# FW: output operand requires a reduction, but reduction is not enabled

**URL:** <https://www.ruby-forum.com/t/fw-output-operand-requires-a-reduction-but-reduction-is-not-enabled/239723>\
**Category:** GNU Radio\
**Created:** [March 11, 2014, 11:37pm UTC](https://www.ruby-forum.com/t/fw-output-operand-requires-a-reduction-but-reduction-is-not-enabled/239723 "2014-03-11T23:37:14Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [March 11, 2014, 11:37pm UTC](https://www.ruby-forum.com/t/fw-output-operand-requires-a-reduction-but-reduction-is-not-enabled/239723/1 "2014-03-11T23:37:14Z")

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From: David Halls  
Sent: 11 March 2014 16:10  
To: Martin B.; removed\_email\_address@domain.invalid  
Subject: RE: [Discuss-gnuradio] output operand requires a reduction, but  
reduction is not enabled

Hi,

Yes, the len(output\_items[0]), is either 1 or 2…

If I set\_output\_multiple to 10, then this value raises to 10.

It is dominated by the fact that one of the inputs to my block is much  
lower than the other?? Input[0] is the data stream and has say 768  
items, input[1] is the packet average SNR, so it only has 1 or 2 items  
in the same period.

Forecast is currently

```
    For I in range (len(ninput_items_required)):
            Ninput_items_required[i] = noutput_items

```

Does this need to be altered for my case where I have two inputs with  
very different requirements.

If I ever get my head around the scheduler in GNU radio, it will be a  
happy day 🙂

D