C POSIX: Analyze a Boggle board using 100% CPU on a quad core. Post: 302358513

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Top Forums Programming C POSIX: Analyze a Boggle board using 100% CPU on a quad core. Post 302358513 by HeavyJ on Friday 2nd of October 2009 07:55:28 PM

10-02-2009

Registered User

Allow me to make myself very clear:

- The lexicon data structure is immutable.
- I have named it the ADTDAWG - Adamovsky Direct Tracking Directed Acyclic Word Graph, contained in 4 arrays of basic number types.
- The character set I have chosen is 14 of the best English letters.
- There is a thread that is responsible for words that begin with each of the letters in the character set.
- The threads all call the same recursive word-discovery function, and then modify a set of global time-stamps to eliminate the duplicate word problem.
- They will never try to modify the same time-stamp because they are responsible for a different subset of the lexicon.

- I used mutexes, and condition variables to communicate when work on the current board should begin, and when it has finished.

- My question is this - Do POSIX multi-threads really allow for an optimal implementation of a micro-parallel algorithm? Or am I doing something wrong, because I am only using 45% of the power of my Quad-Core, when I should be maxing it out?

Do you really want to look at the code that I wrote? At this point, I have every reason to believe that it will introduce mass confusion. It is well written, but it requires an in-depth knowledge of lexicon data structure optimization.

So you suggest that each core has a private cache? I would love to see a block diagram of how the Core2 layout works, so that I could stop spinning my wheels on this problem.

A single thread can score 1277 of the best 23 boards found to date, each with a score around 10769 points for the TWL06 lexicon.

That means that the recursive function is being called many, many, many times per second. Should this fact be a concern?

HeavyJ

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pthread_mutex_unlock

pthread_mutex_unlock(3T)												  pthread_mutex_unlock(3T)

NAME

       pthread_mutex_unlock() - unlock a mutex.

SYNOPSIS

PARAMETERS

	      mutex	Pointer to the mutex to be unlocked.

DESCRIPTION

       The  function  is  called  by  the owner of the mutex referenced by mutex to unlock the mutex.  The manner in that the mutex is released is
       dependent upon the mutex's type attribute.  For normal and default mutexes, undefined behavior will result if  is  called  on  an  unlocked
       mutex  or  by  a  thread  that is not the current owner.  For recursive and error-checking mutexes, an error is returned if is called on an
       unlocked mutex or by a thread which is not the current owner.

       For recursive mutexes, the owner must call as many times as the mutex was locked before another thread can lock the mutex.

       If there are threads blocked on the mutex referenced by mutex when releases the mutex, the scheduling policy is	used  to  determine  which
       thread will acquire the mutex next.

RETURN VALUE

       Upon successful completion, returns zero. Otherwise, an error number is returned to indicate the error (the variable is not set).

ERRORS

       For each of the following conditions, if the condition is detected, the function returns the corresponding error number:

	      [EINVAL]	     mutex is not an initialized mutex.

	      [EPERM]	     The calling thread does not own mutex.  On HP-UX, this error is not detected for or mutexes.

	      [EFAULT]	     mutex parameter points to an illegal address.

AUTHOR

       was derived from the IEEE POSIX P1003.1c standard and HP extensions.

SEE ALSO

       pthread_mutex_init(3T), pthread_mutex_destroy(3T), pthread_mutex_lock(3T), pthread_mutex_trylock(3T).

STANDARDS CONFORMANCE

								  Pthread Library					  pthread_mutex_unlock(3T)