On 2017-03-30 11:29, Jon Foster wrote:
On 03/29/2017 01:15 PM, Michael Van Canneyt wrote:
On Wed, 29 Mar 2017, Dimitrios Chr. Ioannidis via fpc-pascal wrote:
Hi,
On 29/3/2017 9:57 μμ, fredvs wrote:
Hello.
Some developers treat me as dinosaur because I use threads in place
of
doing
parallelism.
Huh, ok, but why parallelism is better and how to do it with fpc ?
a nice article I've found long ago when I was researching the same
topic "Threading/Concurrency vs. Parallelism" is the following :
http://tutorials.jenkov.com/java-concurrency/concurrency-vs-parallelism.html
and I tried the multithreadprocslaz package in Lazarus :
http://wiki.freepascal.org/Parallel_procedures
Showing nicely that parallelism in a single process implies threads.
I would not pay too much attention to what these developers are
saying.
Either I'm dense, which is entirely possible, or the author of that
article didn't do a good job of making his point, even assuming he had
one.
Thinking about this a bit more I would say that "threads" are a means
(vehicle) to achieve parallelism. I think that in the majority of
programming contexts they are synonymous. But I can think of other
contexts where they may not be: Say animating a film. You have 1000
computers generating frames to be assembled into a final sequence. The
process of dispatching each frame render is most likely not going to
be done with the OSes thread call, but through a networked work queue
of some sort (ala Torque or something). So you have the "task"
(rendering the movie) being worked on in "parallel" via a networked
job dispatch mechanism.
Or modify the film format...
Example: create a 10 hour video that is composed of 100 files.
You have 100 computers, or 100 threads, or, 100 processes..Each computer
creates 1 file.
The video is composed of 100 files but is really just a single video.
You open up VLC to play the video, and it opens 100 files, but the end
user just opens a single file that links to each of these 100 files.
This could be the stupidest ridiculous parallel video creation technique
ever. I'm not sure...
Or it could be an idea...
Or the case of using "make -j ..." which "forks" multiple jobs
(compile, link, ...) in parallel based on a dependency tree.
I say threading is parallelism, even if just one form of it. The other
methods of parallelism I mentioned here could also be done in FPC with
the appropriate code.
What about the difference between parallelism vs concurrency?
Rob Pike has some videos on it and meetup events discussing it on
youtube.
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