libcxx initial import
llvm-svn: 103490
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 3e519524c118651123eecf60c2bbc5d65ad9bac3
diff --git a/src/hash.cpp b/src/hash.cpp
new file mode 100644
index 0000000..a6bd311
--- /dev/null
+++ b/src/hash.cpp
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+//===-------------------------- hash.cpp ----------------------------------===//
+//
+// ÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊÊThe LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "__hash_table"
+#include "algorithm"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace {
+
+// handle all next_prime(i) for i in [1, 210), special case 0
+const unsigned small_primes[] =
+{
+ 0,
+ 2,
+ 3,
+ 5,
+ 7,
+ 11,
+ 13,
+ 17,
+ 19,
+ 23,
+ 29,
+ 31,
+ 37,
+ 41,
+ 43,
+ 47,
+ 53,
+ 59,
+ 61,
+ 67,
+ 71,
+ 73,
+ 79,
+ 83,
+ 89,
+ 97,
+ 101,
+ 103,
+ 107,
+ 109,
+ 113,
+ 127,
+ 131,
+ 137,
+ 139,
+ 149,
+ 151,
+ 157,
+ 163,
+ 167,
+ 173,
+ 179,
+ 181,
+ 191,
+ 193,
+ 197,
+ 199,
+ 211
+};
+
+// potential primes = 210*k + indices[i], k >= 1
+// these numbers are not divisible by 2, 3, 5 or 7
+// (or any integer 2 <= j <= 10 for that matter).
+const unsigned indices[] =
+{
+ 1,
+ 11,
+ 13,
+ 17,
+ 19,
+ 23,
+ 29,
+ 31,
+ 37,
+ 41,
+ 43,
+ 47,
+ 53,
+ 59,
+ 61,
+ 67,
+ 71,
+ 73,
+ 79,
+ 83,
+ 89,
+ 97,
+ 101,
+ 103,
+ 107,
+ 109,
+ 113,
+ 121,
+ 127,
+ 131,
+ 137,
+ 139,
+ 143,
+ 149,
+ 151,
+ 157,
+ 163,
+ 167,
+ 169,
+ 173,
+ 179,
+ 181,
+ 187,
+ 191,
+ 193,
+ 197,
+ 199,
+ 209
+};
+
+}
+
+// Returns: If n == 0, returns 0. Else returns the lowest prime number that
+// is greater than or equal to n.
+//
+// The algorithm creates a list of small primes, plus an open-ended list of
+// potential primes. All prime numbers are potential prime numbers. However
+// some potential prime numbers are not prime. In an ideal world, all potential
+// prime numbers would be prime. Candiate prime numbers are chosen as the next
+// highest potential prime. Then this number is tested for prime by dividing it
+// by all potential prime numbers less than the sqrt of the candidate.
+//
+// This implementation defines potential primes as those numbers not divisible
+// by 2, 3, 5, and 7. Other (common) implementations define potential primes
+// as those not divisible by 2. A few other implementations define potential
+// primes as those not divisible by 2 or 3. By raising the number of small
+// primes which the potential prime is not divisible by, the set of potential
+// primes more closely approximates the set of prime numbers. And thus there
+// are fewer potential primes to search, and fewer potential primes to divide
+// against.
+
+size_t
+__next_prime(size_t n)
+{
+ const size_t L = 210;
+ const size_t N = sizeof(small_primes) / sizeof(small_primes[0]);
+ // If n is small enough, search in small_primes
+ if (n <= small_primes[N-1])
+ return *std::lower_bound(small_primes, small_primes + N, n);
+ // Else n > largest small_primes
+ // Start searching list of potential primes: L * k0 + indices[in]
+ const size_t M = sizeof(indices) / sizeof(indices[0]);
+ // Select first potential prime >= n
+ // Known a-priori n >= L
+ size_t k0 = n / L;
+ size_t in = std::lower_bound(indices, indices + M, n % L) - indices;
+ n = L * k0 + indices[in];
+ while (true)
+ {
+ // Divide n by all primes or potential primes (i) until:
+ // 1. The division is even, so try next potential prime.
+ // 2. The i > sqrt(n), in which case n is prime.
+ // It is known a-priori that n is not divisible by 2, 3, 5 or 7,
+ // so don't test those (j == 5 -> divide by 11 first). And the
+ // potential primes start with 211, so don't test against the last
+ // small prime.
+ for (size_t j = 5; j < N - 1; ++j)
+ {
+ if (n % small_primes[j] == 0)
+ goto next;
+ if (n / small_primes[j] < small_primes[j])
+ return n;
+ }
+ // n wasn't divisible by small primes, try potential primes
+ {
+ size_t i = 211;
+ while (true)
+ {
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 10;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 8;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 8;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 6;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 4;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 2;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ i += 10;
+ if (n % i == 0)
+ break;
+ if (n / i < i)
+ return n;
+
+ // This will loop i to the next "plane" of potential primes
+ i += 2;
+ }
+ }
+next:
+ // n is not prime. Increment n to next potential prime.
+ if (++in == M)
+ {
+ ++k0;
+ in = 0;
+ }
+ n = L * k0 + indices[in];
+ }
+}
+
+_LIBCPP_END_NAMESPACE_STD