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Test FFT Speed, LV7.1 vs. LV8.20


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If I remember correctly, there was supposed to be a speed enhancement in some of the math functions between LV7.1.1 and LV8.x. I don't currently have access to LV8.x. Could someone please run the attached VI in both 7.1 and 8.x and let me know the speed results?

Thanks,

Gary

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QUOTE(French LVer @ Mar 15 2007, 11:11 AM)

Tested on an Intel Pentium M 1.7 GHz 512 Mo.

For 10 FFT

=> LV 7.1 : 126.5 to 128.2 ms

=> LV 8.2 : 143.6 to 145.0 ms

Might be better on a real computer :rolleyes:

Thank you very much!

I have to say that you have managed to raise more questions than answers...

My results are:

LV7.1.1 2.4GHz P4 , 2GB RAM, lots of other crap open: 249 ms. EDIT: WinXP Pro SP2.

LV7.1.1 2.4GHz Dual Xeon, 1GB RAM: 274 ms. EDIT: Win2k SP3.

Questions:

Why is yours twice as fast as mine?

Why is your LV7.1 faster than LV8.2?

Why is my P4 with lots of stuff in the background faster than my Xeon?

:wacko:

Anyone have any thoughts?

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Thanks to those who ran this for me. I guess I haven't yet confirmed whether LV8.x FFT is faster than the LV7.1.1 version, but I did notice something interesting.

I've attached a new vi that runs the one I posted above and plots runtime as function of FFT length. On my system, runtime starts to increase more-or-less linearly after 128kpoints.

I'm guessing, therefore, that below 128kpoints most of the time is spent doing the FFT, and I can see the logN part of the execution time. Above 128kpoints FFT, Labview is spending more time doing memory allocation than actually performing the calculations, so I'm mostly seeing a linear increase in time it takes to do the buffer allocation.

All you guys with the faster times than me probably have faster memory, or at least a faster memory bus.

Does that sound reasonable?

Gary

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Gary:

I ran your original vi on my older Dell Precision 370 2.8GHz single core (circa 8-2004), 512M RAM (185M free) LV8.2 Win XP SP2. 81-82msec consistently (FASTER)

The original test I ran was on a Precision 380 circa 5-2005

I do not know RAM specifics, but using AIDA32 I did memory Read/Write tests.

Pecision 370: Read 5274MB/sec, Write 2081MB/sec

Precision 380: Read 5578MB/sec, Write 2152 MB/sec.

Do not know why the slower 370 memory executes faster.

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