Why is JVM faster than CLR?

hi
i wrote a N-body algorithm in both Java and C# (shown below). i executed it using .NET CLR and JDK1.4.1. in JDK it is twice as fast as .NET (on win2000). now i am trying to find out why is it so??
the interesting thing is that i ran some other algorithms like FFT and graph alogrithms, and they are faster in .NET. so i want to find is there some operation in the below algorithm that is making it run faster in JDK.
in general, what can the possible reasons be for JVM to run faster than CLR?
thanks
double G = 6.6726E-11;
double difference = 0.0;
for(int i=0; i<numBodies; i++)
     accelarations[i] = 0.0;
     for(int j=0; j<numBodies; j++)
          if(i != j)
          difference = radii[i] - radii[j];
          if(difference != 0)
          accelarations[i] += masses/(Math.pow(difference, 2));
     accelarations[i] *= G;

Interesting N-Body problem that treats accelerations as scalars.
Anyway, if there is no optimisation for small integer powers in the Math.pow() method, then I'd expect almost all the time is used there or in its equivalent in .NET. Hardly a meaningful test of relative performance.
Try using (difference * difference) instead.
Sylvia.

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Wipe the drive on the new system and Reinstall OS X. Factory installs aren't all they are supposed to be. Sometimes corrupted from the Get Go.
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Why would oracle 9i drivers faster than oracle 10g drivers against a 10g?

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steffi2 wrote:
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Why is kernel-2.6.9 (OEL-4) faster than kernel-2.6.18 (OEL-5) ?

Hi,
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Is there anybody in this forum who experienced the same, say running OEL-4 before migrating to OEL-5?
Here are two examples showing different execution times on OEL-4.5 (kernel-2.6.9-55.0.5.0.1.EL.i686, gcc-3.4.6-8.0.1) and OEL-5 (kernel-2.6.18-8.1.10.0.1.el5, gcc-4.1.1-52.el5.2). The first example is trivial but very sensitive to overal system load and kernel version. The second example is "Sieve of Eratosthenes" - the program for finding prime numbers (CPU bound).
EXAMPLE 1.
/* Simle program for text screen console */
/* very sensitive to overall system load */
/* and kernel version                     */
#include <stdio.h>
int main(void)
    register int i;
    for(i = 0; i < 1000000; i++)
     printf(" %d ", i);
    return 0;
/* end of program */
$ gcc -O2 -o example1 -s example1.c
$ time ./example1The average execution times on OEL-4.5 and OEL-5 are as follow:
Mode      OEL-4.5         OEL-5
real      0m3.141s        0m4.931s
user      0m0.394s        0m0.366s
sys       0m2.747s        0m4.563s
----------------------------------As we can see, the program on the same machine, compiled and run on OEL-4.5 (gcc-3.4.6 and kernel-2.6.9) is 57% faster than the same program compiled and run on OEL-5 (gcc-4.1.1 and kernel-2.6.18), although gcc-4.1.1 produces much faster binary code. Since the times the process spent in user mode are almost equal on both OS, the whole difference is due to the time the process spent in kernel mode. Note that kernel mode (sys) is taking 66% more time on OEL-5. It tells me that "something" in the kernel-2.6.18 slows down the execution of the program.
In the second example OEL-4.5 is also faster than OEL-5, but the differences in execution times are not so drastic as in the first example.
EXAMPLE 2.
/*           Sieve of Eratosthenes           */
#define GNUSOURCE
#include <stdio.h>
#include <stdlib.h>
#define MAX_PRIME_AREA 100000
#define REPEAT_LOOP 10000
int main(void)
    int prime, composite, count;
    char *sieve_array;
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     fprintf(stderr,"Memory block too big!\nMemory allocation failed!\a\n");
     exit(EXIT_FAILURE);
    for(count = 0; count < REPEAT_LOOP; count++)
     for(prime = 0; prime < (MAX_PRIME_AREA + 1); prime++)
             *(sieve_array + prime) = (char) '\0';
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             for(composite = (2 * prime); composite < (MAX_PRIME_AREA + 1); composite += prime)
              *(sieve_array + composite) = (char) 'X'; /* offset composite is a composite */
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        for(prime = 3; prime < (MAX_PRIME_AREA + 1); prime += 2)
            if ( *(sieve_array + prime) == 'P' )
                fprintf(stdout, "%d\n", prime);
    free(sieve_array);
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/* End of Sieve of Eratosthenes */The average execution times on the same machine on OEL-4.5 and OEL-5 are:
MAX_PRIME_AREA     Mode         OEL-4.5         OEL-5
                   real         0m9.196s        0m10.531s
   100000          user         0m9.189s        0m10.478s
                   sys          0m0.002s        0m0.010s
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   200000          user         0m20.233s       0m21.490s
                   sys          0m0.020s        0m0.025s
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   300000          user         0m30.684s       0m33.456s
                   sys          0m0.024s        0m0.032s
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   400000          user         1m10.087s       1m14.704s
                   sys          0m0.075s        0m0.079s
---------------------------------------------------------Does this ring a bell with anyone? Any clue why?
N.J.

An hour? Hard to believe or is your hardware that
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Oracle doesn't ship
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What's your time to build a single kernel (which
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cat /proc/cpuinfo | grep "model name"
model name      : AMD Athlon(tm) 64 Processor 3700+with about 2GB of RAM
free -m
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Mem:          2024       1957         67          0        368       1291
-/+ buffers/cache:        297       1727
Swap:         3827         24       3803under
uname -a
Linux base 2.6.22-gentoo-r5 #5 PREEMPT Mon Sep 10 22:32:37 CEST 2007 i686 AMD Athlon(tm) 64 Processor 3700+ AuthenticAMD GNU/LinuxThis is what i did
cd /usr/src/linux
make clean
time nice -n 19 genkernel --lvm2 --makeopts="-j2" --oldconfig all
* Running with options: --lvm2 --makeopts=-j2 --oldconfig all
* Linux Kernel 2.6.22-gentoo-r5 for x86...*
mount: /boot mounted successfully!
* config: >> Running oldconfig...
* config: --no-clean is enabled; leaving the .config alone.
*         >> Compiling 2.6.22-gentoo-r5 bzImage...
*         >> Compiling 2.6.22-gentoo-r5 modules......
real    17m30.582s
user    16m8.480s
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C.

CTAS is over x10 faster than it's select statement, why?

Hi gurus -
Oracle 11gR2
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No it's not guessing game. Here is my query with elapsed time,
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OT_PAY_RATE,
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Why is Firefox Developer more stable and faster than regular Firefox?

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Ubuntu is booting up faster than Arch on my computer why would that be

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Vector is way faster than HashMap (why?)

I thought that HashMap would be faster than Vector (in adding stuff) ... could anyone explain to me why there was such a HUGE difference??
here's the code I used:
public class SpeedTest
public static void main(String[] args)
   final int max=1000001;
   Integer[] arrayzinho = new Integer[max];
   Arrays.fill(arrayzinho,0,max,new Integer(1));
   Vector jota = new Vector(max,max);
   HashMap ele = new HashMap(max,1);
   System.out.println("Adicionando " + (max-1) + " elementos ao array...");
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//ops
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//ops
System.out.println("Adicionando " + (max-1) + " elementos ao HashMap...");
tempo = System.currentTimeMillis();
for(int i=0;i<max;i++)
ele.put(arrayzinho[i],arrayzinho[i]);
System.out.println("A opera??o demorou " + ((System.currentTimeMillis()-tempo)) + " msecs.");
Of course, when adding to HashMap, two values are entered instead of just the one added in the Vector... But, even doubling the time Vector used, the difference is huge!
here's some output I've got:
1:
Adicionando 1000000 elementos ao array...
A opera??o demorou 4500 msecs.
Adicionando 1000000 elementos ao Vector...
A opera??o demorou 469 msecs.
Adicionando 1000000 elementos ao HashMap...
A opera??o demorou 7906 msecs.
2:
Adicionando 1000000 elementos ao array...
A opera??o demorou 4485 msecs.
Adicionando 1000000 elementos ao Vector...
A opera??o demorou 484 msecs.
Adicionando 1000000 elementos ao HashMap...
A opera??o demorou 7891 msecs.
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Note: This only times the for loop and insert into each one... not the lookup time and array stuff of the original..
Test One:
Uninitialized capacity for Vector and HashMap
import java.util.*;
public class SpeedTest
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} // SpeedTestAdministrator@WACO //c
$ java SpeedTest
Vector Time 331 msecs.
Map Time 90 msecs.
Test Two:
Initialize the Vector and HashMap capacity
import java.util.*;
public class SpeedTest
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} // SpeedTestAdministrator@WACO //c
$ java SpeedTest
Vector Time 60 msecs.
Map Time 90 msecs.
We see that IF you know the capacity of the vector before its usage, it is BEST to create one of the needed capacity...

Why is wireless performance faster than wired WRT54G v8?

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I have explation guys..why apple dual qure is faster than other quad qure devices?and appl 1g ram .is faster 2g of other devises?...i wish to get the reason

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Firefox seems/is faster than Safari but why?

I always found Safari to be faster than Firefox. Safari 4 compared to Firefox 3.5 seems slower. Some pages take forever to respond in Safari and don't in Firefox. I also think the screen now refreshes faster in Firefox. I've looked at the specs and Safari is supposed to be much faster but I don't seem to be experiencing it as so.
Although Firefox is nicer for the Mac in its 3.5 iteration, I'm used to Safari having used it since I returned to the Mac in 2003. Also, Firefox doesn't support the same level of services as Safari. In Safari, I'm constantly using services to grab info to SOHO Notes folders.
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Greetings,
The reasons behind your experience could be many, but try this to see if it improves things:
Quit Safari if it's running and open System Preferences>Network.
In the DNS Server tab, make sure IPv6 is turned off, and enter these two DNS servers to replace the ones you currently have:
208.67.222.222
208.67.220.220
click Apply Now and quit System Preferences.
Next, do these things in order:
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2. Go to Home/Library/Caches/com.apple.Safari and delete the contents of that folder.
3. Go to Home/Library/Caches/com.apple.Safari/Web Page Previews and delete the contents of that folder.
4. If you don't want to use the Top Sites feature, open Terminal and paste in this command:
defaults write com.apple.Safari DebugSnapshotsUpdatePolicy -int 2
5. Go to Home/Library/Caches/Metadata/Safari and delete the contents of that folder.
6. Go to Home/Library/Caches/Safari and delete the contents of that folder.
7. Go to Home/Library/Safari and delete these files (if you have them):
Downloads.plist
History.plist
Form Values
LastSession.plist
WebpageIcons.db
Repair Disk Permissions, then restart Safari and see if the speed is improved.

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I produce DVDs so my Compressor DVCam -> MPEG2 encoding is the most time consuming task. Take the MacWorld benchmarks, I was dissappointed the QC 2.66 was a third faster than a DC 2.7 G5 running Compressor.
I would have expected almost 2x as fast, basically halving encoding times. The Mac Pro took 107s vs G5 137s only 1.28x as fast OR put another way jobs complete in 78% of the time taken for the G5.
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G4 Dual Gigabit Mac OS X (10.4.7) ATI 9800 Pro

Terpstar,
I was wondering if you have had a chance to use Motion yet. I have a MBP, and using Zapfino fonts with SciFi Glow crashes my system every time. I would be interested to see if this is the case on other intel based systems. This has led to a failure of my main logic board twice over the last month. See my thread:
http://discussions.apple.com/thread.jspa?threadID=614641&tstart=25
Also, of the two GB ram I have installed, FCP doesn't seem to utilize more than 100MB of RAM. Although the VM size is several GB for the app. I noticed that in order to utilize both cores on my MBP, Airport had to be turned off.
Also, as Ned Snowing was saying, there is no doubt that there are going to be many software bugs that must be sorted out. Especially since this program is being adapted for intel macs, and not re-written.

Why is my MacBook downloading faster than my new Imac?

I have a two year old Macbook; 2.4 GHz Intel Core 2 Duo, 2GB 667 MHz DDR2 SDRAM with about 30GB left of memory. I also just purchased, from apple, a 27" Imac; 2.8 GHz Intel Core i7 with 4 GB 1067 MHz DDR3. and have just under 850GB left. The Macbook is running on 10.5.8 and the Imac is on 10.6.3.
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Macbook: Download 18.45Mb/s, Upload 2.28Mb/s, Ping 93
IMac: Download 20.88Mb/s, Upload 2.3Mb/s, Ping 89
I don't know if any of this information helps or if anyone will even read this far but the apple store is extremely far from my house and would try almost anything to fix this issue. My questions are:
1) Is this a known issue that has a fix, if so how do i fix it?
2) Is this possibly a faulty computer that i would have to return?
3) Is this the way it's supposed to operate and if I don't like it take it back
Thanks in advance for anyone who even reads this post.

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I do agree with the one comment about testing one computer at a time instead of simultaneously.
Also, when you said you have the movies from the Macbook on your iMac, can you elaborate? If you are using a shared library, then your iMac is going to be using part of your download speed for updates to your shared itunes library, where your Macbook is only going to be uploading the list. If I am incorrect in my understanding of the sharing of iTunes library, someone please let me know.

Why is my iMac 450/128 much, much faster than my Powerbook 333/512?

Hey boys and girls,
I'm sort of new to the Mac world, but I'm working hard to become clever.
So, here's the story. I have a Powerbook Bronze 333MHz with 512MB of RAM and the Toshiba 6GB drive it was born with and 10.3.9. I have a Bumbleberry (I think that's the "official" colour) iMac at work with a G3 at 450MHz and only 128MB of RAM also running 10.3.9.
The iMac runs much, much faster than the Powerbook, despite barely meeting the minimum RAM requirements of 10.3. What are some possible reasons for this? I understand that this ain't no speed machine, but the Powerbook is so slow that there is a second or two second typing delay in an Adium chat window for heaven's sake.
OK, so the iMac is technically faster, but I feel as though there is something wrong with the performance of the Powerbook, especially with all the RAM I've thrown at it (the Activity Monitor says that the PB has roughly 140MB of free RAM right now). I have a newer 40GB 5400 RPM drive that I'm tempted to install, to see if the 6GB drive is just old and tired (it whines a bit, so I'm sure it is to some degree) -- am I wasting my time?
Thanks for any help in advance.
Ugli
PB Bronze Mac OS X (10.3.9)

ugli:
Welcome to Apple Discussions.
You are well on the way to becoming clever. Really. Just by logging in and posting here you have started a process of learning that can go on until you are really clever.
There are a number of reasons your iMac seems faster that the Lombard. One is that it has a faster processor. Secondly, even with more RAM your Lombard has a small, slow HDD. I don't know how much free space there is on your HDD, but 6 GB fills up quite quickly these days. I am sure the larger (and faster) HDD will make a difference. I had maxxed out the RAM on my Pismo, but it was when I installed a larger, faster HDD that I noticed the difference. And, of course, when I upgraded the processor I noticed the biggest difference. Still not match for the newer faster machines, but then, I'm not as fast as I used to be either.
Good luck in your quest.
cornelius
PismoG4 550, 100GB 5400 Toshiba internal, 1 GB RAM; Pismo 500 OS X (10.4.5) Mac OS X (10.4.5) Beige G3 OS 8.6

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