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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
Old 10-02-2009
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?
 

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hostinfo(8)						    BSD System Manager's Manual 					       hostinfo(8)

NAME
hostinfo -- host information SYNOPSIS
hostinfo DESCRIPTION
The hostinfo command displays information about the host system on which the command is executing. The output includes a kernel version description, processor configuration data, available physical memory, and various scheduling statistics. OPTIONS
There are no options. DISPLAY
Mach kernel version: The version string compiled into the kernel executing on the host system. Processor Configuration: The maximum possible processors for which the kernel is configured, followed by the number of physical and logical processors avail- able. Note: on Intel architectures, physical processors are referred to as cores, and logical processors are referred to as hardware threads; there may be multiple logical processors per core and multiple cores per processor package. This command does not report the number of processor packages. Processor type: The host's processor type and subtype. Processor active: A list of active processors on the host system. Active processors are members of a processor set and are ready to dispatch threads. On a single processor system, the active processor, is processor 0. Primary memory available: The amount of physical memory that is configured for use on the host system. Default processor set: Displays the number of tasks currently assigned to the host processor set, the number of threads currently assigned to the host proces- sor set, and the number of processors included in the host processor set. Load average: Measures the average number of threads in the run queue. Mach factor: A variant of the load average which measures the processing resources available to a new thread. Mach factor is based on the number of CPUs divided by (1 + the number of runnablethreads) or the number of CPUs minus the number of runnable threads when the number of runnable threads is less than the number of CPUs. The closer the Mach factor value is to zero, the higher the load. On an idle system with a fixed number of active processors, the mach factor will be equal to the number of CPUs. SEE ALSO
sysctl(8) Mac OS X October 30, 2003 Mac OS X
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