तेज गति से चलने या सिमड जानने के लिए

प्रकार की संख्या के साथ एक अनियंत्रित गिरफ्तारी सरणी है uint16_t। आपको अरे सरणी में v की घटनाओं की संख्या ज्ञात करने की आवश्यकता है।

int64_t cnt = 0; for (int i = 0; i < ARR_SIZE; ++i) if (arr[i] == v) ++cnt; 

 ------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------ BM_Count 2084 ns 2084 ns 333079 

पर्यावरण का परीक्षण करें

SIMD क्या है?

 #include <x86intrin.h> 

1. उदाहरण के लिए -mpopcnt , सभी आवश्यक -mpopcnt
2. आवश्यक विशेषता का समर्थन करने वाले प्रोसेसर के लक्ष्य आर्किटेक्चर को निर्दिष्ट करें, उदाहरण के लिए -march=corei7
3. कंपाइलर को प्रोसेसर के सभी एक्सटेंशन का उपयोग करने की क्षमता दें, जिस पर असेंबली होती है: -march=native

3 लाइनों के कोड में क्या त्वरित किया जा सकता है?

 for (int i = 0; i < ARR_SIZE; ++i) if (arr[i] == v) ++cnt; 

समानता के लिए ए और बी में पैक 16-बिट पूर्णांक की तुलना करें, और परिणामों को dst में संग्रहीत करें।

विकल्प 1

 int64_t cnt = 0; //     ""  8   auto sseVal = _mm_set1_epi16(VAL); for (int i = 0; i < ARR_SIZE; i += 8) { //     8       auto sseArr = _mm_set_epi16(arr[i + 7], arr[i + 6], arr[i + 5], arr[i + 4], arr[i + 3], arr[i + 2], arr[i + 1], arr[i]); //    * 2 cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); } //   2 cnt >>= 1; 

 ------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------ BM_Count 2084 ns 2084 ns 333079 BM_SSE_COUNT_SET_EPI 937 ns 937 ns 746435 

 ---------------  8   sseArr --------------- auto sseArr = _mm_set_epi16(arr[i + 7], arr[i + 6], arr[i + 5], arr[i + 4], arr[i + 3], arr[i + 2], 40133a: 48 8b 05 77 1d 20 00 mov 0x201d77(%rip),%rax # 6030b8 <_ZL3arr> arr[i + 1], arr[i]); 401341: 48 63 8d 9c fe ff ff movslq -0x164(%rbp),%rcx auto sseArr = _mm_set_epi16(arr[i + 7], arr[i + 6], arr[i + 5], arr[i + 4], arr[i + 3], arr[i + 2], 401348: 66 8b 54 48 0e mov 0xe(%rax,%rcx,2),%dx 40134d: 66 8b 74 48 0c mov 0xc(%rax,%rcx,2),%si 401352: 66 8b 7c 48 0a mov 0xa(%rax,%rcx,2),%di 401357: 66 44 8b 44 48 08 mov 0x8(%rax,%rcx,2),%r8w 40135d: 66 44 8b 4c 48 06 mov 0x6(%rax,%rcx,2),%r9w 401363: 66 44 8b 54 48 04 mov 0x4(%rax,%rcx,2),%r10w arr[i + 1], arr[i]); 401369: 66 44 8b 1c 48 mov (%rax,%rcx,2),%r11w 40136e: 66 8b 5c 48 02 mov 0x2(%rax,%rcx,2),%bx auto sseArr = _mm_set_epi16(arr[i + 7], arr[i + 6], arr[i + 5], arr[i + 4], arr[i + 3], arr[i + 2], 401373: 66 89 55 ce mov %dx,-0x32(%rbp) 401377: 66 89 75 cc mov %si,-0x34(%rbp) 40137b: 66 89 7d ca mov %di,-0x36(%rbp) 40137f: 66 44 89 45 c8 mov %r8w,-0x38(%rbp) 401384: 66 44 89 4d c6 mov %r9w,-0x3a(%rbp) 401389: 66 44 89 55 c4 mov %r10w,-0x3c(%rbp) 40138e: 66 89 5d c2 mov %bx,-0x3e(%rbp) 401392: 66 44 89 5d c0 mov %r11w,-0x40(%rbp) 401397: 44 0f b7 75 c0 movzwl -0x40(%rbp),%r14d 40139c: c4 c1 79 6e c6 vmovd %r14d,%xmm0 4013a1: 44 0f b7 75 c2 movzwl -0x3e(%rbp),%r14d 4013a6: c4 c1 79 c4 c6 01 vpinsrw $0x1,%r14d,%xmm0,%xmm0 4013ac: 44 0f b7 75 c4 movzwl -0x3c(%rbp),%r14d 4013b1: c4 c1 79 c4 c6 02 vpinsrw $0x2,%r14d,%xmm0,%xmm0 4013b7: 44 0f b7 75 c6 movzwl -0x3a(%rbp),%r14d 4013bc: c4 c1 79 c4 c6 03 vpinsrw $0x3,%r14d,%xmm0,%xmm0 4013c2: 44 0f b7 75 c8 movzwl -0x38(%rbp),%r14d 4013c7: c4 c1 79 c4 c6 04 vpinsrw $0x4,%r14d,%xmm0,%xmm0 4013cd: 44 0f b7 75 ca movzwl -0x36(%rbp),%r14d 4013d2: c4 c1 79 c4 c6 05 vpinsrw $0x5,%r14d,%xmm0,%xmm0 4013d8: 44 0f b7 75 cc movzwl -0x34(%rbp),%r14d 4013dd: c4 c1 79 c4 c6 06 vpinsrw $0x6,%r14d,%xmm0,%xmm0 4013e3: 44 0f b7 75 ce movzwl -0x32(%rbp),%r14d 4013e8: c4 c1 79 c4 c6 07 vpinsrw $0x7,%r14d,%xmm0,%xmm0 4013ee: c5 f9 7f 45 b0 vmovdqa %xmm0,-0x50(%rbp) 4013f3: c5 f9 6f 45 b0 vmovdqa -0x50(%rbp),%xmm0 4013f8: c5 f9 7f 85 80 fe ff vmovdqa %xmm0,-0x180(%rbp) 4013ff: ff ---------------    --------------- cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); 401400: c5 f9 6f 85 a0 fe ff vmovdqa -0x160(%rbp),%xmm0 401407: ff 401408: c5 f9 6f 8d 80 fe ff vmovdqa -0x180(%rbp),%xmm1 40140f: ff 401410: c5 f9 7f 45 a0 vmovdqa %xmm0,-0x60(%rbp) 401415: c5 f9 7f 4d 90 vmovdqa %xmm1,-0x70(%rbp) 40141a: c5 f9 6f 45 a0 vmovdqa -0x60(%rbp),%xmm0 40141f: c5 f9 6f 4d 90 vmovdqa -0x70(%rbp),%xmm1 401424: c5 f9 75 c1 vpcmpeqw %xmm1,%xmm0,%xmm0 401428: c5 f9 7f 45 80 vmovdqa %xmm0,-0x80(%rbp) 40142d: c5 f9 6f 45 80 vmovdqa -0x80(%rbp),%xmm0 401432: c5 79 d7 f0 vpmovmskb %xmm0,%r14d 401436: 44 89 b5 7c ff ff ff mov %r14d,-0x84(%rbp) 40143d: 44 8b b5 7c ff ff ff mov -0x84(%rbp),%r14d 401444: f3 45 0f b8 f6 popcnt %r14d,%r14d 401449: 49 63 c6 movslq %r14d,%rax 40144c: 48 03 85 b8 fe ff ff add -0x148(%rbp),%rax 401453: 48 89 85 b8 fe ff ff mov %rax,-0x148(%rbp) 

विकल्प 2

128-पूर्णांक डेटा के पूर्ण-बिट डेटा को अनलॉग्ड मेमोरी से dst में लोड करें

 int64_t cnt = 0; auto sseVal = _mm_set1_epi16(VAL); for (int i = 0; i < ARR_SIZE; i += 8) { auto sseArr = _mm_loadu_si128((__m128i *) &arr[i]); cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); } 

 ------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------ BM_Count 2084 ns 2084 ns 333079 BM_SSE_COUNT_SET_EPI 937 ns 937 ns 746435 BM_SSE_COUNT_LOADU 454 ns 454 ns 1548455 

  auto sseArr = _mm_loadu_si128((__m128i *) &arr[i]); 401695: 48 8b 05 1c 1a 20 00 mov 0x201a1c(%rip),%rax # 6030b8 <_ZL3arr> 40169c: 48 63 8d bc fe ff ff movslq -0x144(%rbp),%rcx 4016a3: 48 8d 04 48 lea (%rax,%rcx,2),%rax 4016a7: 48 89 45 d8 mov %rax,-0x28(%rbp) 4016ab: 48 8b 45 d8 mov -0x28(%rbp),%rax 4016af: c5 fa 6f 00 vmovdqu (%rax),%xmm0 4016b3: c5 f9 7f 85 a0 fe ff vmovdqa %xmm0,-0x160(%rbp) 4016ba: ff cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); 4016bb: c5 f9 6f 85 c0 fe ff vmovdqa -0x140(%rbp),%xmm0 4016c2: ff 4016c3: c5 f9 6f 8d a0 fe ff vmovdqa -0x160(%rbp),%xmm1 4016ca: ff 4016cb: c5 f9 7f 45 c0 vmovdqa %xmm0,-0x40(%rbp) 4016d0: c5 f9 7f 4d b0 vmovdqa %xmm1,-0x50(%rbp) 4016d5: c5 f9 6f 45 c0 vmovdqa -0x40(%rbp),%xmm0 4016da: c5 f9 6f 4d b0 vmovdqa -0x50(%rbp),%xmm1 4016df: c5 f9 75 c1 vpcmpeqw %xmm1,%xmm0,%xmm0 4016e3: c5 f9 7f 45 a0 vmovdqa %xmm0,-0x60(%rbp) 4016e8: c5 f9 6f 45 a0 vmovdqa -0x60(%rbp),%xmm0 4016ed: c5 f9 d7 d0 vpmovmskb %xmm0,%edx 4016f1: 89 55 9c mov %edx,-0x64(%rbp) 4016f4: 8b 55 9c mov -0x64(%rbp),%edx 4016f7: f3 0f b8 d2 popcnt %edx,%edx 4016fb: 48 63 c2 movslq %edx,%rax 4016fe: 48 03 85 d8 fe ff ff add -0x128(%rbp),%rax 401705: 48 89 85 d8 fe ff ff mov %rax,-0x128(%rbp) 

विकल्प 3

 int64_t cnt = 0; auto sseVal = _mm_set1_epi16(VAL); for (int i = 0; i < ARR_SIZE; i += 8) { auto sseArr = *(__m128i *) &allignedArr[i]; cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); } 

 ------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------ BM_Count 2084 ns 2084 ns 333079 BM_SSE_COUNT_SET_EPI 937 ns 937 ns 746435 BM_SSE_COUNT_LOADU 454 ns 454 ns 1548455 BM_SSE_COUNT_DIRECT 395 ns 395 ns 1770803 

  auto sseArr = *(__m128i *) &allignedArr[i]; 40193c: 48 8b 05 7d 17 20 00 mov 0x20177d(%rip),%rax # 6030c0 <_ZL11allignedArr> 401943: 48 63 8d cc fe ff ff movslq -0x134(%rbp),%rcx 40194a: c5 f9 6f 04 48 vmovdqa (%rax,%rcx,2),%xmm0 40194f: c5 f9 7f 85 b0 fe ff vmovdqa %xmm0,-0x150(%rbp) 401956: ff cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); 401957: c5 f9 6f 85 d0 fe ff vmovdqa -0x130(%rbp),%xmm0 40195e: ff 40195f: c5 f9 6f 8d b0 fe ff vmovdqa -0x150(%rbp),%xmm1 401966: ff 401967: c5 f9 7f 45 d0 vmovdqa %xmm0,-0x30(%rbp) 40196c: c5 f9 7f 4d c0 vmovdqa %xmm1,-0x40(%rbp) 401971: c5 f9 6f 45 d0 vmovdqa -0x30(%rbp),%xmm0 401976: c5 f9 6f 4d c0 vmovdqa -0x40(%rbp),%xmm1 40197b: c5 f9 75 c1 vpcmpeqw %xmm1,%xmm0,%xmm0 40197f: c5 f9 7f 45 b0 vmovdqa %xmm0,-0x50(%rbp) 401984: c5 f9 6f 45 b0 vmovdqa -0x50(%rbp),%xmm0 401989: c5 f9 d7 d0 vpmovmskb %xmm0,%edx 40198d: 89 55 ac mov %edx,-0x54(%rbp) 401990: 8b 55 ac mov -0x54(%rbp),%edx 401993: f3 0f b8 d2 popcnt %edx,%edx 401997: 48 63 c2 movslq %edx,%rax 40199a: 48 03 85 e8 fe ff ff add -0x118(%rbp),%rax 4019a1: 48 89 85 e8 fe ff ff mov %rax,-0x118(%rbp) 

निष्कर्ष

 ------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------ BM_Count 129 ns 129 ns 5359145 BM_SSE_COUNT_SET_EPI 70 ns 70 ns 9936200 BM_SSE_COUNT_LOADU 49 ns 49 ns 14187659 BM_SSE_COUNT_DIRECT 53 ns 53 ns 13401612 

 #include <benchmark/benchmark.h> #include <x86intrin.h> #include <cstring> #define ARR_SIZE 1024 #define VAL 50 static int16_t *getRandArr() { auto res = new int16_t[ARR_SIZE]; for (int i = 0; i < ARR_SIZE; ++i) { res[i] = static_cast<int16_t>(rand() % (VAL * 2)); } return res; } static auto arr = getRandArr(); static int16_t *getAllignedArr() { auto res = aligned_alloc(16, sizeof(int16_t) * ARR_SIZE); memcpy(res, arr, sizeof(int16_t) * ARR_SIZE); return static_cast<int16_t *>(res); } static auto allignedArr = getAllignedArr(); static void BM_Count(benchmark::State &state) { for (auto _ : state) { int64_t cnt = 0; for (int i = 0; i < ARR_SIZE; ++i) if (arr[i] == VAL) ++cnt; benchmark::DoNotOptimize(cnt); } } BENCHMARK(BM_Count); static void BM_SSE_COUNT_SET_EPI(benchmark::State &state) { for (auto _ : state) { int64_t cnt = 0; auto sseVal = _mm_set1_epi16(VAL); for (int i = 0; i < ARR_SIZE; i += 8) { auto sseArr = _mm_set_epi16(arr[i + 7], arr[i + 6], arr[i + 5], arr[i + 4], arr[i + 3], arr[i + 2], arr[i + 1], arr[i]); cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); } benchmark::DoNotOptimize(cnt >> 1); } } BENCHMARK(BM_SSE_COUNT_SET_EPI); static void BM_SSE_COUNT_LOADU(benchmark::State &state) { for (auto _ : state) { int64_t cnt = 0; auto sseVal = _mm_set1_epi16(VAL); for (int i = 0; i < ARR_SIZE; i += 8) { auto sseArr = _mm_loadu_si128((__m128i *) &arr[i]); cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); } benchmark::DoNotOptimize(cnt >> 1); } } BENCHMARK(BM_SSE_COUNT_LOADU); static void BM_SSE_COUNT_DIRECT(benchmark::State &state) { for (auto _ : state) { int64_t cnt = 0; auto sseVal = _mm_set1_epi16(VAL); for (int i = 0; i < ARR_SIZE; i += 8) { auto sseArr = *(__m128i *) &allignedArr[i]; cnt += _popcnt32(_mm_movemask_epi8(_mm_cmpeq_epi16(sseVal, sseArr))); } benchmark::DoNotOptimize(cnt >> 1); } } BENCHMARK(BM_SSE_COUNT_DIRECT); BENCHMARK_MAIN();