[XLA:GPU] Remove IsForwardCycle and IsBackwardCycle as they are not u…

…sed.

PiperOrigin-RevId: 719420695

xla/service/collective_ops_utils.cc

@@ -803,38 +803,6 @@ bool IsSyncCollective(const HloInstruction* instr) {
 using SourceTargetPair = std::pair<int64_t, int64_t>;
 using SourceTargetPairs = std::vector<SourceTargetPair>;
 
-bool IsForwardCycle(const SourceTargetPairs& pairs) {
-  int64_t size = pairs.size();
-  if (size <= 1) return false;  // self reference is not a cycle.
-  const SourceTargetPair& last_pair = pairs[size - 1];
-  if (last_pair.first != size - 1 || last_pair.second != 0) {
-    return false;
-  }
-  for (int64_t i = 0; i < size - 1; ++i) {
-    const SourceTargetPair& pair = pairs[i];
-    if (pair.first != i || pair.second != i + 1) {
-      return false;
-    }
-  }
-  return true;
-}
-
-bool IsBackwardCycle(const SourceTargetPairs& pairs) {
-  int64_t size = pairs.size();
-  if (size <= 1) return false;  // self reference is not a cycle.
-  const SourceTargetPair& first_pair = pairs[0];
-  if (first_pair.first != 0 || first_pair.second != size - 1) {
-    return false;
-  }
-  for (int64_t i = 1; i < size; ++i) {
-    const SourceTargetPair& pair = pairs[i];
-    if (pair.first != i || pair.second != i - 1) {
-      return false;
-    }
-  }
-  return true;
-}
-
 std::pair<CycleType, std::set<int>> GetCycleTypeAndIndices(
     const SourceTargetPairs& pairs) {
   std::set<int> seen_replica_ids;

xla/service/collective_ops_utils.h

@@ -251,16 +251,6 @@ HloInstruction* IsOrHasCollectiveWithChannelId(HloInstruction* instruction);
 // Returns true if instruction is a synchronous collective op.
 bool IsSyncCollective(const HloInstruction* instr);
 
-// Returns true if the (a, b) pairs form a forward cycle with all participants
-// in the cycle, such as {{0,1},{1,2},{2,3},{3,0}}. We assume that the (a, b)
-// pairs are ordered as they are generated by SPMD partitioning.
-bool IsForwardCycle(const std::vector<std::pair<int64_t, int64_t>>& pairs);
-
-// Returns true if the (a, b) pairs form a backward cycle with all participants
-// in the cycle, such as {{0,3},{1,0},{2,1},{3,2}}. We assume that the (a, b)
-// pairs are ordered as they are generated by SPMD partitioning.
-bool IsBackwardCycle(const std::vector<std::pair<int64_t, int64_t>>& pairs);
-
 // Returns the cycle type and indices of the vertices that form cycles. For
 // example, GetCycleTypeAndIndices({{0,3},{1,0},{2,1},{3,2}}) returns
 // {kBackward, {0}}, since the communication pattern contains a backward cycle

xla/service/collective_ops_utils_test.cc

@@ -149,37 +149,6 @@ TEST(CollectiveOpsUtilsTest, CollectiveWithChannelId2) {
   EXPECT_EQ(IsOrHasCollectiveWithChannelId(fusion2.get()), nullptr);
 }
 
-TEST(CollectiveOpsUtilsTest, IsForwardCycle) {
-  EXPECT_TRUE(IsForwardCycle({{0, 1}, {1, 0}}));
-  EXPECT_TRUE(IsForwardCycle({{0, 1}, {1, 2}, {2, 3}, {3, 0}}));
-  EXPECT_FALSE(IsForwardCycle({{0, 0}})) << "Self link is not a cycle!";
-  EXPECT_FALSE(IsForwardCycle({{}})) << "Self link due to initialization to 0";
-
-  EXPECT_FALSE(IsForwardCycle({}));
-  EXPECT_FALSE(IsForwardCycle({{0, 1}}));
-  EXPECT_FALSE(IsForwardCycle({{0, 1}, {2, 0}})) << "No link between 1 and 2";
-  EXPECT_FALSE(IsForwardCycle({{1, 0}, {0, 1}})) << "Backward cycle";
-  EXPECT_FALSE(IsForwardCycle({{3, 0}, {0, 1}, {1, 2}, {2, 3}}))
-      << "Unordered pairs are not a cycle";
-  EXPECT_FALSE(IsForwardCycle({{0, 1}, {1, 2}, {2, 3}, {4, 5}, {3, 0}}))
-      << "Out of order pairs are not a cycle";
-}
-
-TEST(CollectiveOpsUtilsTest, IsBackwardCycle) {
-  EXPECT_TRUE(IsBackwardCycle({{0, 1}, {1, 0}}));
-  EXPECT_TRUE(IsBackwardCycle({{0, 3}, {1, 0}, {2, 1}, {3, 2}}));
-  EXPECT_FALSE(IsBackwardCycle({{0, 0}})) << "Self link is a backward cycle!";
-  EXPECT_FALSE(IsBackwardCycle({{}})) << "Self link due to initialization to 0";
-
-  EXPECT_FALSE(IsForwardCycle({}));
-  EXPECT_FALSE(IsForwardCycle({{1, 0}}));
-  EXPECT_FALSE(IsForwardCycle({{2, 1}, {0, 2}})) << "No link between 1 and 2";
-  EXPECT_FALSE(IsBackwardCycle({{3, 2}, {0, 3}, {1, 0}, {2, 1}}))
-      << "Unordered pairs are not a cycle";
-  EXPECT_FALSE(IsForwardCycle({{0, 1}, {1, 2}, {4, 5}, {3, 0}}))
-      << "Out of order pairs are not a cycle";
-}
-
 TEST(CollectiveOpsUtilsTest, GetForwardCycleIndices) {
   auto res_one_cycle = GetCycleTypeAndIndices({{0, 1}, {1, 2}, {2, 3}, {3, 0}});
   EXPECT_EQ(res_one_cycle.first, CycleType::kForward);