Posts by Jesse Viviano
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1) Message boards : Science : Differences between two applications (Message 11472)
Posted 2529 days ago by Jesse Viviano
I did not know that. I thought that I was being given the non-SSE application. I guess that this means that my initial guess as why I am going into EDF mode is ruled out. I am now noticing that the deadlines set on the regular application are probably too low, or they were set with non hyper-threading processors in mind like the Core 2 series. Hyper-threading improves work unit throughput, but lengthens the compute time of each one individually.

By the way, has anyone tried to write a true 64-bit application to see if it offers any significant performance benefits on various processors? Because both the SSE unit and the integer unit in 64-bit mode can now operate with 64-bit integers instead of only the SSE unit which is the only unit that could handle 64-bit math directly in 32-bit mode, could this lead to more speed due to having the integer unit and the SSE unit working in parallel? The numbers shown at http://boinc.thesonntags.com/collatz/highest_steps.php certainly exceed the 64-bit width of a 64-bit processor's integer unit, but the same limitation applies to SSE, which cannot handle 128-bit integers directly. However, the 64-bit register is only exceeded once with such numbers, while these numbers would exceed a 32-bit register many times over making the SSE unit the only viable location to handle such numbers in 32-bit x86, and that 64-bit x86 would handle these numbers with a small amount of difficulty.
2) Message boards : Number crunching : Keep mini collatz CPU app and drop collatz CPU app? (Message 11451)
Posted 2530 days ago by Jesse Viviano
I noticed something wrong of which I wrote about in this thread. The server is sending the non-SSE collatz application to 64-bit clients. Since AMD included and extended SSE2 (of which SSE is a subset of) when defining AMD64, the server has no business sending the non-SSE application to 64-bit clients whatsoever if it was working correctly and if there is an SSE application. I also noticed that the SSE-optimized mini-collatz application was sent to me. The regular collatz application is sending me into EDF-mode, but the SSE-optimized mini-collatz application is completing its work on time. Could the long regular collatz crunch times be attributed to sending a suboptimal application? Fixing this might cut down on crunch time.

Another suggestion would be to refuse to send collatz work to non-SSE enabled clients. If my Core i7 980X is having trouble with these work units using the non-SSE application, I doubt that a Pentium II or an Athlon would have the speed to handle a regular collatz work unit. An Athlon without SSE probably would require 3DNow! Professional optimization to possibly handle a regular collatz work unit.
3) Message boards : Science : Differences between two applications (Message 11450)
Posted 2530 days ago by Jesse Viviano
The reason I am interested is that I am running into EDF mode on the non-SSE regular collatz work units. If SSE was used like in the mini-collatz application, I think that I would not get into this situation.
4) Message boards : Science : Differences between two applications (Message 11449)
Posted 2530 days ago by Jesse Viviano
I just noticed that the "64-bit" applications are just rereleased 32-bit applications by looking in the task manager and noticing the *32 next to its process name. Since SSE is guaranteed to be in 64-bit x86 processors because it was included as part of AMD's definition of AMD64 which Intel then mostly copied, why isn't the SSE application sent for regular collatz CPU work units to 64-bit clients and only is sent for mini-collatz CPU work units?
5) Message boards : Science : Differences between two applications (Message 11421)
Posted 2532 days ago by Jesse Viviano
I noticed these two collatz applications which are giving me questions:

  • Microsoft Windows running on an AMD x86_64 or Intel EM64T CPU version 2.00 which was installed into this project on 13 Sep 2009 16:01:09 UTC
  • Microsoft Windows running on an AMD x86_64 or Intel EM64T CPU version 2.00 (sse) which was installed into this project on 13 Sep 2009 16:01:09 UTC


If you know anything about the AMD64 (aka x86-64, EM64T, and Intel 64) architecture, you would know that SSE2 (which includes SSE) is guaranteed to be present because AMD made SSE2 into the standard FPU for AMD64, extended SSE2 to 16 registers, and deprecated the x87 FPU in 64-bit mode, so OS support for saving the x87 FPU's contents is not guaranteed for 64-bit applications.

Therefore, my questions are as follows: What are the differences between the two, and why do we need both of them? I would think that you could have just one of them and get rid of the slower one. The same thing could be asked about the mini-collatz applications.





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