Re: [Discuss-gnuradio] What factor determines input_item size (ninput_items)?

Hi Jeon,

What factor determines input_item size (ninput_items)?

these are two things: the input item size is the size of a single item, and ninput_items is the amount of items that your (general_)work call sees.

You are referring to the second thing:

Consider this flow graph:

A -> B -> C

A is the upstream block (e.g. USRP source), B is your block, and C is a downstream block (e.g. Vector sink).

ninput_items is determined by how many samples are available. Your block B has no influence on it; whenever the upstream block A finishes doing its (general_)work, GNU Radio updates the number of items available in the buffer between A and B. It then asks B whether it wants to work on this amount of input samples.

I see your forecast method, and it seems to do the right thing: If your block is in the SYNC state, to output anything, it needs 480 items. If there's no 480 input items, GNU Radio won't call your general_work, usually. You should try printing ninput_items, to see if that's correct.

Now, your block has two input streams. If they are somehow related, timing and buffer sizes might actually lead to a deadlock situation. Can you give us an overview over the whole flowgraph?

Best regards,
Marcus

On 28.08.2015 19:00, Jeon wrote:

I am testing my OOT module in various condition of different machines.

A certain block implementing a state machine requires a certain number of items or more.

Thus, I've stated it in forecast():
https://gist.github.com/gsongsong/9ba1cb974a57a0861678#file-forecast-my_block-cpp

In general work(), the block determines how many items it should be consume:
https://gist.github.com/gsongsong/9ba1cb974a57a0861678#file-general_work-my_block-cpp

With these codes, it works find with my own machinie.

Ubuntu 14.04, 2 CPUs and 4 GB RAM allocated virtual machine. The host has i7-3770 and 16 GB RAM.

But it fails on machine that my school gave to me for educational and research purposes. I can't tell you the exact spec. of the machine, but it apparently has a poor CPU and a lower memory space.

Do these difference on machines' specs affect on ninput_items? I think they have a certain relation to each other... since GNU Radio scheduler allocates available memory over all blocks...? If so, can it be resolved if I manually set a larger memory/buffer size to GNU Radio? (If my memory is correct, I remember there's a configuration file to do it...)

Regards,

Jeon.

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