feefrac: drop comparison and operator{<<,>>} for sorted wrappers #34669

1. 
   sipa commented at 4:39 PM on February 25, 2026: member

   Instead of having an unintuitive but strong implicit sort order on FeeFrac (first increasing feerate, then decreasing size), and separate overloaded operator<< and operator>> that implement a weak ordering that only looks at feerate, replace these with explicit wrapper classes which make the behavior more explicit (ByRatio and ByRatioNegSize).

   This allows for things like ByRatio{a} <= ByRatio{b}, instead of the earlier !(a >> b). It also supports usage inside std::min/std::max/std::less, and std::greater, so one can use:

   • std::max<ByRatioNegSize<FeeFrac>>(a, b) to get the highest-feerate FeeFrac, tie-breaking by smallest size.
   • std::ranges::sort(v, std::greater<ByRatioNegSize<FeeFrac>>{}); to sort a vector that way.

   Suggested in #34257 (review).

2. 
   sipa commented at 4:39 PM on February 25, 2026: member

   Not intended for 31.0.

3. 
   DrahtBot commented at 4:39 PM on February 25, 2026: contributor

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   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #34803 (mempool: asynchronous mempool fee rate diagram updates via validation interface by ismaelsadeeq)
   • #33966 (refactor: disentangle miner startup defaults from runtime options by Sjors)

   If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

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4. in src/test/fuzz/txgraph.cpp:436 in 38e70ff287

    432 | @@ -433,7 +433,7 @@ FUZZ_TARGET(txgraph)
    433 |          assert(num_tx == sim.GetTransactionCount());
    434 |          // Sort by feerate only, since violating topological constraints within same-feerate
    435 |          // chunks won't affect diagram comparisons.
    436 | -        std::sort(chunk_feerates.begin(), chunk_feerates.end(), std::greater{});
    437 | +        std::sort(chunk_feerates.begin(), chunk_feerates.end(), std::greater<ByRatioNegSize<FeeFrac>>{});
   

   ---

   ---

   

   andrewtoth commented at 5:37 PM on February 25, 2026:

   Since we're touching all these std::sort, we can also update them to C++20 ranges:

           std::ranges::sort(chunk_feerates, std::greater<ByRatioNegSize<FeeFrac>>{});
   

   ---

   

   sipa commented at 6:18 PM on February 25, 2026:

   Added an extra commit that uses std::ranges::sort and std::ranges::unique wherever possible in the cluster linearization related files (not only in lines touches by the previous commit).

5. in src/test/feefrac_tests.cpp:86 in 64b81ff965

     96 |      // "empty" comparisons
     97 | -    BOOST_CHECK(!(p1 >> empty)); // << will always result in false
     98 | -    BOOST_CHECK(!(p1 << empty));
     99 | -    BOOST_CHECK(!(empty >> empty));
    100 | -    BOOST_CHECK(!(empty << empty));
    101 | +    BOOST_CHECK(!(ByRatioNegSize{p1} > ByRatioNegSize{empty})); // << will always result in false
   

   ---

   ---

   

   w0xlt commented at 10:45 PM on February 25, 2026:

   It is replacing BOOST_CHECK(!(p1 >> empty));.

       BOOST_CHECK(!(ByRatio{p1} > ByRatio{empty}));
   

   ---

   

   sipa commented at 1:38 PM on February 27, 2026:

   Fixed.

6. in src/util/feefrac.h:15 in 64b81ff965

     14 | @@ -15,26 +15,6 @@
     15 |  /** Data structure storing a fee and size, ordered by increasing fee/size.
   

   ---

   ---

   

   w0xlt commented at 10:47 PM on February 25, 2026:

   nit: FeeFrac no longer has comparison operators.

   /** Data structure storing a fee and size.
   

   ---

   

   sipa commented at 1:38 PM on February 27, 2026:

   Done.

7. in src/util/feefrac.cpp:45 in 64b81ff965

   ---

   ---

   

   w0xlt commented at 11:01 PM on February 25, 2026:

   It seems the code is implicitly converting std::strong_ordering to std::weak_ordering.

   -        std::weak_ordering cmp = std::weak_ordering::equivalent;
   +        std::strong_ordering cmp = std::strong_ordering::equivalent;
   

   ---

   

   sipa commented at 1:38 PM on February 27, 2026:

   Done, and switched to auto to avoid repeating the type name.

8. feefrac: drop comparison and operator{<<,>>} for sorted wrappers

   Instead of having an unintuitive but total implicit sort order on
   FeeFrac (first increasing feerate, then decreasing size), and separate
   overloaded operator<< and operator>> for a weak ordering that only looks
   at feerate, replace these with explicit wrapper classes which make the
   behavior more explicit.
   
   This allows for things like ByRatio{a} <= ByRatio{b}, instead of the
   earlier !(a >> b). It also supports usage inside std::max and
   std::greater, so one can use:
   * std::max<ByRatioNegSize<FeeFrac>>(a, b)
   * std::sort(v.begin(), v.end(), std::greater<ByRatioNegSize<FeeFrac>>{})

   747da25360
9. clusterlin: adopt STL ranges algorithms (refactor) 1aa78cdab6
10. sipa force-pushed on Feb 27, 2026
11. 
    ajtowns commented at 11:04 AM on March 2, 2026: contributor

    Maybe demote this to draft until 31 is branched off?

12. sipa marked this as a draft on Mar 2, 2026
13. fanquake added this to the milestone 32.0 on Mar 2, 2026
14. sipa marked this as ready for review on Mar 12, 2026
15. 
    sipa commented at 1:38 PM on March 12, 2026: member

    Marked ready for review with 31.x branched off.

16. sedited approved
17. 
    sedited commented at 9:12 PM on March 23, 2026: contributor

    ACK 1aa78cdab6bc8ecd4448b1b75ee3181ee8f3f519

18. sedited requested review from ismaelsadeeq on Mar 23, 2026
19. 
    ismaelsadeeq commented at 7:00 AM on March 24, 2026: member

    Concept ACK

Contributors

sipaDrahtBotandrewtothw0xltajtownsseditedismaelsadeeq

Review Requested
ismaelsadeeq

Milestone
32.0