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Precompute the divisor to ensure that no kind of compiler would process it on the fly at each call.

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This commit is contained in:
Pierre-Emmanuel Viel 2020-07-01 18:52:05 +02:00
parent a84afb6334
commit 327f92cc46
1 changed files with 9 additions and 2 deletions
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11
modules/flann/include/opencv2/flann/dist.h
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@ -506,7 +506,7 @@ struct Hamming2
const uint64_t* pa = reinterpret_cast<const uint64_t*>(a); const uint64_t* pa = reinterpret_cast<const uint64_t*>(a);
const uint64_t* pb = reinterpret_cast<const uint64_t*>(b); const uint64_t* pb = reinterpret_cast<const uint64_t*>(b);
ResultType result = 0; ResultType result = 0;
size /= (sizeof(uint64_t)/sizeof(unsigned char)); size /= long_word_size_;
for(size_t i = 0; i < size; ++i ) { for(size_t i = 0; i < size; ++i ) {
result += popcnt64(*pa ^ *pb); result += popcnt64(*pa ^ *pb);
++pa; ++pa;
@ -516,7 +516,7 @@ struct Hamming2
const uint32_t* pa = reinterpret_cast<const uint32_t*>(a); const uint32_t* pa = reinterpret_cast<const uint32_t*>(a);
const uint32_t* pb = reinterpret_cast<const uint32_t*>(b); const uint32_t* pb = reinterpret_cast<const uint32_t*>(b);
ResultType result = 0; ResultType result = 0;
size /= (sizeof(uint32_t)/sizeof(unsigned char)); size /= long_word_size_;
for(size_t i = 0; i < size; ++i ) { for(size_t i = 0; i < size; ++i ) {
result += popcnt32(*pa ^ *pb); result += popcnt32(*pa ^ *pb);
++pa; ++pa;
@ -525,6 +525,13 @@ struct Hamming2
#endif #endif
return result; return result;
} }
private:
#ifdef FLANN_PLATFORM_64_BIT
static const size_t long_word_size_ = sizeof(uint64_t)/sizeof(unsigned char);
#else
static const size_t long_word_size_ = sizeof(uint32_t)/sizeof(unsigned char);
#endif
}; };