I found a nice finite difference scheme, where the solving part can be parallelized on 2 processors at each time-step.
I was a bit surprised to notice that the parallelized algorithm ran in some cases twice slower than the same algorithm not parallelized. I tried ForkJoinPool, ThreadPoolExecutor, my one notify/wait based parallelization. All resulted in similar performance compared to just calling thread1.run() and thread2.run() directly.
I am still a bit puzzled by the results. Increasing the time of the task by increasing the number of discretization points does not really improve the parallelization. The task is relatively fast to perform and is repeated many (around of 1000) times, so synchronized around 1000 times, which is likely why parallelization is not great on it: synchronization overhead reaps any benefit of the parallelization. But I expected better. Using a Thread pool of 1 thread is also much slower than calling run() twice (and fortunately slower than the pool of 2 threads).
Wednesday, February 13, 2013
Parallel Can Be Slower
I found a nice finite difference scheme, where the solving part can be parallelized on 2 processors at each time-step.
I was a bit surprised to notice that the parallelized algorithm ran in some cases twice slower than the same algorithm not parallelized. I tried ForkJoinPool, ThreadPoolExecutor, my one notify/wait based parallelization. All resulted in similar performance compared to just calling thread1.run() and thread2.run() directly.
I am still a bit puzzled by the results. Increasing the time of the task by increasing the number of discretization points does not really improve the parallelization. The task is relatively fast to perform and is repeated many (around of 1000) times, so synchronized around 1000 times, which is likely why parallelization is not great on it: synchronization overhead reaps any benefit of the parallelization. But I expected better. Using a Thread pool of 1 thread is also much slower than calling run() twice (and fortunately slower than the pool of 2 threads).
I was a bit surprised to notice that the parallelized algorithm ran in some cases twice slower than the same algorithm not parallelized. I tried ForkJoinPool, ThreadPoolExecutor, my one notify/wait based parallelization. All resulted in similar performance compared to just calling thread1.run() and thread2.run() directly.
I am still a bit puzzled by the results. Increasing the time of the task by increasing the number of discretization points does not really improve the parallelization. The task is relatively fast to perform and is repeated many (around of 1000) times, so synchronized around 1000 times, which is likely why parallelization is not great on it: synchronization overhead reaps any benefit of the parallelization. But I expected better. Using a Thread pool of 1 thread is also much slower than calling run() twice (and fortunately slower than the pool of 2 threads).
Scala is Mad (part 2)
I still did not abandon Scala despite my previous post, mainly because I have already quite a bit of code, and am too lazy to port it. Furthermore the issues I detailed were not serious enough to motivate a switch. But these days I am more and more fed up with Scala, especially because of the Eclipse plugin. I tried the newer, the beta, and the older, the stable, the conclusion is the same. It's welcome but:
It's nice to type less, but if overall writing is slower because of the above issues, it does not help. Beside curiosity of a new language features, I don't see any point in Scala today, even if some of the ideas are interesting. I am sure it will be forgotten/abandoned in a couple of years. Today, if I would try a new language, I would give Google Go a try: I don't think another big language can make it/be useful on the JVM (beside a scripting kind of language, like JavaScript or Jython).
Google Go focuses on the right problem: concurrency. It also is not constrained to JVM limitation (on the other side one can not use a Java library - but open source stuff is usually not too difficult to port from one language to another). It has one of the fastest compilers. It makes interesting practical choices: no inheritance.
- code completion is not great compared to Java. For example one does not seem to be able to see the constructor parameters, or the method parameters can not be automatically populated.
- the plugin makes Eclipse *very* slow. Everything seems at least 3-5x slower. On the fly compilation is also much much slower than Java's.
It's nice to type less, but if overall writing is slower because of the above issues, it does not help. Beside curiosity of a new language features, I don't see any point in Scala today, even if some of the ideas are interesting. I am sure it will be forgotten/abandoned in a couple of years. Today, if I would try a new language, I would give Google Go a try: I don't think another big language can make it/be useful on the JVM (beside a scripting kind of language, like JavaScript or Jython).
Google Go focuses on the right problem: concurrency. It also is not constrained to JVM limitation (on the other side one can not use a Java library - but open source stuff is usually not too difficult to port from one language to another). It has one of the fastest compilers. It makes interesting practical choices: no inheritance.
Scala is Mad (part 2)
I still did not abandon Scala despite my previous post, mainly because I have already quite a bit of code, and am too lazy to port it. Furthermore the issues I detailed were not serious enough to motivate a switch. But these days I am more and more fed up with Scala, especially because of the Eclipse plugin. I tried the newer, the beta, and the older, the stable, the conclusion is the same. It's welcome but:
It's nice to type less, but if overall writing is slower because of the above issues, it does not help. Beside curiosity of a new language features, I don't see any point in Scala today, even if some of the ideas are interesting. I am sure it will be forgotten/abandoned in a couple of years. Today, if I would try a new language, I would give Google Go a try: I don't think another big language can make it/be useful on the JVM (beside a scripting kind of language, like JavaScript or Jython).
Google Go focuses on the right problem: concurrency. It also is not constrained to JVM limitation (on the other side one can not use a Java library - but open source stuff is usually not too difficult to port from one language to another). It has one of the fastest compilers. It makes interesting practical choices: no inheritance.
- code completion is not great compared to Java. For example one does not seem to be able to see the constructor parameters, or the method parameters can not be automatically populated.
- the plugin makes Eclipse *very* slow. Everything seems at least 3-5x slower. On the fly compilation is also much much slower than Java's.
It's nice to type less, but if overall writing is slower because of the above issues, it does not help. Beside curiosity of a new language features, I don't see any point in Scala today, even if some of the ideas are interesting. I am sure it will be forgotten/abandoned in a couple of years. Today, if I would try a new language, I would give Google Go a try: I don't think another big language can make it/be useful on the JVM (beside a scripting kind of language, like JavaScript or Jython).
Google Go focuses on the right problem: concurrency. It also is not constrained to JVM limitation (on the other side one can not use a Java library - but open source stuff is usually not too difficult to port from one language to another). It has one of the fastest compilers. It makes interesting practical choices: no inheritance.
Friday, February 01, 2013
From OpenSuse to Ubuntu 13.04
In my Linux quest, I changed distribution again on my home desktop, from OpenSuse 11.1 with KDE to Ubuntu 13.04 (not yet released - so alpha) with Unity. Why?
- KDE was crashing a bit too often for my taste (more than once a week). Although I enjoyed the KDE environment.
- Not easy to transfer files to my Android 4.2 phone. Ubuntu 13.04 is not fully there yet, but is on its way.
- zypper is a bit too specific for my taste. I would be ok with yum+rpm or apt-get, but another tool just for a single distribution, not really.
- Plus I'm just curious what's next for Ubuntu, and Linux makes it very simple to change distributions, and reinstall applications with the same settings. So it's never a big task to change distribution.
- I somehow like how Ubuntu feels, not sure what it is exactly, maybe the Debian roots.
When people say OpenSuse is rock solid, I don't have that impression, at least on the desktop. It might have been true in the past. But in the past, most distros were very stable. I never remember having big stability issues until, maybe, late 2010. In the early 2000s, a laptop would work very well with Linux, suspend included. I remember that my Dell Inspiron 8200 was working perfectly with Mandrake & WindowMaker. Nowadays, it never seem to work that well, but is just ok: Optimus comes to mind (especially with external screen), suspend problems, wifi (not anymore).
So far I can see that Ubuntu 13.04 is prettier than the past versions, the installer is great. I encrypted my two hard disks, it was just a matter of ticking a box - very nice. Unity Launcher, while interesting, is still not the greatest tool to find an installed application (compared to KDE launcher or Gnome Shell). I don't notice any stability issue so far, even though I have some popup messages that sometimes tells me something crashed (typical for an alpha version). If I just ignore the messages, everything seems fine. OpenSuse-KDE was logging me out (session crash), or just stopped completely being responsive (hard reset necessary).
- KDE was crashing a bit too often for my taste (more than once a week). Although I enjoyed the KDE environment.
- Not easy to transfer files to my Android 4.2 phone. Ubuntu 13.04 is not fully there yet, but is on its way.
- zypper is a bit too specific for my taste. I would be ok with yum+rpm or apt-get, but another tool just for a single distribution, not really.
- Plus I'm just curious what's next for Ubuntu, and Linux makes it very simple to change distributions, and reinstall applications with the same settings. So it's never a big task to change distribution.
- I somehow like how Ubuntu feels, not sure what it is exactly, maybe the Debian roots.
When people say OpenSuse is rock solid, I don't have that impression, at least on the desktop. It might have been true in the past. But in the past, most distros were very stable. I never remember having big stability issues until, maybe, late 2010. In the early 2000s, a laptop would work very well with Linux, suspend included. I remember that my Dell Inspiron 8200 was working perfectly with Mandrake & WindowMaker. Nowadays, it never seem to work that well, but is just ok: Optimus comes to mind (especially with external screen), suspend problems, wifi (not anymore).
So far I can see that Ubuntu 13.04 is prettier than the past versions, the installer is great. I encrypted my two hard disks, it was just a matter of ticking a box - very nice. Unity Launcher, while interesting, is still not the greatest tool to find an installed application (compared to KDE launcher or Gnome Shell). I don't notice any stability issue so far, even though I have some popup messages that sometimes tells me something crashed (typical for an alpha version). If I just ignore the messages, everything seems fine. OpenSuse-KDE was logging me out (session crash), or just stopped completely being responsive (hard reset necessary).
From OpenSuse to Ubuntu 13.04
In my Linux quest, I changed distribution again on my home desktop, from OpenSuse 11.1 with KDE to Ubuntu 13.04 (not yet released - so alpha) with Unity. Why?
- KDE was crashing a bit too often for my taste (more than once a week). Although I enjoyed the KDE environment.
- Not easy to transfer files to my Android 4.2 phone. Ubuntu 13.04 is not fully there yet, but is on its way.
- zypper is a bit too specific for my taste. I would be ok with yum+rpm or apt-get, but another tool just for a single distribution, not really.
- Plus I'm just curious what's next for Ubuntu, and Linux makes it very simple to change distributions, and reinstall applications with the same settings. So it's never a big task to change distribution.
- I somehow like how Ubuntu feels, not sure what it is exactly, maybe the Debian roots.
When people say OpenSuse is rock solid, I don't have that impression, at least on the desktop. It might have been true in the past. But in the past, most distros were very stable. I never remember having big stability issues until, maybe, late 2010. In the early 2000s, a laptop would work very well with Linux, suspend included. I remember that my Dell Inspiron 8200 was working perfectly with Mandrake & WindowMaker. Nowadays, it never seem to work that well, but is just ok: Optimus comes to mind (especially with external screen), suspend problems, wifi (not anymore).
So far I can see that Ubuntu 13.04 is prettier than the past versions, the installer is great. I encrypted my two hard disks, it was just a matter of ticking a box - very nice. Unity Launcher, while interesting, is still not the greatest tool to find an installed application (compared to KDE launcher or Gnome Shell). I don't notice any stability issue so far, even though I have some popup messages that sometimes tells me something crashed (typical for an alpha version). If I just ignore the messages, everything seems fine. OpenSuse-KDE was logging me out (session crash), or just stopped completely being responsive (hard reset necessary).
- KDE was crashing a bit too often for my taste (more than once a week). Although I enjoyed the KDE environment.
- Not easy to transfer files to my Android 4.2 phone. Ubuntu 13.04 is not fully there yet, but is on its way.
- zypper is a bit too specific for my taste. I would be ok with yum+rpm or apt-get, but another tool just for a single distribution, not really.
- Plus I'm just curious what's next for Ubuntu, and Linux makes it very simple to change distributions, and reinstall applications with the same settings. So it's never a big task to change distribution.
- I somehow like how Ubuntu feels, not sure what it is exactly, maybe the Debian roots.
When people say OpenSuse is rock solid, I don't have that impression, at least on the desktop. It might have been true in the past. But in the past, most distros were very stable. I never remember having big stability issues until, maybe, late 2010. In the early 2000s, a laptop would work very well with Linux, suspend included. I remember that my Dell Inspiron 8200 was working perfectly with Mandrake & WindowMaker. Nowadays, it never seem to work that well, but is just ok: Optimus comes to mind (especially with external screen), suspend problems, wifi (not anymore).
So far I can see that Ubuntu 13.04 is prettier than the past versions, the installer is great. I encrypted my two hard disks, it was just a matter of ticking a box - very nice. Unity Launcher, while interesting, is still not the greatest tool to find an installed application (compared to KDE launcher or Gnome Shell). I don't notice any stability issue so far, even though I have some popup messages that sometimes tells me something crashed (typical for an alpha version). If I just ignore the messages, everything seems fine. OpenSuse-KDE was logging me out (session crash), or just stopped completely being responsive (hard reset necessary).
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