Random Source

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Generates a number of samples of random numbers of [min, max) meaning the max value won't be included. Repeat samples if specified. Useful for creating bytes of information for testing a modulator.

Ex: With min=0 and max=2, the sequence 01110101... of length num_samps will be generated.

Supports an output of type int, short, and byte.

This block differs from Random Uniform Source:

This block uses Numpy to generate a fixed random vector of values. The output of this block repeats every num_samps, and hence has high autocorrelation with that period.
The algorithms used to generate the random numbers differ, as well: Numpy, and hence Random Source, use MT19937¹, whereas the Random Uniform Source uses XOROSHIRO128+, which has a period of 2128-1 and is hence to be preferred if autocorrelation over a window of length num_samps is relevant.

This block does not support C++ output, so it cannot be used when the output language of a flowgraph in GRC is C++.


(R): Run-time adjustable

Output type
Available options are int, short or byte
The lower limit of the range of generated values (included in the output)
The upper limit of the range of generated values (not included in the output)
Num Samples
Total number of samples that are generated in the output

Example Flowgraph


Source Files

C++ files
Header files
Public header files
Block definition

Computational Performance

File:Benchmark prng.grc done on a Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz, 8GB RAM VOLK 2.5.0, GNU Radio, Linux 5.15.11

Benchmark prng.png

Block Number of Samples / Period after which samples repeat Throughput (in 106 samples per second) Note
Random Source 1000 838 default setting
Random Source 220=1,048,576 824
Random Source 224 812
Random Source 228 813 Initialization of the random vector needs nearly 30s, eats 4GB of RAM
Random Uniform Source 2128-1 282

¹ The slightly superior randomness properties of MT19937 over XOROSHIRO128+ don't matter within the maximum size of a vector of values on a PC, and are generally unnoticable in an SDR contex