Add an LFSR module #5
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AngelEzquerra
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This module, which is heavily based on Nikesh Bajaj's pylsfr (https://pylfsr.github.io), implements a Linear Feedback Shift Register that can be used to generate pseudo-random boolean sequences. It supports both Fibonacci and Galois LFSRs. LFSRs are used in many digital communication systems (including, for example LTE and 5GNR). For more information see https://simple.wikipedia.org/wiki/Linear-feedback_shift_register
impulse/lfsr.nim
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| # Remove the last value from taps if it is a zero | ||
| let taps = if taps[taps.size - 1] == 0: taps[_..^2] else: taps | ||
| if taps.size > 1 and taps[0] < taps[taps.size - 1]: |
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Doesn't this mean for multiple polynomials an ordering like [7, 3, 5, 2] would pass the check? If so one could use isSorted (https://nim-lang.github.io/Nim/algorithm.html#isSorted%2CopenArray%5BT%5D)
impulse/lfsr.nim
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| ## - taps: Feedback polynomial taps as a Tensor[int] of exponents in | ||
| ## descending order. Note that exponent 0 can be omitted, since it is | ||
| ## always implicitly added. For example, to use the `x^5 + x^3 + 1` | ||
| ## polinomial you can set taps to `[5, 3].toTensor` or to |
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| ## polinomial you can set taps to `[5, 3].toTensor` or to | |
| ## polynomial you can set taps to `[5, 3].toTensor` or to |
impulse/lfsr.nim
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| self.count += 1 | ||
| self.outbit = result | ||
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| return result |
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Not really needed (the python heritage shines through 🤣)
AngelEzquerra
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Improve handling of seqs. Co-authored-by: Vindaar <[email protected]>
impulse/lfsr.nim
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| iterator generator*(lfsr: var LFSR,n: int, | ||
| store_sequence: static bool = false): bool = | ||
| ## Generator that will generate a random sequence of length `n` | ||
| ## | ||
| ## Inputs: | ||
| ## - Preconfigured LFSR object | ||
| ## - n: Number of random values to generate | ||
| ## - store_sequence: static bool that enables saving the generated sequence | ||
| ## | ||
| ## Return: | ||
| ## - Generated boolean values | ||
| yield lfsr.next(store_sequence = store_sequence) |
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I don't quite understand why this is an iterator. The iterator only returns a single element. So it might as well just be a procedure? Calling it in a for loop will be redundant, no?
And it doesn't loop over n either so that next is called n times. Oversight or intended?
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I renamed the iterator to items, fixed the problem you explained and added a couple of new arguments to make it more flexible. Those new options might be overkill though :-). If you feel they are too much please let me know and I'll remove them.
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Can't much comment on the logic in |
This module, which is heavily based on Nikesh Bajaj's pylsfr (https://pylfsr.github.io), implements a Linear Feedback Shift Register that can be used to generate pseudo-random boolean sequences. It supports both Fibonacci and Galois LFSRs.
LFSRs are used in many digital communication systems (including, for example LTE and 5GNR). For more information see https://simple.wikipedia.org/wiki/Linear-feedback_shift_register