11253776824
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Ran 09 Oct 2024 11:19AM UTC

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Files 21

Run time 1min

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Committed 09 Oct 2024 11:12AM UTC coverage: 100.0%. Remained the same

Build # 11253776824

Build Type

push

github

Committed by

web-flow

Commit Message

Improve field count typical case performance (#120)

The tightest upper bound one can specify on the number of fields in a
struct is `sizeof(type) * CHAR_BIT`. So this was previously used when
performing a binary search for the field count. This upper bound is
extremely loose when considering a typical large struct, which is more
likely to contain a relatively small number of relatively large fields
rather than the other way around. The binary search range being multiple
orders of magnitude larger than necessary wouldn't have been a
significant issue if each test was cheap, but they're not. Testing a
field count of N costs O(N) memory and time. As a result, the initial
few steps of the binary search may be prohibitively expensive.

The primary optimization introduced by these changes is to use unbounded
binary search, a.k.a. exponential search, instead of the typically
loosely bounded binary search. This produces a tight upper bound (within
2x) on the field count to then perform the binary search with.

As an upside of this change, the compiler-specific limit placed on the
upper bound on the field count to stay within compiler limits could be
removed.

Run Details

407 of 407 relevant lines covered (100.0%)

9346.72 hits per line

Jobs

ID	Job ID	Ran	Files	Coverage
1	11253776824.1	09 Oct 2024 11:19AM UTC	21	100.0	GitHub Action Run

boostorg / pfr / 11253776824
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