real hardware. Knowing many paradigms well is proven experimentally (see the work by Petre, Green, Gilmore, and others) to improve capability in any given language. So knowing Java, Prolog, Lisp, Python, SQL, C, Go, Rust, D, Kotlin, Groovy, Ruby to a goodly level of competence makes you a better programmer in any one of them. So no matter which language you learn always plan to learn others. In this sense C and D are equal, but for applications I'd choose D over C. -- Russel. === Dr Russel Winder t: +44 20 7585 2200 41 Buckmaster Roadm: +44 7770 465 077 London SW11 1EN, UK w: www.russel.org.uk signature.asc Description: This is a digitally signed message part
Re: [OT] Re: Using Haskell for teaching [was: Help me decide D or C]
On Fri, 2019-08-02 at 23:24 -0600, Jonathan M Davis via Digitalmars-d-learn wrote: […] > The university I went to had an undergrad class on programming paradigms > that I _think_ was required (maybe two even), but it was definitely just the > focus of a small number of classes, whereas my experience is that you get a > lot more out of it when you actually use a language with a different > paradigm for a while rather than just doing one group of assignments in it - > and when the class covers multiple programming paradigms, that also dilutes > how much you get out of each. On some level, as with many things, a lot of > it depends on how much the students decide to put into it on their own. […] UCL used to have a 10 week module that tried to do three language to show that different programming languages were best for different problems. Prolog, Snobol, and ??? were the trio when we terminated the module as not being effective. This reinforced having a third programming language module in the compulsory programming sequence so as to have 10 weeks per language rather than three. Still not really long enough but it worked a lot better. I think universities will be far better able to teach programming now that entrants already know Python (to a greater or lesser extent). The single biggest problem will be (has always been) having academics on the staff competent and willing to put on programming courses. Far too many academics in universities are truly crap programmers and are the last people you want to show their crapness to students. -- Russel. === Dr Russel Winder t: +44 20 7585 2200 41 Buckmaster Roadm: +44 7770 465 077 London SW11 1EN, UK w: www.russel.org.uk signature.asc Description: This is a digitally signed message part
Re: Help me decide D or C
On Fri, 2019-08-02 at 16:49 +, Alexandre via Digitalmars-d-learn wrote: […] > > Do you thing D would be the right tool for the job at this point > for me? Assuming I have 2 goals in mind: 1) become a better > programmer and 2) want to make fun writing software for myself > and if possible show something I might be proud of. > I thought C would be a better choice for the 1), because everyone > says it's great to see whats behind the hood and things like > that. My experience with C btw is CS50 course, plus around > 200/300 pages of some books, still reading and a few toy > projects. So, basically 0 knowledge. haha. But after reading your > opinion, I guess C might not be the right tool for me, since I > wont be doing any kind of thing related to hardware (I think). Seeing what is behind the hood was important in the 1970s and 1980s because the hardware was constrained and programming languages (other than perhaps Lisp) were still trying to provide abstractions over the extant hardware. In the 2000s and 2010s "seeing what is under the hood" is more or less irrelevant for most applications programmers – this does not include people for whom hard real time factors are critical to their software. Most application programmers should be focusing on using the right algorithms and data structures for the task and letting the compilers and their code generators worry about what is "under the hood". Programming for microcontrollers is a different game and C dominates there still (I assume, it is over a decade since I was doing that stuff), and for good reason, the algorithms and data structures are hardware oriented rather than being abstract. And when your hardware has bit data structures, so does your programming language: C compilers for 8051 and AVR chips have special extensions to allow bit access. As for your 2, what do you find fun to create software for? It is then a question of choosing the language that best enables you to simply and easily create the data structures and thence the algorithms for those problems. Being able to show off software and be proud of it revolves around having the simplest and most understandable expressions of the best data structures and algorithms for the problem addressed. C can be used for this but you end up hacking this very badly, and opening yourself up to horrors such as buffer overrun. My pet project of the moment is a DVB player (Me TV). It was originally a C program authored by someone else who then began transforming it to a mixed C/C++ system. It's original goal was to compete with MythTV and Kodi, but it lost. When I picked it up I decided to strip it all back so as to be a lightweight player to complement rather than compete with MythTV and Kodi. It became very clear, very quickly that C++11 and indeed C++14 were not the right tools for the job (poor support for messaging between threads being the single biggest problem). I decided to do a re-write from scratch in D using GtkD and GStreamerD. It all went well, D provided all the tools for creating the right abstractions; the right data structures and algorithms were easy to express and the libraries gave really good access to the underlying C libraries. But… the GStreamer folk had rejected D as an officially supported language for plugins and official API wrapper/binding support. Does this matter given Mike's efforts keeping GtkD and GStreamerD up to date? In my case yes. I had to get involved in amendments to GStreamer itself and developing new API wrapper. I guess I could have kept going with D as the implementation language for Me TV, but it seemed right to switch to Rust, which is officially supported by the GStreamer folk, so lots of extra support for GStreamer changes and wrapper writing (I guess I will end up doing a D version for Mike to add to GStreamerD). It turns out that Rust is actually the wrong tool for the job of working with GObject systems and yet the GStreamer folk chose Rust because they abhorred C++ and assumed D always came with a garbage collector (which is true in this case) and they have a morbid hatred of garbage collection (true for some bits of GStreamer which are hard real time). What the gtk-rs people have done though is to provide an excellent (albeit not totally complete as yet) Rust inheritance system for GObject-based code. Of course D has inheritance and so no problem, D is better than Rust for this. Objectively D is the better language for GObject-based software, and yet Rust is in the driving seat. Is this another "everyone used C for applications programming but shouldn't have done" moment? Almost. Rust is fine for those cases where composition is the right abstraction approach. D can also do this, ditto Go, and indeed Java, Kotlin, etc. Where a core abstraction requirement is inheritance, as in GObject-based systems, D beats Rust. And yet the gtk-rs folk have used Rust anyway and created the abstractions. What is the moral behind this story of mixed messa
Re: How to get name of my application (project)
On Saturday, 3 August 2019 at 09:26:03 UTC, Andrey wrote: Hello, how to get name of my application (project) that we write in dub.json? Is there any compile-time constant like __MODULE__? If I understand the question correctly, you are looking for std.file.thisExePath: - http://dpldocs.info/experimental-docs/std.file.thisExePath.html - https://dlang.org/phobos/std_file.html#thisExePath
Re: Help me decide D or C
On Fri, 2019-08-02 at 17:25 +, berni via Digitalmars-d-learn wrote: > […] > > Yes, that was intentional. What I wanted to say is, that I think, > that it would have been better, if C was never invented at all... > In that case, there would have been space for an other language > for writing operating systems, without that much bugs in its > design. (But one never knows afterwards...) If C had not been invented by Ritchie, Thompson, et al., something very like it would have been invented by someone else. BCPL and B were not really gaining the traction they perhaps should have had, and Algol, Algol68, FORTRAN, PL/1, COBOL, etc. were not really designed for writing operating systems. https://en.wikipedia.org/wiki/Timeline_of_programming_languages The problem was not the invention of C, the problem was all those programmers who stopped thinking about using the right tool for a given task in a given context, and started using C for all programming situations. But it happened, it is read-only history. Rust, D, and Go are the current ways out of the tragedy that was using C for applications programming. C++ is finally catching up. -- Russel. === Dr Russel Winder t: +44 20 7585 2200 41 Buckmaster Roadm: +44 7770 465 077 London SW11 1EN, UK w: www.russel.org.uk signature.asc Description: This is a digitally signed message part
Re: Can I remove an element from a global associative array from within a class destructor?
On Friday, 2 August 2019 at 23:13:10 UTC, realhet wrote: Today I read the documentation about structs, unions and classes, but I haven't find any restrictions for the ~this() destructors. Is there some extra rules regarding the GC and what I must not do in the destructors? Class destructors are similar to Java's finalizers in behavior. D doesn't give you a guarantee when the class destructor is called and it doesn't give you a guarantee if it will be called at all, so it doesn't really work for RAII-like resource management. If you want RAII-like behavior, either use structs (struct destructors are deterministic), or wrap your class inside a scoped/refCounted wrapper from std.typecons.
How to get name of my application (project)
Hello, how to get name of my application (project) that we write in dub.json? Is there any compile-time constant like __MODULE__?
Re: Can I remove an element from a global associative array from within a class destructor?
On Saturday, 3 August 2019 at 05:33:05 UTC, Jonathan M Davis wrote: On Friday, August 2, 2019 5:13:10 PM MDT realhet via Digitalmars-d-learn wrote: Hi, ... Thank you! Now I have 2 solutions in mind: 1. If I only want to track the count and totalBytes for a specific kind of reference, I will be able update those from the destructor. 2. If I wanna track all instances of resources, I will use 2 classes instead of one class and an associative array: - When I create a resource, I create class1 for the statistics, and store them in an assocArray. Then I create a class2 and inside it there is a reference to class1. Class2 will be given to the user. If the user don't use it anymore, the GC will destroy class2, and in it's destructor it will mark a field in class1. And it will be periodically checked, so the actual deletion of the GLBuffer and other statistics will be done by me. With millions of resources it will be slow, but for a few thousand it's ok. (I can also put them in a hierarchy, but the most important is not to alloc/dealloc from ~this()) I hope it will be stable :D Thank You again!
