Steve Williams wrote:
Florian Klaempfl wrote:
I'am currently thinking about implementing OpenMP support in FPC.
However, there is currently (to my knowledge) no pascal syntax defined
for OpenMp support. Do you think we can find a common syntax to simplify
things for users? I've some ideas how it be done, but I want to hear
other ideas first so they are maybe better if they aren't influenced by
my ideas :)
I started also a wiki page about it
http://www.freepascal.org/wiki/index.php/OpenMP_support where ideas can
be written down and shared.
I would suggest something along the lines of the C/C++ implementation,
but using the Pascal form of compiler directives.
Using some of the documented examples in the v2.5 spec:
Example A.1.1:
procedure a1(n: Integer; a: PSingleArray; b: PSingleArray);
var
i: Integer;
begin
{$omp parallel for}
for i := 1 to n - 1 do
b^[i] := (a^[i] + a^[i - 1]) / 2.0;
end;
Brrr.... using local defines look not native to the language.
Why not something like as (refered in another thread) pascal-fc which
uses cobegin..coend or known blocks like asm..end; try..end;
for instance:
omp..end;
parralel..end;
so:
procedure a1(n: Integer; a: PSingleArray; b: PSingleArray);
var
i: Integer;
begin
for i := 1 to n - 1 do
parallel
b^[i] := (a^[i] + a^[i - 1]) / 2.0;
end;
end;
Example A.5.1:
uses omp;
begin
omp_set_dynamic(1);
{$omp parallel num_threads(10)}
begin
(* Do work here *)
end;
end;
uses omp;
begin
omp_set_dynamic(1);
// {$omp parallel num_threads(10)}
// why not:
omp_set_num_threads(10);
parallel
(* Do work here *)
end;
end;
Example A.13.1:
interface
function dequeue(var a: Single): Integer;
procedure work(i: Integer; var a: Single);
implementation
procedure a13(var x: Single; var y: Single);
var
ix_next, iy_next: Integer;
begin
{$omp parallel shared(x, y) private(ix_next, iy_next)}
begin
{$omp critical (xaxis)}
ix_next := dequeue(x);
work(ix_next, x);
{$omp critical (yaxis)}
iy_next := dequeue(y);
work(iy_next, y);
end;
end;
procedure a13(var ax: Single; var ay: Single);
begin
parallel
shared
x: Single; absolute ax;
y: Single; absolute ay;
private
ix_next, iy_next: Integer;
begin
// where does xaxis come from ?
// {$omp critical (xaxis)}
ix_next := dequeue(x);
work(ix_next, x);
// where does yaxis come from ?
// {$omp critical (yaxis)}
iy_next := dequeue(y);
work(iy_next, y);
end;
end;
or:
procedure a13(var ax: Single; shared var y: Single);
shared var
x: Single; absolute ax;
// y: Single; absolute ay;
private var
ix_next, iy_next: Integer;
begin
parallel
// where does xaxis come from ?
// {$omp critical (xaxis)}
ix_next := dequeue(x);
work(ix_next, x);
// where does yaxis come from ?
// {$omp critical (yaxis)}
iy_next := dequeue(y);
work(iy_next, y);
end;
end;
Marc
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