[Issue 8774] 2.059 worked 2.060 does not: Unable to join thread

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=8774


Dmitry Olshansky <dmitry.olsh at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |dmitry.olsh at gmail.com


--- Comment #9 from Dmitry Olshansky <dmitry.olsh at gmail.com> 2012-12-23 01:58:21 PST ---
This one was actually simple to decipher - map recomputes values across
multiple iterations. I instrumented the code to show
a) ref address of threads in start loop and join loop
b) print Mapped each time a functor that creates the thread is run.

I get 2 times and 2 different addresses. The only question left is why it ever
worked.

The right aproach would be to call array on result of task map and do not
attempt 2nd lazy evluation of it.

Modifed source below:


import std.algorithm ;
import std.datetime ;
import std.range ;
import std.stdio;

import core.thread ;

import output_d ;

shared double sum ;
shared Object sumMutex ;

void partialSum ( immutable int id , immutable int sliceSize , immutable double
delta ) {
  immutable start = 1 + id * sliceSize ;
  immutable end = ( id + 1 ) * sliceSize ;
  auto localSum = 0.0 ;
  foreach ( i ; start .. end + 1 ) {
    immutable x = ( i - 0.5 ) * delta ;
    localSum += 1.0 / ( 1.0 + x * x ) ;
  }
  synchronized ( sumMutex ) { sum += localSum ; }
}

void execute ( immutable int numberOfThreads ) {
  immutable n = 1000000000 ;
  immutable delta = 1.0 / n ;
  StopWatch stopWatch ;
  stopWatch.start ( ) ;
  immutable sliceSize = n / numberOfThreads ;
  sum = 0.0 ;
  auto threads = map ! ( ( int i ) {
      auto closedPartialSum ( ) {
        immutable ii = i ;
        return delegate ( ) { partialSum ( ii , sliceSize , delta ) ; } ;
      }
      writeln("Mapped!");
      return new Thread ( closedPartialSum ) ;
      } ) ( iota ( numberOfThreads ) ) ;
  foreach ( thread ; threads ) { 
    writefln("%x", cast(void*)thread);
    thread.start ( ) ; 
  }
  foreach ( thread ; threads ) { 
    writefln("%x", cast(void*)thread);
    thread.join ( ) ; 
  }
  immutable pi = 4.0 * delta * sum ;
  stopWatch.stop ( ) ;
  immutable elapseTime = stopWatch.peek ( ).hnsecs * 100e-9 ;
  output ( __FILE__ , pi , n , elapseTime , numberOfThreads ) ;
}

int main ( immutable string[] args ) {
  sumMutex = new shared ( Object ) ;
  execute ( 1 ) ;
  execute ( 2 ) ;
  execute ( 8 ) ;
  execute ( 32 ) ;
  return 0 ;
}

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