Re: Gnat 3.15p & Windows & Hyperthreading Q

[Marin David Condic <nobody@noplace.com>]

On a quick scan, I don't see anything obvious. Let me take a look at it 
and I'll see if I spot anything that might be problematic.

MDC

tmoran@acm.org wrote:
> 
>     The original program was posted under "Ada bench : count words",
> as was the dual-Celeron timing.  The hyperthreading timing was a personal
> communication.  It's possible the person was mistaken in thinking they
> had hyperthreading turned on, with processor affinities set correctly.
> I'm inquiring further.
> 
>   So here's the benchmark.  It reads a text file from Standard Input,
> preferably at least a megabyte to get a decent timing read, and prints
> line, word, and character counts to Standard Output.  The number of
> CPU-heavy tasks is the number of elements of
>   Counter : array(1 .. 2) of Counters;
> Probably increasing the buffer size, by lessening task interactions,
> would speed it up and improve the multi-tasking benefit.
> 
> with Ada.Calendar,
>      Ada.Streams,
>      Ada.Streams.Stream_IO,
>      Ada.Text_IO,
>      Ada.Text_IO.Text_Streams;
> procedure Cwt is
>   use Ada.Streams;
>   use type Ada.Calendar.Time;
> 
>   T0  : Ada.Calendar.Time := Ada.Calendar.Clock;  -- start timing
>   T1  : Ada.Calendar.Time;
> 
>   subtype Buffer_Type is Stream_Element_Array(1 .. 4096);
> 
>   LF      : constant Stream_Element := Character'pos(Ascii.LF);
>   Is_Whitespace : constant array(Stream_Element) of Boolean
>     := (Character'pos(Ascii.LF) | Character'pos(Ascii.HT)
>         | Character'pos(' ') => True, others => False);
> 
>   -- "Counters" tasks run independently, asking Data_Source for buffer loads
>   -- and tallying word and line counts.  When done, they wait for their
>   -- (partial) counts to be harvested, then terminate.
> 
>   task type Counters is
>     entry Harvest(Line_Count, Word_Count : out Natural);
>   end Counters;
> 
>   -- Data_Source is the IO task, supplying data as requested to Counters.
>   -- Note that Data_Source counts the whitespace->non-white transitions
>   -- at the ends of buffers.  Counters' partial counts are added to that.
>   -- Data_Source also counts the Total number of characters.
> 
>   task Data_Source is
>     entry Get(Buffer : out Buffer_Type;
>               Last : out Stream_Element_Offset);
>   end Data_Source;
> 
>   task body Counters is
>     Buffer : Buffer_Type;
>     Last : Stream_Element_Offset;
>     Lines, Words, Total : Natural := 0;
>     In_Whitespace : Boolean;
>   begin
>     loop
>       Data_Source.Get(Buffer, Last);
>       exit when Last = 0;
>       In_Whitespace := Is_Whitespace(Buffer(1));
>       for I in 1 .. Last loop
>         if Is_Whitespace(Buffer(I)) then
>           if Buffer(I) = LF then
>             Lines := Lines + 1;
>           end if;
>           In_Whitespace := True;
>         elsif In_Whitespace then
>           In_Whitespace := False;
>           Words := Words + 1;
>         end if;
>       end loop;
>       exit when Last < Buffer'last;
>     end loop;
>     accept Harvest(Line_Count, Word_Count : out Natural) do
>       Line_Count := Lines;
>       Word_Count := Words;
>     end;
>   end Counters;
> 
>   Lines, Words, Total : Natural := 0;
> 
>   task body Data_Source is
>     Stream  : Ada.Text_IO.Text_Streams.Stream_Access;
>     At_End : Boolean := False;
>     In_Whitespace : Boolean := True; -- we must count at edges of buffer loads
>   begin
>     Stream := Ada.Text_IO.Text_Streams.Stream(Ada.Text_IO.Current_Input);
>     loop
>       select
>         accept Get(Buffer : out Buffer_Type;
>                    Last : out Stream_Element_Offset) do
>           if At_End then Last := 0;
>           else
>             Ada.Streams.Read(Ada.Streams.Root_Stream_Type'Class(Stream.all),
>                              Buffer, Last);
>             Total := Total+Integer(Last);
>             if Last > 0 then
>               if In_Whitespace and not Is_Whitespace(Buffer(1)) then
>                 Words := Words+1;
>               end if;
>               In_Whitespace := Is_Whitespace(Buffer(Last));
>             end if;
>             if Last < Buffer'last then At_End := True;end if;
>           end if;
>         end;
>       or terminate;
>       end select;
>     end loop;
>   end Data_Source;
> 
>   A_Line_Count, A_Word_Count : Natural := 0;
> 
>   Counter : array(1 .. 2) of Counters;
> 
> begin
> 
>   for i in Counter'range loop
>     Counter(i).Harvest(A_Line_Count, A_Word_Count);
>     Lines := Lines+A_Line_Count;
>     Words := Words+A_Word_Count;
>   end loop;
> 
>   T1 := Ada.Calendar.Clock;
> 
>   Ada.Text_IO.Put_Line(Natural'Image(Lines)
>                        & Natural'Image(Words)
>                        & Natural'Image(Total));
>   Ada.Text_IO.Put_Line("took" & Duration'Image(T1 - T0));
> end Cwt;

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Marin David Condic
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