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Fixed BitArray find returning runs that overlap set bits, and missing existing runs. (#459)

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This commit is contained in:
Branimir Karadžić
2026-10-15 09:45:32 -07:00
committed by GitHub
parent d4e6ed3cf4
commit a361ff7878
2 changed files with 142 additions and 61 deletions
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111
tests/bitarray_test.cpp
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@@ -8,6 +8,8 @@
#include <bx/allocator.h>
#include <bx/bitarray.h>
#include <bx/math.h>
#include <bx/rng.h>
#include <bx/string.h>
static void testRange(bx::MutableBitArrayView& _bs, uint32_t _beginBit, uint32_t _endBit)
{
@@ -976,3 +978,112 @@ TEST_CASE("BitArray-ranges-ending-on-word-boundary", "[container]")
REQUIRE( (UINT64_MAX >> 36) == (words[1] >> 36) );
REQUIRE( (UINT64_MAX >> 28) == words[2]);
}
static uint32_t findRef(const bx::MutableBitArrayView& _bs, uint32_t _beginBit, uint32_t _endBit, uint32_t _numBits)
{
for (uint32_t ii = _beginBit; ii + _numBits <= _endBit; ++ii)
{
if (_bs.testNone(ii, ii + _numBits) )
{
return ii;
}
}
return bx::kInvalid;
}
TEST_CASE("BitArray-find-random", "[container]")
{
constexpr uint32_t kNumBits = 1024;
uint64_t bits[kNumBits/64];
bx::MutableBitArrayView bs(bits, sizeof(bits) );
bx::RngMwc rng;
for (uint32_t iter = 0; iter < 20000; ++iter)
{
const uint32_t density = rng.gen() % 4;
bs.clear();
for (uint32_t ii = 0, num = 4 + rng.gen() % 64; ii < num; ++ii)
{
const uint32_t begin = rng.gen() % kNumBits;
const uint32_t end = bx::min(kNumBits, begin + 1 + rng.gen() % (8 << density) );
bs.set(begin, end, true);
}
for (uint32_t ii = 0, num = rng.gen() % 32; ii < num; ++ii)
{
const uint32_t begin = rng.gen() % kNumBits;
const uint32_t end = bx::min(kNumBits, begin + 1 + rng.gen() % 64);
bs.set(begin, end, false);
}
const uint32_t numBits = 1 + rng.gen() % 160;
const bool full = 0 == (rng.gen() & 3);
const uint32_t beginBit = full ? 0 : rng.gen() % (kNumBits - numBits);
const uint32_t endBit = full ? kNumBits : beginBit + numBits + rng.gen() % (kNumBits - beginBit - numBits + 1);
const uint32_t expected = findRef(bs, beginBit, endBit, numBits);
const uint32_t idx = full ? bs.find(numBits) : bs.find(beginBit, endBit, numBits);
INFO("Iteration " << iter << ", range [" << beginBit << ", " << endBit << "), num bits " << numBits << ", found " << idx << ", expected " << expected);
REQUIRE( (bx::kInvalid == idx) == (bx::kInvalid == expected) );
if (bx::kInvalid != idx)
{
REQUIRE(beginBit <= idx);
REQUIRE(idx + numBits <= endBit);
REQUIRE(bs.testNone(idx, idx + numBits) );
}
}
}
TEST_CASE("BitArray-find-skips-full-byte", "[container]")
{
uint64_t bits[1];
bx::MutableBitArrayView bs(bits, sizeof(bits) );
bs.set(0, 64, true);
bs.set(5, 8, false);
bs.set(16, 23, false);
REQUIRE(bx::kInvalid == bs.find(10) );
REQUIRE(16 == bs.find(7) );
}
TEST_CASE("BitArray-find-bench", "[.][!benchmark]")
{
constexpr uint32_t kNumBits = 4096;
uint64_t bits[kNumBits/64];
bx::MutableBitArrayView bs(bits, sizeof(bits) );
bx::RngMwc rng;
for (uint32_t ii = 0; ii < kNumBits; ii += 1 + rng.gen() % 12)
{
bs.set(ii, true);
}
bs.set(kNumBits - 256, kNumBits, false);
char name[64];
for (uint32_t numBits : { 4u, 12u, 40u, 200u, 300u })
{
uint32_t idx = 0;
bx::snprintf(name, sizeof(name), "find %u", numBits);
BENCHMARK(name)
{
idx = bs.find(numBits);
return idx;
};
REQUIRE( (bx::kInvalid == idx) == (bx::kInvalid == findRef(bs, 0, kNumBits, numBits) ) );
}
}