unittests/ADT/HashingTest.cpp

   1 //===- llvm/unittest/ADT/HashingTest.cpp ----------------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Hashing.h unit tests.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "gtest/gtest.h"
  15 #include "llvm/ADT/Hashing.h"
  16 #include "llvm/Support/DataTypes.h"
  17 #include <deque>
  18 #include <list>
  19 #include <map>
  20 #include <vector>
  21
  22 namespace llvm {
  23
  24 // Helper for test code to print hash codes.
  25 void PrintTo(const hash_code &code, std::ostream *os) {
  26   *os << static_cast<size_t>(code);
  27 }
  28
  29 // Fake an object that is recognized as hashable data to test super large
  30 // objects.
  31 struct LargeTestInteger { uint64_t arr[8]; };
  32
  33 namespace hashing {
  34 namespace detail {
  35 template <> struct is_hashable_data<LargeTestInteger> : true_type {};
  36 } // namespace detail
  37 } // namespace hashing
  38
  39 } // namespace llvm
  40
  41 using namespace llvm;
  42
  43 namespace {
  44
  45 struct NonPOD {
  46   uint64_t x, y;
  47   NonPOD(uint64_t x, uint64_t y) : x(x), y(y) {}
  48   ~NonPOD() {}
  49   friend hash_code hash_value(const NonPOD &obj) {
  50     return hash_combine(obj.x, obj.y);
  51   }
  52 };
  53
  54
  55 TEST(HashingTest, HashValueBasicTest) {
  56   int x = 42, y = 43, c = 'x';
  57   void *p = 0;
  58   uint64_t i = 71;
  59   const unsigned ci = 71;
  60   volatile int vi = 71;
  61   const volatile int cvi = 71;
  62   uintptr_t addr = reinterpret_cast<uintptr_t>(&y);
  63   EXPECT_EQ(hash_value(42), hash_value(x));
  64   EXPECT_NE(hash_value(42), hash_value(y));
  65   EXPECT_NE(hash_value(42), hash_value(p));
  66   EXPECT_EQ(hash_value(71), hash_value(i));
  67   EXPECT_EQ(hash_value(71), hash_value(ci));
  68   EXPECT_EQ(hash_value(71), hash_value(vi));
  69   EXPECT_EQ(hash_value(71), hash_value(cvi));
  70   EXPECT_EQ(hash_value(c), hash_value('x'));
  71   EXPECT_EQ(hash_value('4'), hash_value('0' + 4));
  72   EXPECT_EQ(hash_value(addr), hash_value(&y));
  73
  74   EXPECT_EQ(hash_combine(42, 43), hash_value(std::make_pair(42, 43)));
  75   EXPECT_NE(hash_combine(43, 42), hash_value(std::make_pair(42, 43)));
  76   EXPECT_NE(hash_combine(42, 43), hash_value(std::make_pair(42ull, 43ull)));
  77   EXPECT_NE(hash_combine(42, 43), hash_value(std::make_pair(42, 43ull)));
  78   EXPECT_NE(hash_combine(42, 43), hash_value(std::make_pair(42ull, 43)));
  79
  80   // Note that pairs are implicitly flattened to a direct sequence of data and
  81   // hashed efficiently as a consequence.
  82   EXPECT_EQ(hash_combine(42, 43, 44),
  83             hash_value(std::make_pair(42, std::make_pair(43, 44))));
  84   EXPECT_EQ(hash_value(std::make_pair(42, std::make_pair(43, 44))),
  85             hash_value(std::make_pair(std::make_pair(42, 43), 44)));
  86
  87   // Ensure that pairs which have padding bytes *inside* them don't get treated
  88   // this way.
  89   EXPECT_EQ(hash_combine('0', hash_combine(1ull, '2')),
  90             hash_value(std::make_pair('0', std::make_pair(1ull, '2'))));
  91
  92   // Ensure that non-POD pairs don't explode the traits used.
  93   NonPOD obj1(1, 2), obj2(3, 4), obj3(5, 6);
  94   EXPECT_EQ(hash_combine(obj1, hash_combine(obj2, obj3)),
  95             hash_value(std::make_pair(obj1, std::make_pair(obj2, obj3))));
  96 }
  97
  98 template <typename T, size_t N> T *begin(T (&arr)[N]) { return arr; }
  99 template <typename T, size_t N> T *end(T (&arr)[N]) { return arr + N; }
 100
 101 // Provide a dummy, hashable type designed for easy verification: its hash is
 102 // the same as its value.
 103 struct HashableDummy { size_t value; };
 104 hash_code hash_value(HashableDummy dummy) { return dummy.value; }
 105
 106 TEST(HashingTest, HashCombineRangeBasicTest) {
 107   // Leave this uninitialized in the hope that valgrind will catch bad reads.
 108   int dummy;
 109   hash_code dummy_hash = hash_combine_range(&dummy, &dummy);
 110   EXPECT_NE(hash_code(0), dummy_hash);
 111
 112   const int arr1[] = { 1, 2, 3 };
 113   hash_code arr1_hash = hash_combine_range(begin(arr1), end(arr1));
 114   EXPECT_NE(dummy_hash, arr1_hash);
 115   EXPECT_EQ(arr1_hash, hash_combine_range(begin(arr1), end(arr1)));
 116
 117   const std::vector<int> vec(begin(arr1), end(arr1));
 118   EXPECT_EQ(arr1_hash, hash_combine_range(vec.begin(), vec.end()));
 119
 120   const std::list<int> list(begin(arr1), end(arr1));
 121   EXPECT_EQ(arr1_hash, hash_combine_range(list.begin(), list.end()));
 122
 123   const std::deque<int> deque(begin(arr1), end(arr1));
 124   EXPECT_EQ(arr1_hash, hash_combine_range(deque.begin(), deque.end()));
 125
 126   const int arr2[] = { 3, 2, 1 };
 127   hash_code arr2_hash = hash_combine_range(begin(arr2), end(arr2));
 128   EXPECT_NE(dummy_hash, arr2_hash);
 129   EXPECT_NE(arr1_hash, arr2_hash);
 130
 131   const int arr3[] = { 1, 1, 2, 3 };
 132   hash_code arr3_hash = hash_combine_range(begin(arr3), end(arr3));
 133   EXPECT_NE(dummy_hash, arr3_hash);
 134   EXPECT_NE(arr1_hash, arr3_hash);
 135
 136   const int arr4[] = { 1, 2, 3, 3 };
 137   hash_code arr4_hash = hash_combine_range(begin(arr4), end(arr4));
 138   EXPECT_NE(dummy_hash, arr4_hash);
 139   EXPECT_NE(arr1_hash, arr4_hash);
 140
 141   const size_t arr5[] = { 1, 2, 3 };
 142   const HashableDummy d_arr5[] = { {1}, {2}, {3} };
 143   hash_code arr5_hash = hash_combine_range(begin(arr5), end(arr5));
 144   hash_code d_arr5_hash = hash_combine_range(begin(d_arr5), end(d_arr5));
 145   EXPECT_EQ(arr5_hash, d_arr5_hash);
 146 }
 147
 148 TEST(HashingTest, HashCombineRangeLengthDiff) {
 149   // Test that as only the length varies, we compute different hash codes for
 150   // sequences.
 151   std::map<size_t, size_t> code_to_size;
 152   std::vector<char> all_one_c(256, '\xff');
 153   for (unsigned Idx = 1, Size = all_one_c.size(); Idx < Size; ++Idx) {
 154     hash_code code = hash_combine_range(&all_one_c[0], &all_one_c[0] + Idx);
 155     std::map<size_t, size_t>::iterator
 156       I = code_to_size.insert(std::make_pair(code, Idx)).first;
 157     EXPECT_EQ(Idx, I->second);
 158   }
 159   code_to_size.clear();
 160   std::vector<char> all_zero_c(256, '\0');
 161   for (unsigned Idx = 1, Size = all_zero_c.size(); Idx < Size; ++Idx) {
 162     hash_code code = hash_combine_range(&all_zero_c[0], &all_zero_c[0] + Idx);
 163     std::map<size_t, size_t>::iterator
 164       I = code_to_size.insert(std::make_pair(code, Idx)).first;
 165     EXPECT_EQ(Idx, I->second);
 166   }
 167   code_to_size.clear();
 168   std::vector<unsigned> all_one_int(512, -1);
 169   for (unsigned Idx = 1, Size = all_one_int.size(); Idx < Size; ++Idx) {
 170     hash_code code = hash_combine_range(&all_one_int[0], &all_one_int[0] + Idx);
 171     std::map<size_t, size_t>::iterator
 172       I = code_to_size.insert(std::make_pair(code, Idx)).first;
 173     EXPECT_EQ(Idx, I->second);
 174   }
 175   code_to_size.clear();
 176   std::vector<unsigned> all_zero_int(512, 0);
 177   for (unsigned Idx = 1, Size = all_zero_int.size(); Idx < Size; ++Idx) {
 178     hash_code code = hash_combine_range(&all_zero_int[0], &all_zero_int[0] + Idx);
 179     std::map<size_t, size_t>::iterator
 180       I = code_to_size.insert(std::make_pair(code, Idx)).first;
 181     EXPECT_EQ(Idx, I->second);
 182   }
 183 }
 184
 185 TEST(HashingTest, HashCombineRangeGoldenTest) {
 186   struct { const char *s; uint64_t hash; } golden_data[] = {
 187 #if SIZE_MAX == UINT64_MAX
 188     { "a",                                0xaeb6f9d5517c61f8ULL },
 189     { "ab",                               0x7ab1edb96be496b4ULL },
 190     { "abc",                              0xe38e60bf19c71a3fULL },
 191     { "abcde",                            0xd24461a66de97f6eULL },
 192     { "abcdefgh",                         0x4ef872ec411dec9dULL },
 193     { "abcdefghijklm",                    0xe8a865539f4eadfeULL },
 194     { "abcdefghijklmnopqrstu",            0x261cdf85faaf4e79ULL },
 195     { "abcdefghijklmnopqrstuvwxyzabcdef", 0x43ba70e4198e3b2aULL },
 196     { "abcdefghijklmnopqrstuvwxyzabcdef"
 197       "abcdefghijklmnopqrstuvwxyzghijkl"
 198       "abcdefghijklmnopqrstuvwxyzmnopqr"
 199       "abcdefghijklmnopqrstuvwxyzstuvwx"
 200       "abcdefghijklmnopqrstuvwxyzyzabcd", 0xdcd57fb2afdf72beULL },
 201     { "a",                                0xaeb6f9d5517c61f8ULL },
 202     { "aa",                               0xf2b3b69a9736a1ebULL },
 203     { "aaa",                              0xf752eb6f07b1cafeULL },
 204     { "aaaaa",                            0x812bd21e1236954cULL },
 205     { "aaaaaaaa",                         0xff07a2cff08ac587ULL },
 206     { "aaaaaaaaaaaaa",                    0x84ac949d54d704ecULL },
 207     { "aaaaaaaaaaaaaaaaaaaaa",            0xcb2c8fb6be8f5648ULL },
 208     { "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", 0xcc40ab7f164091b6ULL },
 209     { "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 210       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 211       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 212       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 213       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", 0xc58e174c1e78ffe9ULL },
 214     { "z",                                0x1ba160d7e8f8785cULL },
 215     { "zz",                               0x2c5c03172f1285d7ULL },
 216     { "zzz",                              0x9d2c4f4b507a2ac3ULL },
 217     { "zzzzz",                            0x0f03b9031735693aULL },
 218     { "zzzzzzzz",                         0xe674147c8582c08eULL },
 219     { "zzzzzzzzzzzzz",                    0x3162d9fa6938db83ULL },
 220     { "zzzzzzzzzzzzzzzzzzzzz",            0x37b9a549e013620cULL },
 221     { "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz", 0x8921470aff885016ULL },
 222     { "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 223       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 224       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 225       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 226       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz", 0xf60fdcd9beb08441ULL },
 227     { "a",                                0xaeb6f9d5517c61f8ULL },
 228     { "ab",                               0x7ab1edb96be496b4ULL },
 229     { "aba",                              0x3edb049950884d0aULL },
 230     { "ababa",                            0x8f2de9e73a97714bULL },
 231     { "abababab",                         0xee14a29ddf0ce54cULL },
 232     { "ababababababa",                    0x38b3ddaada2d52b4ULL },
 233     { "ababababababababababa",            0xd3665364219f2b85ULL },
 234     { "abababababababababababababababab", 0xa75cd6afbf1bc972ULL },
 235     { "abababababababababababababababab"
 236       "abababababababababababababababab"
 237       "abababababababababababababababab"
 238       "abababababababababababababababab"
 239       "abababababababababababababababab", 0x840192d129f7a22bULL }
 240 #elif SIZE_MAX == UINT32_MAX
 241     { "a",                                0x000000004605f745ULL },
 242     { "ab",                               0x00000000d5f06301ULL },
 243     { "abc",                              0x00000000559fe1eeULL },
 244     { "abcde",                            0x00000000424028d7ULL },
 245     { "abcdefgh",                         0x000000007bb119f8ULL },
 246     { "abcdefghijklm",                    0x00000000edbca513ULL },
 247     { "abcdefghijklmnopqrstu",            0x000000007c15712eULL },
 248     { "abcdefghijklmnopqrstuvwxyzabcdef", 0x000000000b3aad66ULL },
 249     { "abcdefghijklmnopqrstuvwxyzabcdef"
 250       "abcdefghijklmnopqrstuvwxyzghijkl"
 251       "abcdefghijklmnopqrstuvwxyzmnopqr"
 252       "abcdefghijklmnopqrstuvwxyzstuvwx"
 253       "abcdefghijklmnopqrstuvwxyzyzabcd", 0x000000008c758c8bULL },
 254     { "a",                                0x000000004605f745ULL },
 255     { "aa",                               0x00000000dc0a52daULL },
 256     { "aaa",                              0x00000000b309274fULL },
 257     { "aaaaa",                            0x00000000203b5ef6ULL },
 258     { "aaaaaaaa",                         0x00000000a429e18fULL },
 259     { "aaaaaaaaaaaaa",                    0x000000008662070bULL },
 260     { "aaaaaaaaaaaaaaaaaaaaa",            0x000000003f11151cULL },
 261     { "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", 0x000000008600fe20ULL },
 262     { "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 263       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 264       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 265       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
 266       "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", 0x000000004e0e0804ULL },
 267     { "z",                                0x00000000c5e405e9ULL },
 268     { "zz",                               0x00000000a8d8a2c6ULL },
 269     { "zzz",                              0x00000000fc2af672ULL },
 270     { "zzzzz",                            0x0000000047d9efe6ULL },
 271     { "zzzzzzzz",                         0x0000000080d77794ULL },
 272     { "zzzzzzzzzzzzz",                    0x00000000405f93adULL },
 273     { "zzzzzzzzzzzzzzzzzzzzz",            0x00000000fc72838dULL },
 274     { "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz", 0x000000007ce160f1ULL },
 275     { "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 276       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 277       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 278       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz"
 279       "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz", 0x00000000aed9ed1bULL },
 280     { "a",                                0x000000004605f745ULL },
 281     { "ab",                               0x00000000d5f06301ULL },
 282     { "aba",                              0x00000000a85cd91bULL },
 283     { "ababa",                            0x000000009e3bb52eULL },
 284     { "abababab",                         0x000000002709b3b9ULL },
 285     { "ababababababa",                    0x000000003a234174ULL },
 286     { "ababababababababababa",            0x000000005c63e5ceULL },
 287     { "abababababababababababababababab", 0x0000000013f74334ULL },
 288     { "abababababababababababababababab"
 289       "abababababababababababababababab"
 290       "abababababababababababababababab"
 291       "abababababababababababababababab"
 292       "abababababababababababababababab", 0x00000000c1a6f135ULL },
 293 #else
 294 #error This test only supports 64-bit and 32-bit systems.
 295 #endif
 296   };
 297   for (unsigned i = 0; i < sizeof(golden_data)/sizeof(*golden_data); ++i) {
 298     StringRef str = golden_data[i].s;
 299     hash_code hash = hash_combine_range(str.begin(), str.end());
 300 #if 0 // Enable this to generate paste-able text for the above structure.
 301     std::string member_str = "\"" + str.str() + "\",";
 302     fprintf(stderr, " { %-35s 0x%016llxULL },\n",
 303             member_str.c_str(), static_cast<uint64_t>(hash));
 304 #endif
 305     EXPECT_EQ(static_cast<size_t>(golden_data[i].hash),
 306               static_cast<size_t>(hash));
 307   }
 308 }
 309
 310 TEST(HashingTest, HashCombineBasicTest) {
 311   // Hashing a sequence of homogenous types matches range hashing.
 312   const int i1 = 42, i2 = 43, i3 = 123, i4 = 999, i5 = 0, i6 = 79;
 313   const int arr1[] = { i1, i2, i3, i4, i5, i6 };
 314   EXPECT_EQ(hash_combine_range(arr1, arr1 + 1), hash_combine(i1));
 315   EXPECT_EQ(hash_combine_range(arr1, arr1 + 2), hash_combine(i1, i2));
 316   EXPECT_EQ(hash_combine_range(arr1, arr1 + 3), hash_combine(i1, i2, i3));
 317   EXPECT_EQ(hash_combine_range(arr1, arr1 + 4), hash_combine(i1, i2, i3, i4));
 318   EXPECT_EQ(hash_combine_range(arr1, arr1 + 5),
 319             hash_combine(i1, i2, i3, i4, i5));
 320   EXPECT_EQ(hash_combine_range(arr1, arr1 + 6),
 321             hash_combine(i1, i2, i3, i4, i5, i6));
 322
 323   // Hashing a sequence of heterogenous types which *happen* to all produce the
 324   // same data for hashing produces the same as a range-based hash of the
 325   // fundamental values.
 326   const size_t s1 = 1024, s2 = 8888, s3 = 9000000;
 327   const HashableDummy d1 = { 1024 }, d2 = { 8888 }, d3 = { 9000000 };
 328   const size_t arr2[] = { s1, s2, s3 };
 329   EXPECT_EQ(hash_combine_range(begin(arr2), end(arr2)),
 330             hash_combine(s1, s2, s3));
 331   EXPECT_EQ(hash_combine(s1, s2, s3), hash_combine(s1, s2, d3));
 332   EXPECT_EQ(hash_combine(s1, s2, s3), hash_combine(s1, d2, s3));
 333   EXPECT_EQ(hash_combine(s1, s2, s3), hash_combine(d1, s2, s3));
 334   EXPECT_EQ(hash_combine(s1, s2, s3), hash_combine(d1, d2, s3));
 335   EXPECT_EQ(hash_combine(s1, s2, s3), hash_combine(d1, d2, d3));
 336
 337   // Permuting values causes hashes to change.
 338   EXPECT_NE(hash_combine(i1, i1, i1), hash_combine(i1, i1, i2));
 339   EXPECT_NE(hash_combine(i1, i1, i1), hash_combine(i1, i2, i1));
 340   EXPECT_NE(hash_combine(i1, i1, i1), hash_combine(i2, i1, i1));
 341   EXPECT_NE(hash_combine(i1, i1, i1), hash_combine(i2, i2, i1));
 342   EXPECT_NE(hash_combine(i1, i1, i1), hash_combine(i2, i2, i2));
 343   EXPECT_NE(hash_combine(i2, i1, i1), hash_combine(i1, i1, i2));
 344   EXPECT_NE(hash_combine(i1, i1, i2), hash_combine(i1, i2, i1));
 345   EXPECT_NE(hash_combine(i1, i2, i1), hash_combine(i2, i1, i1));
 346
 347   // Changing type w/o changing value causes hashes to change.
 348   EXPECT_NE(hash_combine(i1, i2, i3), hash_combine((char)i1, i2, i3));
 349   EXPECT_NE(hash_combine(i1, i2, i3), hash_combine(i1, (char)i2, i3));
 350   EXPECT_NE(hash_combine(i1, i2, i3), hash_combine(i1, i2, (char)i3));
 351
 352   // This is array of uint64, but it should have the exact same byte pattern as
 353   // an array of LargeTestIntegers.
 354   const uint64_t bigarr[] = {
 355     0xaaaaaaaaababababULL, 0xacacacacbcbcbcbcULL, 0xccddeeffeeddccbbULL,
 356     0xdeadbeafdeadbeefULL, 0xfefefefededededeULL, 0xafafafafededededULL,
 357     0xffffeeeeddddccccULL, 0xaaaacbcbffffababULL,
 358     0xaaaaaaaaababababULL, 0xacacacacbcbcbcbcULL, 0xccddeeffeeddccbbULL,
 359     0xdeadbeafdeadbeefULL, 0xfefefefededededeULL, 0xafafafafededededULL,
 360     0xffffeeeeddddccccULL, 0xaaaacbcbffffababULL,
 361     0xaaaaaaaaababababULL, 0xacacacacbcbcbcbcULL, 0xccddeeffeeddccbbULL,
 362     0xdeadbeafdeadbeefULL, 0xfefefefededededeULL, 0xafafafafededededULL,
 363     0xffffeeeeddddccccULL, 0xaaaacbcbffffababULL
 364   };
 365   // Hash a preposterously large integer, both aligned with the buffer and
 366   // misaligned.
 367   const LargeTestInteger li = { {
 368     0xaaaaaaaaababababULL, 0xacacacacbcbcbcbcULL, 0xccddeeffeeddccbbULL,
 369     0xdeadbeafdeadbeefULL, 0xfefefefededededeULL, 0xafafafafededededULL,
 370     0xffffeeeeddddccccULL, 0xaaaacbcbffffababULL
 371   } };
 372   // Rotate the storage from 'li'.
 373   const LargeTestInteger l2 = { {
 374     0xacacacacbcbcbcbcULL, 0xccddeeffeeddccbbULL, 0xdeadbeafdeadbeefULL,
 375     0xfefefefededededeULL, 0xafafafafededededULL, 0xffffeeeeddddccccULL,
 376     0xaaaacbcbffffababULL, 0xaaaaaaaaababababULL
 377   } };
 378   const LargeTestInteger l3 = { {
 379     0xccddeeffeeddccbbULL, 0xdeadbeafdeadbeefULL, 0xfefefefededededeULL,
 380     0xafafafafededededULL, 0xffffeeeeddddccccULL, 0xaaaacbcbffffababULL,
 381     0xaaaaaaaaababababULL, 0xacacacacbcbcbcbcULL
 382   } };
 383   EXPECT_EQ(hash_combine_range(begin(bigarr), end(bigarr)),
 384             hash_combine(li, li, li));
 385   EXPECT_EQ(hash_combine_range(bigarr, bigarr + 9),
 386             hash_combine(bigarr[0], l2));
 387   EXPECT_EQ(hash_combine_range(bigarr, bigarr + 10),
 388             hash_combine(bigarr[0], bigarr[1], l3));
 389   EXPECT_EQ(hash_combine_range(bigarr, bigarr + 17),
 390             hash_combine(li, bigarr[0], l2));
 391   EXPECT_EQ(hash_combine_range(bigarr, bigarr + 18),
 392             hash_combine(li, bigarr[0], bigarr[1], l3));
 393   EXPECT_EQ(hash_combine_range(bigarr, bigarr + 18),
 394             hash_combine(bigarr[0], l2, bigarr[9], l3));
 395   EXPECT_EQ(hash_combine_range(bigarr, bigarr + 20),
 396             hash_combine(bigarr[0], l2, bigarr[9], l3, bigarr[18], bigarr[19]));
 397 }
 398
 399 }