Quick int pointer allocation question
This is going to be quick: Is it possible to allocate and initialize an int in the same line? int* p = new int(5); I haven't found a way to 1 liner it. Is it possible? Do I have to two liner it? int* p = new int(); *p = 5; Thanks.
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 09:20:03 UTC, monarch_dodra wrote: This is going to be quick: Is it possible to allocate and initialize an int in the same line? int* p = new int(5); I haven't found a way to 1 liner it. Is it possible? Do I have to two liner it? int* p = new int(); *p = 5; Thanks. Or dup a pointer to an int for that matter: int* p1 = ... ; int* p2 = p1.dup; ?
Re: Quick int pointer allocation question
Whilst I'm on the subject of questions, how does one allocate, but bypassing the extra memcpy of T.init? Is this possible? int x = void; http://dpaste.dzfl.pl/24c1baa9
Re: Quick int pointer allocation question
On Friday, September 14, 2012 11:20:16 monarch_dodra wrote: This is going to be quick: Is it possible to allocate and initialize an int in the same line? int* p = new int(5); I haven't found a way to 1 liner it. Is it possible? Nope. Though I think that it should be. Do I have to two liner it? int* p = new int(); *p = 5; Yep. Though I have a pull request which will make it so that you can do auto p = makeNew!int(5); https://github.com/D-Programming-Language/phobos/pull/756 - Jonathan M Davis
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 10:33:47 UTC, David wrote:
Whilst I'm on the subject of questions, how does one allocate,
but
bypassing the extra memcpy of T.init? Is this possible?
int x = void;
http://dpaste.dzfl.pl/24c1baa9
Hum, but that is a stack allocated variable.
What about:
struct S { }
void main()
{
S* ps = new S(void); //? doesn't work
}
On Friday, 14 September 2012 at 10:37:56 UTC, Jonathan M Davis
wrote:
On Friday, September 14, 2012 11:20:16 monarch_dodra wrote:
This is going to be quick: Is it possible to allocate and
initialize an int in the same line?
int* p = new int(5);
I haven't found a way to 1 liner it. Is it possible?
Nope. Though I think that it should be.
Do I have to two liner it?
int* p = new int();
*p = 5;
Yep. Though I have a pull request which will make it so that
you can do
auto p = makeNew!int(5);
https://github.com/D-Programming-Language/phobos/pull/756
- Jonathan M Davis
Thanks. Glad we have a library solution, but that's the kind of
thing that should work out of the box I think.
Re: Quick int pointer allocation question
On 2012-09-14 12:52, monarch_dodra wrote: int x = void; http://dpaste.dzfl.pl/24c1baa9 Hum, but that is a stack allocated variable. Perhaps using GC.malloc? -- /Jacob Carlborg
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 11:17:55 UTC, Jacob Carlborg wrote: On 2012-09-14 12:52, monarch_dodra wrote: int x = void; http://dpaste.dzfl.pl/24c1baa9 Hum, but that is a stack allocated variable. Perhaps using GC.malloc? Hum, apparently, there is a second (default aka-hidden) argument that is a bitmask applied to the allocated memory. So not much gain there. I'm allocating an array of 500_000 ulongs, and afterwards, I'm initializing them all by hand, making the default allocation useless. I'm not going to lose any sleep over this, but there is no way in D to get (garbage collected) un-initialized memory/allocations?
Re: Quick int pointer allocation question
On Fri, 14 Sep 2012 05:20:16 -0400, monarch_dodra monarchdo...@gmail.com wrote: This is going to be quick: Is it possible to allocate and initialize an int in the same line? int* p = new int(5); I haven't found a way to 1 liner it. Is it possible? Do I have to two liner it? int* p = new int(); *p = 5; int *p = [5].ptr; -Steve
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 14:33:51 UTC, Steven Schveighoffer wrote: On Fri, 14 Sep 2012 05:20:16 -0400, monarch_dodra monarchdo...@gmail.com wrote: This is going to be quick: Is it possible to allocate and initialize an int in the same line? int* p = new int(5); I haven't found a way to 1 liner it. Is it possible? Do I have to two liner it? int* p = new int(); *p = 5; int *p = [5].ptr; -Steve Fancy! Thankyou.
Re: Quick int pointer allocation question
monarch_dodra:
int *p = [5].ptr;
-Steve
But see this benchmark:
void main() {
auto pointers = new int*[1_000_000];
foreach (int i, ref p; pointers)
p = [i].ptr;
foreach (i; 0U .. 4_000_000_000U) {}
}
On my 32 bit system its RAM commit is about 23 MB. The pointers
array takes about 4 MB. This means each int takes about 19
bytes of heap RAM instead of 4. Each int allocates some data
(capacity) to extend the array.
Bye,
bearophile
Re: Quick int pointer allocation question
On Fri, 14 Sep 2012 16:27:55 +0200, monarch_dodra monarchdo...@gmail.com wrote: On Friday, 14 September 2012 at 11:17:55 UTC, Jacob Carlborg wrote: On 2012-09-14 12:52, monarch_dodra wrote: int x = void; http://dpaste.dzfl.pl/24c1baa9 Hum, but that is a stack allocated variable. Perhaps using GC.malloc? Hum, apparently, there is a second (default aka-hidden) argument that is a bitmask applied to the allocated memory. So not much gain there. I'm allocating an array of 500_000 ulongs, and afterwards, I'm initializing them all by hand, making the default allocation useless. I'm not going to lose any sleep over this, but there is no way in D to get (garbage collected) un-initialized memory/allocations? What's wrong with GC.malloc? The bitmask is there to... well, many things. Pass it BlkAttr.NO_SCAN to ensure memory is not initialized. I think that's all what's needed. -- Simen
Task management
Hi, can anyone tell me what is the good (for arbitrary low values of good) way to forcibly end a running task? I am using a task pool from std.parallelism to execute delegates supplied by various plugins. As I have no real control over what gets executed and how, there is always a possibility that some plugin hangs for good. This is obviously something that I do not want, so I would like to know whether there is a way to kill such unresponsive task. Thanks, Martin
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 09:20:03 UTC, monarch_dodra wrote:
This is going to be quick: Is it possible to allocate and
initialize an int in the same line?
int* p = new int(5);
I haven't found a way to 1 liner it. Is it possible?
Do I have to two liner it?
int* p = new int();
*p = 5;
Thanks.
Firstly I thought this thread is purely about syntax. However,
after rereading I think it is about problem of allocation on GC
heap without default initialization. If I understood it right,
possible solution is:
struct S
{
ulong[500_000] array = void;
void load(ulong value)
{
foreach (i, ref ulong v; array)
{
array[i] = value;
}
}
}
void main()
{
// int* p = new int, x = ((*p=5) == 5) ? null : null;
// assert(*p == 5);
auto s = new S;
s.load(5);
}
Re: Quick int pointer allocation question
monarch_dodra: I'm allocating an array of 500_000 ulongs, and afterwards, I'm initializing them all by hand, making the default allocation useless. In std.array there are two functions to avoid a double initialization, mostly to be used for nonreference data. Bye, bearophile
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 18:14:54 UTC, bearophile wrote: monarch_dodra: I'm allocating an array of 500_000 ulongs, and afterwards, I'm initializing them all by hand, making the default allocation useless. In std.array there are two functions to avoid a double initialization, mostly to be used for nonreference data. Bye, bearophile http://dlang.org/phobos/std_array.html#uninitializedArray and http://dlang.org/phobos/std_array.html#minimallyInitializedArray
Quick question about new semantics
I have a struct, which defines a constructor that takes an
argument.
Now, I'd like to new this object, to it's default T.init value
(eg call new, but now constructors):
struct S
{
this(int);
}
void main()
{
auto p1 = new S;
auto p2 = new S();
}
main.d(8): Error: constructor main.S.this (int) is not callable
using argument types ()
main.d(8): Error: expected 1 function arguments, not 0
main.d(9): Error: constructor main.S.this (int) is not callable
using argument types ()
main.d(9): Error: expected 1 function arguments, not 0
Is this a bug? If auto a = S(); is legal, how can auto p = new
S(); not be?
Re: Quick int pointer allocation question
On Friday, 14 September 2012 at 14:27:43 UTC, monarch_dodra wrote: On Friday, 14 September 2012 at 11:17:55 UTC, Jacob Carlborg wrote: Perhaps using GC.malloc? Hum, apparently, there is a second (default aka-hidden) argument that is a bitmask applied to the allocated memory. So not much gain there. I'm allocating an array of 500_000 ulongs, and afterwards, I'm initializing them all by hand, making the default allocation useless. I'm not going to lose any sleep over this, but there is no way in D to get (garbage collected) un-initialized memory/allocations? Never mind, I misread the doc. The bitmask is not memcopied, it is actually just a mask of options, so GC works perfectly. Anybody know what the attribute FINALIZE (Finalize the data in this block on collect) means? On Friday, 14 September 2012 at 18:14:54 UTC, bearophile wrote: monarch_dodra: I'm allocating an array of 500_000 ulongs, and afterwards, I'm initializing them all by hand, making the default allocation useless. In std.array there are two functions to avoid a double initialization, mostly to be used for nonreference data. Bye, bearophile I was looking for those actually, but I was looking in std.algorithm... Thanks
Re: Quick int pointer allocation question
On Fri, 14 Sep 2012 13:03:37 -0400, bearophile bearophileh...@lycos.com
wrote:
monarch_dodra:
int *p = [5].ptr;
-Steve
But see this benchmark:
void main() {
auto pointers = new int*[1_000_000];
foreach (int i, ref p; pointers)
p = [i].ptr;
foreach (i; 0U .. 4_000_000_000U) {}
}
On my 32 bit system its RAM commit is about 23 MB. The pointers array
takes about 4 MB. This means each int takes about 19 bytes of heap RAM
instead of 4. Each int allocates some data (capacity) to extend the
array.
That has nothing to do with using array literals -- it has to do with the
fact that the minimum heap block is 16-bytes (or 4 ints wide). Extra 3
bytes is probably for overhead and static data.
If instead of p = [i].ptr; you did p = new int; *p = i;
You would get the same exact behavior.
No way around this, unless you want to do custom allocators.
-Steve
Re: Quick question about new semantics
On Fri, 14 Sep 2012 14:27:56 -0400, monarch_dodra monarchdo...@gmail.com
wrote:
I have a struct, which defines a constructor that takes an argument.
Now, I'd like to new this object, to it's default T.init value (eg call
new, but now constructors):
struct S
{
this(int);
}
void main()
{
auto p1 = new S;
auto p2 = new S();
}
main.d(8): Error: constructor main.S.this (int) is not callable using
argument types ()
main.d(8): Error: expected 1 function arguments, not 0
main.d(9): Error: constructor main.S.this (int) is not callable using
argument types ()
main.d(9): Error: expected 1 function arguments, not 0
Is this a bug? If auto a = S(); is legal, how can auto p = new S();
not be?
It is a bug.
http://d.puremagic.com/issues/show_bug.cgi?id=4247
-Steve
Re: Quick int pointer allocation question
Steven Schveighoffer: it has to do with the fact that the minimum heap block is 16-bytes (or 4 ints wide). Extra 3 bytes is probably for overhead and static data. If instead of p = [i].ptr; you did p = new int; *p = i; You would get the same exact behavior. No way around this, unless you want to do custom allocators. Right, maybe you told me the same thing lot of time ago. Thank you for saying such things again. 16 bytes are a lot, so there's not a lot of point in creating very small trees nodes :-) Bye, bearophile
Re: Quick int pointer allocation question
On Fri, 14 Sep 2012 15:23:40 -0400, monarch_dodra monarchdo...@gmail.com wrote: Anybody know what the attribute FINALIZE (Finalize the data in this block on collect) means? Don't use it. It specifies that the block is a D class instance, and so has a vtable with a finalizer referenced therein. Obviously an int does not have that. -Steve
Re: Quick question about new semantics
On Friday, September 14, 2012 20:27:56 monarch_dodra wrote:
I have a struct, which defines a constructor that takes an
argument.
Now, I'd like to new this object, to it's default T.init value
(eg call new, but now constructors):
struct S
{
this(int);
}
void main()
{
auto p1 = new S;
auto p2 = new S();
}
main.d(8): Error: constructor main.S.this (int) is not callable
using argument types ()
main.d(8): Error: expected 1 function arguments, not 0
main.d(9): Error: constructor main.S.this (int) is not callable
using argument types ()
main.d(9): Error: expected 1 function arguments, not 0
Is this a bug? If auto a = S(); is legal, how can auto p = new
S(); not be?
Presumably, because it takes a different path in the compiler. S() could be
treated as a static opCall (certainly, that's how you define a pseudo-default
constructor on structs), whereas new S() newer would be. However, if anything,
I'm surprised that
auto s = S();
compiles given that other constructors are defined. But I guess that it just
always does S.init. There's also a decent chance that the code related to new
S() is the same for classes which _don't_ have an init value which would ever
be usable with new (and which definitely disallow new S() if there's no default
constructor).
I expect that it's a corner case that simply wasn't thought through, and
arguably it should work. I don't know that the spec says one way or the other
though (my guess is that it's silent on the matter, since it tends to be
fairly sparse). Certainly, without allowing that, constructing an S on the
heap which is S.init is a bit of a pain. It probably requires using either
emplace or taking the pointer to an element in an array (which would waste
memory).
I think that there's certainly an argument for allowing what you're trying to
do.
- Jonathan M Davis
