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Re: [Discuss-gnuradio] Strange output of "0" at the terminal

From: mleech
Subject: Re: [Discuss-gnuradio] Strange output of "0" at the terminal
Date: Fri, 24 Feb 2012 11:50:19 -0500
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Modern disk subsystems can easily sustain 80MB or more per second even on relativley wimpy hardware

What is the sample rate involved here?  Seriously, I've been able to stream multi-MHz of bandwidth to disk for long periods without any 'O' happening.


On Fri, 24 Feb 2012 11:23:05 -0500, Andrew Davis wrote:

You are writing to a file in a blocking thread, its not the CPU it's
the hard drive. You should try the program without the write. Then if
it is the problem you should write out to a file on a ram disk then
save it to a real disk later.

2012/2/24 Wu Ting <address@hidden>:
Hi! Thank you for your suggestions! I realized it is a problem related with computer speed. Today I used a laptop to run the same code, and 'O' is printed much more frequently. However, the computer I'm using is a quite good one. It has intel i7 3.4GHz 8-core, and when the code is running, CPU is only used by about 10%, and memory is also used by no more than 15%. On the other hand, I also checked number of messages in message queue, and I've found that when 'O' is printed, sometimes there are only several messages in the queue. So I don't understand why it has this outflow problem. And is it possible to catch this error when it happens, so that I can deal with it in the problem? Thanks! Wu
2012/2/23 Wu Ting <address@hidden>
Hi! Thank you for your response. I've kept working on this problem for two days, but still cannot find a way to solve it. I simplified the program and have determined that the 'O' is produced is this while loop: while msgCount<10000:    msg = tb.queue.delete_head()    payload = msg.to_string()    f.write(payload)    msgCount += 1 I also tried to make it sleep for a short time after each operation: while msgCount<10000:    msg = tb.queue.delete_head()    sleep(0.00001)    payload = msg.to_string()    sleep(0.00001)    f.write(payload)    sleep(0.00001)    msgCount += 1
Two quick things. First, the tb.queue.delete_head() is a blocking call, so it will wait until there is a message to process. You don't need to sleep. Adding a sleep call here is probably only making things worse since you're already not keeping up with the samples. Second, the sleep() call is generally only accurate to about ~10 ms, but you're asking it to sleep for 10 us. I'm not sure if it rounds up or down. Worse case, you're making the loop sleep for about 30 ms total; best case is you actually aren't pausing at all. Tom
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