Thanks everyone for the replies.
I wasn't sure how std.parallel operated but I thought it would
launch at most a number of threads equal to the number of cores
on the machine, just as Ali confirmed and similar to what
Windows' thread pool does.
On Sunday, 5 October 2014 at 21:53:23 UTC, Ali Çehreli wrote:
On 10/05/2014 02:40 PM, Sativa wrote:
> foreach(i; thds) { ulong s = 0; for(ulong k = 0; k <
> iter/numThreads; k++)
The for loop condition is executed at every iteration and
division is an expensive operation. Apparently, the
On 10/05/2014 02:40 PM, Sativa wrote:
> foreach(i; thds) { ulong s = 0; for(ulong k = 0; k <
> iter/numThreads; k++)
The for loop condition is executed at every iteration and division is an
expensive operation. Apparently, the compiled does some optimization
when the divisor is known at c
On Sunday, 5 October 2014 at 21:25:39 UTC, Ali Çehreli wrote:
import std.stdio, std.cstream, std.parallelism, std.datetime,
std.range, core.atomic;
void main()
{
StopWatch sw;
shared ulong sum1 = 0; ulong sum2 = 0, sum3 = 0, time1, time2,
time3;
enum numThreads = 4; // If nu
On 10/05/2014 07:27 AM, flamencofantasy wrote:
> I am summing up the first 1 billion integers in parallel and in a single
> thread and I'm observing some curious results;
>
> parallel sum : 45, elapsed 102833 ms
> single thread sum : 45, elapsed 1667 ms
>
> The par
Two problems, one, you should create your threads outside the
stop watch, it is not generally a fair comparison in the real
world. It throws of the results for short tasks.
Second, you are creating one thread per integer, this is bad. Do
you really want to create 1B threads when you only have
Welcome to the world of multithreading.
You have just discovered that atomic operations are performance
killers, congratulations on this.
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On 05/10/14 15:27, flamencofantasy via Digitalmars-d-learn wrote:
> Hello,
>
> I am summing up the first 1 billion integers in parallel and in a
> single thread and I'm observing some curious results;
I am fairly certain that your use of "parallel fo
Hello,
I am summing up the first 1 billion integers in parallel and in a
single thread and I'm observing some curious results;
parallel sum : 45, elapsed 102833 ms
single thread sum : 45, elapsed 1667 ms
The parallel version is 60+ times slower on my i7-3770K C
