FFT1M option only works up to 131072 FFTs

Quote from AdminTC on 10/08/2021, 11:42

You need to adjust the DSP Memory Model (Titelbar under Extras -> Configuration): The default is set to "Medium" which limits the maximum FFT size to 131072 FFTs.

You need to set it to "Large" for a 1M FFT:

 

BTW: Setting it to "Small" will reduce it to 32768 FFTs,

 

 

Quote from David3542 on 11/08/2021, 08:15

Quote from AdminTC on 10/08/2021, 11:42

You need to adjust the DSP Memory Model (Titelbar under Extras -> Configuration): The default is set to "Medium" which limits the maximum FFT size to 131072 FFTs.

You nee to set it to "Large" for a 1M FFT:

 

BTW: Setting it to "Small" will reduce it to 32768 FFTs,

 

 

 

Thanks you ! ,now  it works fine

Quote from aminucd on 16/02/2023, 21:26

Hi,

I upgraded our device, RSA 250X to 245MHz RTBW. It, however, freezes when I use it with 1M FFT. I use boost cable and DSP memory is ludicrous.

Please also see the screenshot. Thanks for the help.

Best, Amin

Quote from mm_dev on 17/02/2023, 10:53

Check the warnings for the yellow Boost and Rx status indicators in the V6 block. Also look at system memory consumption, very high FFT values may consume a lot of memory which can cause problems if your system cannot handle that (which is why the default memory model is set to medium).

If that doesn't help, please attach the mission your're using including all modifications you've made. The screenshot lacks a lot of relevant information and the values that can be seen don't match.

Quote from aminucd on 27/02/2023, 18:57

Hi,

Please find the mission in the attached file. With 1M FFT it only works with 122MHz RTBW. For 245MHz it freezes. I've selected Ludicrous memory with changing  DSP threats from 0-8 but no success. The Boost connection are also in use.

Thanks

Best, A.

Quote from mm_dev on 28/02/2023, 10:28

Combining 245 MHz RTBW and 1M FFT results in a massive CPU load. And unfortunately the IQ conversion at this point cannot make use of multiple threads, so this requires a CPU with extremely high single-thread performance. At the moment, only the most recent Intel desktop CPUs like the 13900K can handle this (even a 12900K isn't quite up to the task). I assume the latest generation of AMD desktop CPUs may work as well, but we haven't been able to test those yet.

When your CPU cannot handle the load, the RTSA will buffer data that cannot be processed in time. This will result in increased memory consumption, and depending on your actual system specs you may eventually run out of memory, at which point the application may freeze (haven't been able to reproduce that here, but as said this depends on system specs). This could potentially happen very quickly as the V6 generates almost 2 GB/s of data when streaming 245 MHz IQ.

Either reduce your bandwidth, your span factor or reduce the FFT setting to a more reasonable number, until the "CPU Sat" indicator in the bottom right corner of the RTSA window gets below 100% constantly.

And as always, make sure you're using the most recent RTSA version. The mission reports version 10815, which is pretty old at this point.

Quote from aminucd on 28/02/2023, 23:47

Hi,

Thank you for the reply.

-RSA 250X that we have works well with 122MHz RTBW and 1M FFT .

-It , however, freezes with 245 MHz RTBW with any FFT higher than 8192 FFT!

If the CPU limit is the issue, I assume that the 245MHz RTBW should have worked with 512K FFT. Can you check this on the mission that I've sent and fix the issue?

Best, A.

 

 

Quote from mm_dev on 01/03/2023, 11:27

First, as already stated before, you have warnings for both Rx and Boost connection. Have those disappeared? If not, you really need to check the actual error messages associated with those (should show up as a tooltip when you point the mouse cursor over them). While I can guess what the Rx issue is (CPU overload), the Boost connection needs to work properly if you want to use 245 MHz in general, else all bets are off.

The relation between FFT and RTBW isn't linear, reducing bandwidth doesn't automatically mean you can increase FFT by the same factor. Though if 1M works fine with 122 MHz you should be able to use more than 8k with 245 MHz.

As said, I can't reproduce the freeze at all (using the provided mission, on any RTSA version and with multiple devices). 245 MHz RTBW works fine in general, just with the limitation regarding FFT size stated above (which shouldn't cause an instant freeze anyway). So apparently something specific to your system is triggering it. Can you provide your system specs (CPU, memory, graphics card, storage, chipset, ...) so we can try to narrow it down? If we can't reproduce it the chance of fixing it is rather small.

Also please check performance metrics (CPU utilization, memory usage, if possible CPU clockspeed or power consumption) of your system before and when the freeze occurs.