# Is there possible to have item drops? **URL:** \ **Category:** GNU Radio\ **Created:** [October 15, 2014, 6:08pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544 "2014-10-15T18:08:56Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [October 15, 2014, 6:08pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544/1 "2014-10-15T18:08:56Z")
Hi all, It seems this is a ridiculous question, however, I didn’t find any solution for my problem. I have already a bunch of custom blocks connected to each other which play role as a transmitter (tx). I want to connect tx to a fir filter by using fir\_filter\_ccc block. I set the filter taps with specific ones. I also have this filter in Matlab. The output of the filter is connected to a sink file. When I see the output (tx) and filtering it by Matlab and comparing it with the output of the gnuradio filter, I see both of the following: 1. Both matlab and gnuradio filtered output, have little difference in a range of 0.01. (I’m using gr\_complex data). 2. After a while, Matlab output and GNURadio’s output will differ as high as 1000 in magnitude!! I guess, there is item drops in this filtering. I know, the probability of this event is so weak, anyway, item drop even can happen in GNURadio? Where is my problem? Best, Mostafa ---
**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\ **Post date:** [October 15, 2014, 7:35pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544/2 "2014-10-15T19:35:23Z")
Hello Mostafa, filtering is a inherently lossy operation: it’s an operation that involves multiplication and addition of floating point numbers. Matlab internally uses double (float64) values, whereas GNU Radio, usually, uses single precision (float32) numbers for performance reasons. Now, without knowing what kind of signal you are filtering with what kind of taps you are using with what kind of GNU Radio filters and what Matlab functions, there’s nothing to guess on how these differences occur. What I _can_ say though is that I’ve never seen an item drop in GNU Radio’s runtime, and we have strong tests against that. Now, it’s entirely possible that any of our filter implementations might have bugs, but I kind of doubt that. It’s most probably simply numeric accuracy that kills your samples. Greetings, Marcus ---
**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\ **Post date:** [October 16, 2014, 1:48pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544/3 "2014-10-16T13:48:12Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) ---
**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\ **Post date:** [October 16, 2014, 2:47pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544/4 "2014-10-16T14:47:45Z")
I’m a bit confused. Your diagram TX-\>FIR-\>… -\>Filesink Indicates that TX is a source, whereas TX usually is an information sink in DSP. Maybe you want to fill us in about the type of block TX is? Greetings, Marcus ---
**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\ **Post date:** [October 16, 2014, 10:04pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544/5 "2014-10-16T22:04:10Z")
Tx is an abbreviation of tx blocks! 🙂 I finally found the problem! I used heap memory but I never release it in different blocks! So during the runtime, the memory allocation get the error: “std::bad\_alloc” after somewhile. Now this is fine. Thank you too much, Best, Mostafa On Thu, Oct 16, 2014 at 4:16 PM, Marcus M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > something > > > Best, > > > > > multiplication and addition of floating point numbers. > > > entirely > > > > > > role as a transmitter (tx). I want to connect tx to a fir filter by > > > > > > 1. Both matlab and gnuradio filtered output, have little difference in a > > > Where is my problem? – * * * Department of Electrical Engineering Aboureyhan Building MMWCL LAB Amirkabir University Of Technology Tehran IRAN Tel: +98 (919) 158-7730 LAB: [http://ele.aut.ac.ir/~mmwcl/?page\_id=411](http://ele.aut.ac.ir/~mmwcl/?page_id=411) Homepage: [http://ele.aut.ac.ir/~alizadeh/](http://ele.aut.ac.ir/~alizadeh/) * * * ---
**Author:** ![mostafa\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mostafa\_a](https://www.ruby-forum.com/u/mostafa_a)\ **Post date:** [October 16, 2014, 10:26pm UTC](https://www.ruby-forum.com/t/is-there-possible-to-have-item-drops/232544/6 "2014-10-16T22:26:12Z")
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 16.10.2014 22:02, Mostafa A. wrote: > Tx is an abbreviation of tx blocks! 🙂 > That still doesn’t make sense! 🙂 > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1 iQEcBAEBAgAGBQJUQCmHAAoJEAFxB7BbsDrLQs0H/R4afmR6XubcaN1qJAleVqiJ Av6jkaWf1aNBMqoYgmoBjj8Ad4Hwkek5Uz7TElMtSkpxtlRwcdayXyoTprh0X5yD yKiIK1nizSdoddsagZv3DngI3XPaLhrOtg9C6OJwHTXNSdSFyGP8I0cPeCTw+Vtm XgektLgKZEJBiujbLhu3Sr3rMN5deI9KcONkiza8wEduuG4UzFyqrOUBqgZ91kmT MoEjoP0cH4xdOviLfHs6r+SFauP9ov2UA+nf/jvhYV208jOY4+txnmeHJFh+f+qk wy0dqNEa6Ccip6SZdL90wRjZOue1bye2js6uM18HEpGCu8dUcu9aT68WdHPL3LY= =mt/k -----END PGP SIGNATURE-----