Bit functions: refactoring, extension, and optimisation - #23
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synesissoftware wants to merge 13 commits into
Open
synesissoftware wants to merge 13 commits into
synesissoftware wants to merge 13 commits into
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Replace the short separator above each namespace close with the long section banner, and drop the short separator that precedes the include-guard close: - Refresh **Updated:** to 24th September 2026 and extend the Synesis Information Systems copyright through 2026; - Bump each header **EDIT** counter;
Expand **test.unit.stlsoft.util.bit_functions** so every public C++ overload is called for each supported width, plus `count_bits(int)` for signedness; - Add Kernighan and 8-bit-table cases for **uint64_t**; - Add **count_bits** for **uint32_t**, **uint64_t**, and **int**; - Add **find_highest_bit** for **uint8_t** and **uint16_t**; - Add **calculate_xor_over_range** for 16-, 32-, and 64-bit ranges; - Remove in-unit stopwatch timing;
Add **test.performance.stlsoft.bit_functions** under a nested **stlsoft/** performance tree, with an aligned width × function timing table covering every public bit-function overload; - Wire **test/performance/CMakeLists.txt** → **stlsoft** → **bit_functions**; - Time Kernighan and 8-bit-table popcount, **count_bits**, **find_highest_bit**, and **calculate_xor_over_range**;
…Kernighan` is defined
Extend **test.performance.stlsoft.bit_functions** with denser popcount workloads so Kernighan vs 8-bit-table can be compared beyond the sparse sequential-i series; - Add /~i (bitwise-not), /ones (volatile all-ones), and /ones^1 (all-ones with one rotating bit cleared); - Widen the function-name column for the longer row labels;
Stop importing stlsoft::uint64_t into the global namespace: it conflicts with ::uint64_t from <cstdint> (pulled in via std_chrono_hrc_stopwatch) and made 64-bit overloads ambiguous on Linux GCC. - Use stlsoft::ss_uintN_t aliases for variables and casts; keep column headers as uintN_t labels;
Time each row as one discarded warmup plus five samples and print the median. Accumulate the anchor in ss_uint64_t. Print STLSOFT_COMPILER_VERSION_STRING, whether optimisation is size, speed, or off, and whether this is a release or debug-asserts build.
Zero-initialise the local sorted[] buffer in median_sample, guard empty n, and clamp n to NUM_SAMPLES so GCC -Werror=maybe-uninitialized no longer fails the performance harness on CI.
GarthJL1965
approved these changes
Sep 24, 2026
Add volatile-zero, rotating-bit, and both-halves-live rows for popcount and find_highest_bit, so the 64-bit high half is exercised. Print ns/call on the same line as the loop time, ns/element for XOR, and the anchor last. Honor SIS_PERFTESTS_GROUPGAPS with a blank line between operation and input-pattern groups.
Keep the 8-bit table as the default for count_bits(). Apple Clang rewrites Kernighan into a hardware popcount; Linux and Windows compilers execute the source loop and the table is faster there.
Add unselected `count_bits_by_intrinsic()` / `find_highest_bit_by_intrinsic()`, with external/internal bitfns detection (GCC/Clang builtins preferred over MSVC), 8/16-bit count overloads, Clang `STLSOFT_CLANG_VER`, unit and performance coverage, and strategy notes that keep the 8-bit table as the `count_bits()` default;
Cast MSVC `__popcnt64` through `STLSOFT_C_CAST(int, …)` so `/WX` builds stop on C4244. Export `SIS_PERFTESTS_GROUPGAPS=1` for the performance job and only print the harness banner when that env is truey. Quiet getenv C4996 and narrow `~` promotions on uint8/16 ones patterns. Record Linux GCC 13.3 (~3.1 ns soft popcount vs table) and Apple Clang 21 CI findings in `strategy/BIT_FUNCTIONS.md`.
mwsis
approved these changes
Sep 27, 2026
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