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Remove quadratic time complexity in Statement.cast() #634

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antonblanchard
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@antonblanchard antonblanchard commented Sep 27, 2021

Using sum(lst, []) to flatten a list of lists has quadratic time
complexity. Use chain.from_iterable() instead. While not strictly
necessary to improve performance, convert to map().

A test case writing out verilog for a 512k entry FIFO is 120x faster
with this applied.

Using sum(lst, []) to flatten a list of lists has quadratic time
complexity. Use chain.from_iterable() instead. While not strictly
necessary to improve performance, convert to map().

A test case writing out verilog for a 512k entry FIFO is 120x faster
with this applied.
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@whitequark whitequark left a comment

LGTM, nice catch!

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codecov bot commented Sep 27, 2021

Codecov Report

Merging #634 (e62ef89) into master (9834b7e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Impacted file tree graph

@@           Coverage Diff           @@
##           master     #634   +/-   ##
=======================================
  Coverage   81.47%   81.47%           
=======================================
  Files          49       49           
  Lines        6450     6451    +1     
  Branches     1287     1286    -1     
=======================================
+ Hits         5255     5256    +1     
  Misses       1008     1008           
  Partials      187      187           
Impacted Files Coverage Δ
nmigen/hdl/ast.py 90.00% <100.00%> (+0.01%) ⬆️

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@whitequark whitequark merged commit 9f78ac0 into amaranth-lang:master Sep 27, 2021
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2 participants