Re: Simple parallel foreach and summation/reduction

[Chris Katko via Digitalmars-d-learn]

On Saturday, 22 September 2018 at 02:26:41 UTC, Chris Katko wrote:
On Saturday, 22 September 2018 at 02:13:58 UTC, Chris Katko 
wrote:
On Friday, 21 September 2018 at 12:15:59 UTC, Ali Çehreli 
wrote:

On 09/21/2018 12:25 AM, Chris Katko wrote:

[...]


You can use a free-standing function as a workaround, which 
is included in the following chapter that explains most of 
std.parallelism:


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

That chapter is missing e.g. the newly-added fold():

  https://dlang.org/phobos/std_parallelism.html#.TaskPool.fold

Ali


Okay... so I've got it running. The problem is, it uses tons 
of RAM. In fact, proportional to the working set.


T test(T)(T x, T y)
{
return x + y;
}

double monte(T)(T x)
{
double v = uniform(-1F, 1F);
double u = uniform(-1F, 1F);
if(sqrt(v*v + u*u) < 1.0)
{
return 1;
}else{
return 0;
}
}

auto taskpool = new TaskPool();
sum = taskpool.reduce!(test)(
taskpool.amap!monte(
iota(num)
)   );  
taskpool.finish(true);

100 becomes ~8MB
1000 becomes 80MB
1, I can't even run because it says "Exception: Memory 
Allocation failed"


Also, when I don't call .finish(true) at the end, it just sits 
there forever (after running) like one of the threads won't 
terminate. Requiring a control-C. But the docs and examples 
don't seem to indicate I should need that...


So I looked into it. It's amap that explodes in RAM.

Per the docs, amap has "less overhead but more memory usage." 
While map has more overhead but less memory usage and "avoids the 
need to keep all results in memory."


But, if I make a call to map... it doesn't compile! I get:

Error: no [] operator overload for type 
std.parallelism.TaskPool.map!(monte).map!(Result).map.Map


Simply changing amap to map here:

sum = taskPool.reduce!(test)
(
taskPool.map!(monte)(range)
);

Re: SerialPort

[dangbinghoo via Digitalmars-d-learn]

On Thursday, 20 September 2018 at 10:51:52 UTC, braboar wrote:
I am going to play with serial port read/write, so I fetched 
serial-port. After that, I wrote simple program:


auto port_name = "/dev/ttyUSB1";
auto reader = new SerialPort(port_name);
reader.dataBits(DataBits.data8);
reader.stopBits(StopBits.one);
reader.parity(Parity.none);
reader.speed(BaudRate.BR_230400);
string[] income;
reader.read(income);

and the result is

serial.device.TimeoutException


Can anybody give me a guide of using serial port?

And one more question: how to outline code blocks? ''' or --- 
can't help me.


here is my code really works:

com is `reader` object in your code.

```
void writeBytes(ubyte[] arr)
{
com.write(arr);
}

void serialThread()
{
ubyte[500] buff;

running = true;
while (running)
{
string str;
size_t readed;

try
{
readed = com.read(buff);
// if (readed > 0) {
//writeln("com port readed " ~ 
std.conv.to!string(readed));

str = cast(string)(buff[0 .. readed]).idup;
// Don't use writeln for console or string serail 
application.

write(str);
// }
}
// must catch for continous reading, otherwize, com 
port will block.

catch (TimeoutException e)
{
}
   }
}
```

thanks!