simplify random code

ortools/base/random.cc

@@ -11,24 +11,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#if defined(__GNUC__)
-#include <unistd.h>
-#if defined(__linux__)
-#include <linux/limits.h>
-#endif
-#endif
-#if defined(_MSC_VER)
-#include <Winsock2.h>
-#include <windows.h>
-#define PATH_MAX 4096
-#else
-#include <sys/time.h>
-#endif
 
 #include <cstring>
 #include <ctime>
+#include <random>
 
-#include "ortools/base/hash.h"
 #include "ortools/base/random.h"
 
 namespace operations_research {
@@ -47,47 +34,8 @@ uint64_t ACMRandom::operator()(uint64_t val_max) {
   return val_max == 0 ? 0 : Next64() % val_max;
 }
 
-namespace {
-static inline uint32_t Word32At(const char* ptr) {
-  return ((static_cast<uint32_t>(ptr[0])) +
-          (static_cast<uint32_t>(ptr[1]) << 8) +
-          (static_cast<uint32_t>(ptr[2]) << 16) +
-          (static_cast<uint32_t>(ptr[3]) << 24));
-}
-}  // namespace
-
 int32_t ACMRandom::HostnamePidTimeSeed() {
-  char name[PATH_MAX + 20];  // need 12 bytes for 3 'empty' uint32_t's
-  assert(sizeof(name) - PATH_MAX > sizeof(uint32_t) * 3);
-
-  if (gethostname(name, PATH_MAX) != 0) {
-    strcpy(name, "default-hostname");  // NOLINT
-  }
-  const int namelen = strlen(name);
-  for (size_t i = 0; i < sizeof(uint32_t) * 3; ++i) {
-    name[namelen + i] = '\0';  // so we mix 0's once we get to end-of-string
-  }
-#if defined(__GNUC__)
-  uint32_t a = getpid();
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  uint32_t b = static_cast<uint32_t>((tv.tv_sec + tv.tv_usec) & 0xffffffff);
-#elif defined(_MSC_VER)
-  uint32_t a = GetCurrentProcessId();
-  uint32_t b = GetTickCount();
-#else  // Do not know what to do, returning 0.
-  return 0;
-#endif
-  uint32_t c = 0;
-  for (int i = 0; i < namelen; i += sizeof(uint32_t) * 3) {
-    a += Word32At(name + i);
-    b += Word32At(name + i + sizeof(uint32_t));
-    c += Word32At(name + i + sizeof(uint32_t) + sizeof(uint32_t));
-    mix(a, b, c);
-  }
-  c += namelen;  // one final mix
-  mix(a, b, c);
-  return static_cast<int32_t>(c);  // I guess the seed can be negative
+  return std::random_device{}();
 }
 
 int32_t ACMRandom::DeterministicSeed() { return 0; }

ortools/base/random.h

@@ -59,8 +59,6 @@ class MTRandom : public ACMRandom {
   explicit MTRandom(const std::string& str_seed)
       : ACMRandom(GenerateInt32SeedFromString(str_seed)) {}
 
-  MTRandom() : ACMRandom(ACMRandom::HostnamePidTimeSeed()) {}
-
  private:
   int32_t GenerateInt32SeedFromString(const std::string& str) {
     uint32_t seed = 1234567;

ortools/sat/simplification.cc

@@ -23,7 +23,6 @@
 #include "ortools/algorithms/dynamic_partition.h"
 #include "ortools/base/adjustable_priority_queue-inl.h"
 #include "ortools/base/logging.h"
-#include "ortools/base/random.h"
 #include "ortools/base/stl_util.h"
 #include "ortools/base/strong_vector.h"
 #include "ortools/base/timer.h"