Hi! Now I have this code :

      auto acelByObjs = map!( (Entity o) {
          Vector3 r = o.pos[0] - pos[0];
          return r * (o.mass / pow((r.sq_length + epsilon2), 1.5));
          } )(objects);
      newAcel = reduce!("a + b")(acelByObjs);

It works very well with the std.algorithm Map and Reduce but when I try to use std.parallelism versions of it, parallel Map give me this compilataion errors :

entity.d(63): Error: template instance map!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
) cannot use local '__lambda3' as parameter to non-global template map(functions...)
/usr/include/dmd/phobos/std/parallelism.d(1969): Error: function std.parallelism.TaskPool.map!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
).map!(Entity[]).map.Map.fillBuf cannot access frame of function entity.Entity.CalcAcel
/usr/include/dmd/phobos/std/parallelism.d(1974): Error: template instance amap!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
) cannot use local '__lambda3' as parameter to non-global template amap(functions...)
/usr/include/dmd/phobos/std/parallelism.d(1675): Error: function std.parallelism.TaskPool.amap!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
).amap!(Entity[],ulong,Vector3[]).amap cannot access frame of function entity.Entity.CalcAcel
/usr/include/dmd/phobos/std/parallelism.d(1706): Error: function std.parallelism.TaskPool.amap!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
).amap!(Entity[],ulong,Vector3[]).amap.doIt cannot access frame of function entity.Entity.CalcAcel
/usr/include/dmd/phobos/std/parallelism.d(1974): Error: template instance std.parallelism.TaskPool.amap!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
).amap!(Entity[],ulong,Vector3[]) error instantiating
entity.d(66):        instantiated from here: map!(Entity[])
entity.d(66): Error: template instance std.parallelism.TaskPool.map!(delegate @system Vector3(Entity o)
{
Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
}
).map!(Entity[]) error instantiating
make: *** [predSim] Error 1

Plus , if  I only the parallel Reduce, It takes more around 9 times more that the serial versión for an array of 30 elements!
I tested before parallel reduction with the example code of calculating PI, in my quad core machine taking 4 times less that the serial versión... I will try with a bigger array but using parallel foreach takes less times that serial versión, so I don't think that the these big extra time comes for making the theads. Any other idea of what can be hapening here ?

On 12/11/2012 02:53 AM, Zardoz wrote:

> auto acelByObjs = map!( (Entity o) {
> Vector3 r = o.pos[0] - pos[0];
> return r * (o.mass / pow((r.sq_length + epsilon2), 1.5));
> } )(objects);
> newAcel = reduce!("a + b")(acelByObjs);
>
> It works very well with the std.algorithm Map and Reduce but when I try
> to use std.parallelism versions of it, parallel Map give me this
> compilataion errors :
>
> entity.d(63): Error: template instance map!(delegate @system
> Vector3(Entity o)
> {
> Vector3 r = o.pos[0LU].opBinary(this.pos[0LU]);
> return r.opBinary(o.mass / pow(r.sq_length() + epsilon2,1.5));
> }
> ) cannot use local '__lambda3' as parameter to non-global template
> map(functions...)

That used to work a couple of dmd versions ago. I think it was a bug that it worked, so it stopped working after bug fixes.

If I'm not mistaken this is actually related to a compiler implementation issue: Lambda's have a single pointer to store the context that they have been started in.

When a lambda is a free-standing function (aka "module function" or "global function") then there is only the context to deal with. When the template is a member function (taskPool.map is) then there is also the object that the function is started on.

The single pointer of the lambda is not sufficient to store both without big changes in the compiler.

(I may be off with that description above. e.g. there may be two pointers when three are actually needed, etc.)

I had to change following chapter after dmd's behavior had changed:

  http://ddili.org/ders/d.en/parallelism.html

--- Quoting ---
import std.parallelism;
// ...
double averageGrade(Student student)
{
    return student.averageGrade;
}
// ...
    auto results = taskPool.map!averageGrade(students, 3);

Note: The free-standing averageGrade() function above is needed due to a limitation that involves using local delegates with member function templates like TaskPool.map:

  auto results = taskPool.map!(a => a.averageGrade)(students, 3); // ← compilation ERROR
----------

As you see above, the solution is to use a function with taskPool.map, not a lambda.

Ali

Ali Çehreli:

> The single pointer of the lambda is not sufficient to store both without big changes in the compiler.

I think adding a heavier 3-word delegate is not too much hard to do. But it makes the language more complex, so so far Walter is not willing to introduce them.

But in the end introducing them may become inevitable :-) I think such hypothetical 3-word delegates need to be discussed in the main D newsgroup.

Bye,
bearophile

On Tuesday, 11 December 2012 at 15:22:49 UTC, Ali Çehreli wrote:
> That used to work a couple of dmd versions ago. I think it was a bug that it worked, so it stopped working after bug fixes.
>
> If I'm not mistaken this is actually related to a compiler implementation issue: Lambda's have a single pointer to store the context that they have been started in.
>
> When a lambda is a free-standing function (aka "module function" or "global function") then there is only the context to deal with. When the template is a member function (taskPool.map is) then there is also the object that the function is started on.
>
> The single pointer of the lambda is not sufficient to store both without big changes in the compiler.
>
> (I may be off with that description above. e.g. there may be two pointers when three are actually needed, etc.)
>
> I had to change following chapter after dmd's behavior had changed:
>
>   http://ddili.org/ders/d.en/parallelism.html
>
> --- Quoting ---
> import std.parallelism;
> // ...
> double averageGrade(Student student)
> {
>     return student.averageGrade;
> }
> // ...
>     auto results = taskPool.map!averageGrade(students, 3);
>
> Note: The free-standing averageGrade() function above is needed due to a limitation that involves using local delegates with member function templates like TaskPool.map:
>
>   auto results = taskPool.map!(a => a.averageGrade)(students, 3); // ← compilation ERROR
> ----------
>
> As you see above, the solution is to use a function with taskPool.map, not a lambda.
>
> Ali

I try to use a function instead of a lambda function I'm keep getting compiler errors. Code :
      Entity MapIntegrator (ref Entity me) {
        me.Integrador3Orden (iDeltaT);
        return me;
      }
      objects = array( taskPool.map!MapIntegrator(objects) );

With taskPool.Map I get this errors :
simulator.d(196): Error: template instance map!(MapIntegrator) cannot use local 'MapIntegrator' as parameter to non-global template map(functions...)
/usr/include/dmd/phobos/std/parallelism.d(1969): Error: function std.parallelism.TaskPool.map!(MapIntegrator).map!(Entity[]).map.Map.fillBuf cannot access frame of function D main
/usr/include/dmd/phobos/std/parallelism.d(1974): Error: template instance amap!(MapIntegrator) cannot use local 'MapIntegrator' as parameter to non-global template amap(functions...)
/usr/include/dmd/phobos/std/parallelism.d(1675): Error: function std.parallelism.TaskPool.amap!(MapIntegrator).amap!(Entity[],ulong,Entity[]).amap cannot access frame of function D main
/usr/include/dmd/phobos/std/parallelism.d(1706): Error: function std.parallelism.TaskPool.amap!(MapIntegrator).amap!(Entity[],ulong,Entity[]).amap.doIt cannot access frame of function D main
/usr/include/dmd/phobos/std/parallelism.d(1974): Error: template instance std.parallelism.TaskPool.amap!(MapIntegrator).amap!(Entity[],ulong,Entity[]) error instantiating
simulator.d(196):        instantiated from here: map!(Entity[])
simulator.d(196): Error: template instance std.parallelism.TaskPool.map!(MapIntegrator).map!(Entity[]) error instantiating
make: *** [predSim] Error 1

But again, with std.algorthim Map it don give any error and works fine.

On 12/11/2012 08:12 AM, Zardoz wrote:

> I try to use a function instead of a lambda function I'm keep getting
> compiler errors. Code :
> Entity MapIntegrator (ref Entity me) {
> me.Integrador3Orden (iDeltaT);
> return me;
> }
> objects = array( taskPool.map!MapIntegrator(objects) );
>
> With taskPool.Map I get this errors :
> simulator.d(196): Error: template instance map!(MapIntegrator) cannot
> use local 'MapIntegrator' as parameter to non-global template
> map(functions...)

Could you please move MapIntegrator() to module-level. Then it should work.

Ali

On Tuesday, 11 December 2012 at 17:50:31 UTC, Ali Çehreli wrote:
> On 12/11/2012 08:12 AM, Zardoz wrote:
>
>
> Could you please move MapIntegrator() to module-level. Then it should work.
>
> Ali

I try it and now even with normal Map function give me errors with dmd !

public Entity MapIntegrator ( Entity me) {
  me.Integrador3Orden ();
  return me;
}

void main() {
  Entity[] objects;
...
  objects = array( map!MapIntegrator(objects) );
...
}

With this error :
dmd -w -wi -version=SReduction simulator.d entity.d vector.d -ofreduceSim
simulator.d(194): Error: template std.algorithm.map!(MapIntegrator).map does not match any function template declaration
/usr/include/dmd/phobos/std/algorithm.d(369): Error: template std.algorithm.map!(MapIntegrator).map(Range) if (isInputRange!(Unqual!(Range))) cannot deduce template function from argument types !()(Entity[])

On 12/12/2012 05:47 AM, Zardoz wrote:
> On Tuesday, 11 December 2012 at 17:50:31 UTC, Ali Çehreli wrote:
>> On 12/11/2012 08:12 AM, Zardoz wrote:
>>
>>
>> Could you please move MapIntegrator() to module-level. Then it should
>> work.
>>
>> Ali
>
> I try it and now even with normal Map function give me errors with dmd !
>
> public Entity MapIntegrator ( Entity me) {
> me.Integrador3Orden ();
> return me;
> }
>
> void main() {
> Entity[] objects;
> ...
> objects = array( map!MapIntegrator(objects) );
> ...
> }
>
> With this error :
> dmd -w -wi -version=SReduction simulator.d entity.d vector.d -ofreduceSim
> simulator.d(194): Error: template std.algorithm.map!(MapIntegrator).map
> does not match any function template declaration
> /usr/include/dmd/phobos/std/algorithm.d(369): Error: template
> std.algorithm.map!(MapIntegrator).map(Range) if
> (isInputRange!(Unqual!(Range))) cannot deduce template function from
> argument types !()(Entity[])

Strange. The following program works for me with dmd 2.060. It uses both the regular and parallel versions of map and reduce:

import std.array;
import std.algorithm;
import std.parallelism;

struct Entity
{
    void Integrador3Orden()
    {}
}

public Entity MapIntegrator ( Entity me) {
  me.Integrador3Orden ();
  return me;
}

void main() {
  Entity[] objects;

  objects = array( map!MapIntegrator(objects) );
  objects = array(taskPool.map!MapIntegrator(objects));

  int[] acelByObjs;
  int reduced = reduce!"a + b"(0, acelByObjs);
  reduced = taskPool.reduce!"a + b"(0, acelByObjs);
}

Ali