Update to latest libprimesieve

kimwalisch · Sep 17, 2023 · 30beeab · 30beeab
1 parent 4397959
commit 30beeab
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Showing 2 changed files with 18 additions and 30 deletions.
diff --git a/lib/primesieve/doc/CPP_API.md b/lib/primesieve/doc/CPP_API.md
@@ -459,31 +459,25 @@ int main()
   primesieve::iterator it;
   it.generate_next_primes();
 
-  uint64_t sum = 0;
   uint64_t limit = 10000000000;
+  __m512i sums = _mm512_setzero_si512();
 
   while (it.primes_[it.size_ - 1] <= limit)
   {
-    std::size_t i = 0;
-    __m512i vsums = _mm512_setzero_si512();
-
     // Sum 64-bit primes using AVX512
-    for (; i + 8 < it.size_; i += 8) {
-      __m512i primes = _mm512_loadu_si512((__m512i*) &it.primes_[i]);
-      vsums = _mm512_add_epi64(vsums, primes);
+    for (std::size_t i = 0; i < it.size_; i += 8) {
+      __mmask8 mask = (i + 8 < it.size_) ? 0xff : 0xff >> (i + 8 - it.size_);
+      __m512i primes = _mm512_maskz_loadu_epi64(mask, (__m512i*) &it.primes_[i]);
+      sums = _mm512_add_epi64(sums, primes);
     }
 
-    // Sum 8 integers in the vsums vector
-    sum += _mm512_reduce_add_epi64(vsums);
-
-    // Process the remaining primes (at most 7)
-    for (; i < it.size_; i++)
-      sum += it.primes_[i];
-
     // Generate up to 2^10 new primes
     it.generate_next_primes();
   }
 
+  // Sum the 8 partial sums
+  uint64_t sum = _mm512_reduce_add_epi64(sums);
+
   // Process the remaining primes (at most 2^10)
   for (std::size_t i = 0; it.primes_[i] <= limit; i++)
     sum += it.primes_[i];
@@ -499,7 +493,7 @@ int main()
 
 ```bash
 # Unix-like OSes
-c++ -O3 -mavx512f primesum.cpp -o primesum -lprimesieve
+c++ -O3 -mavx512f -funroll-loops primesum.cpp -o primesum -lprimesieve
 time ./primesum
 ```
 

diff --git a/lib/primesieve/doc/C_API.md b/lib/primesieve/doc/C_API.md
@@ -525,31 +525,25 @@ int main(void)
   primesieve_init(&it);
   primesieve_generate_next_primes(&it);
 
-  uint64_t sum = 0;
   uint64_t limit = 10000000000;
+  __m512i sums = _mm512_setzero_si512();
 
   while (it.primes[it.size - 1] <= limit)
   {
-    size_t i = 0;
-    __m512i vsums = _mm512_setzero_si512();
-
     // Sum 64-bit primes using AVX512
-    for (; i + 8 < it.size; i += 8) {
-      __m512i primes = _mm512_loadu_si512((__m512i*) &it.primes[i]);
-      vsums = _mm512_add_epi64(vsums, primes);
+    for (size_t i = 0; i < it.size; i += 8) {
+      __mmask8 mask = (i + 8 < it.size) ? 0xff : 0xff >> (i + 8 - it.size);
+      __m512i primes = _mm512_maskz_loadu_epi64(mask, (__m512i*) &it.primes[i]);
+      sums = _mm512_add_epi64(sums, primes);
     }
 
-    // Sum 8 integers in the vsums vector
-    sum += _mm512_reduce_add_epi64(vsums);
-
-    // Process the remaining primes (at most 7)
-    for (; i < it.size; i++)
-      sum += it.primes[i];
-
     // Generate up to 2^10 new primes
     primesieve_generate_next_primes(&it);
   }
 
+  // Sum the 8 partial sums
+  uint64_t sum = _mm512_reduce_add_epi64(sums);
+
   // Process the remaining primes (at most 2^10)
   for (size_t i = 0; it.primes[i] <= limit; i++)
     sum += it.primes[i];
@@ -566,7 +560,7 @@ int main(void)
 
 ```bash
 # Unix-like OSes
-cc -O3 -mavx512f primesum.c -o primesum -lprimesieve
+cc -O3 -mavx512f -funroll-loops primesum.c -o primesum -lprimesieve
 time ./primesum
 ```