ComputeAtMap build failure `No potential concrete_id's found for disjoint set`

[jjsjann123]

Repro c++ script.

TEST_F(NVFuserTest, Repro) {
  auto fusion = std::make_unique<Fusion>();
  FusionGuard fg(fusion.get());

  TensorView* tv0 = makeContigConcreteTensor({1, 10});
  TensorView* tv1 = makeContigConcreteTensor({4, 10});
  TensorView* tv2 = relu(tv0);
  TensorView* tv3 = neg(tv0);
  TensorView* tv4 = add(tv2, tv3);
  TensorView* tv5 = cat({tv4, tv1}, /*dim=*/0);
  TensorView* tv6 = add(tv5, tv0);

  fusion->addInput(tv0);
  fusion->addInput(tv1);
  fusion->addOutput(tv6);

  auto options = at::TensorOptions().dtype(at::kFloat).device(at::kCUDA, 0); 
  at::Tensor t0 = at::randn({1, 10}, options);
  at::Tensor t1 = at::randn({4, 10}, options);
  std::vector<c10::IValue> aten_inputs = {t0, t1};

  FusionExecutorCache fec(std::move(fusion));
  auto out_tensors = fec.runFusionWithInputs(aten_inputs);

  testValidate(fec.fusion(), out_tensors, aten_inputs, __LINE__, __FILE__);
}

hits an assert vvv

C++ exception with description "!maybe_concrete_ids.vector().empty() INTERNAL ASSERT FAILED at "/opt/pytorch/nvfuser/csrc/compute_at_map.cpp":1111, please report a bug with repro script to NVFuser at https://github.com/NVIDIA/Fuser/issues. No potential concrete_id's found for disjoint set { bS0{1}; bS4{1}; bS6{1}; bS8{1}; bS10{1}rf; iS14{( ( 0 + 1 ) + 4 )}rf; iS11{5}rf; iS16{5}; iS18{5} }
Exception raised from computeConcreteId at /opt/pytorch/nvfuser/csrc/compute_at_map.cpp:1111 (most recent call first):

Full trace:

#0  0x00007fffb9c824a1 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc++.so.6
#1  0x0000555555ac7b9e in nvfuser::nvfCheckFail (func=0x555556d22ce6 "computeConcreteId", 
    file=0x555556d21e90 "/opt/pytorch/nvfuser/csrc/compute_at_map.cpp", line=1111, 
    msg="!maybe_concrete_ids.vector().empty() INTERNAL ASSERT FAILED at \"/opt/pytorch/nvfuser/csrc/compute_at_map.cpp\":1111, please report a bug with repro script to NVFuser at https://github.com/NVIDIA/Fuser/"...)
    at /opt/pytorch/nvfuser/csrc/exceptions.cpp:274
#2  0x0000555555ac7db3 in nvfuser::nvfErrorFail (func=0x555556d22ce6 "computeConcreteId", 
    file=0x555556d21e90 "/opt/pytorch/nvfuser/csrc/compute_at_map.cpp", line=1111, 
    condMsg=0x555556d22f28 "!maybe_concrete_ids.vector().empty() INTERNAL ASSERT FAILED at \"/opt/pytorch/nvfuser/csrc/compute_at_map.cpp\":1111, please report a bug with repro script to NVFuser at https://github.com/NVIDIA/Fuser/"..., 
    userMsg="No potential concrete_id's found for disjoint set { bS0{1}; bS4{1}; bS6{1}; bS8{1}; bS10{1}rf; iS14{( ( 0 + 1 ) + 4 )}rf; iS11{5}rf; iS16{5}; iS18{5} }") at /opt/pytorch/nvfuser/csrc/exceptions.cpp:300
#3  0x0000555555799b62 in nvfuser::ComputeAtMap::computeConcreteId (this=0x7fffffffb720, id=0x7fff21816100, 
    mode=nvfuser::IdMappingMode::PERMISSIVE) at /opt/pytorch/nvfuser/csrc/compute_at_map.cpp:1111
#4  0x000055555579a3b9 in nvfuser::ComputeAtMap::buildConcreteIds (this=0x7fffffffb720)
    at /opt/pytorch/nvfuser/csrc/compute_at_map.cpp:1179
#5  0x0000555555797ec2 in nvfuser::ComputeAtMap::build (this=0x7fffffffb720, fusion=0x7fff2106f380)
    at /opt/pytorch/nvfuser/csrc/compute_at_map.cpp:780
#6  0x0000555555797df7 in nvfuser::ComputeAtMap::ComputeAtMap (this=0x7fffffffb720, fusion=0x7fff2106f380, 
    allow_self_mapping=false) at /opt/pytorch/nvfuser/csrc/compute_at_map.cpp:775
#7  0x00005555560c877e in nvfuser::pointwise_utils::DomainMap::DomainMap (this=0x7fffffffb710, fusion=0x7fff2106f380)
    at /opt/pytorch/nvfuser/csrc/scheduler/pointwise_utils.cpp:113
#8  0x00005555560beb57 in nvfuser::(anonymous namespace)::DomainMap::DomainMap (this=0x7fffffffb710)
    at /opt/pytorch/nvfuser/csrc/scheduler/pointwise.cpp:121
#9  0x00005555560bebc0 in nvfuser::getReferenceTensorView (fusion=0x7fff2106f380)
    at /opt/pytorch/nvfuser/csrc/scheduler/pointwise.cpp:525
#10 0x00005555560bec74 in nvfuser::hasReferenceTensorView (fusion=0x7fff2106f380)
    at /opt/pytorch/nvfuser/csrc/scheduler/pointwise.cpp:531
#11 0x00005555560bbbd3 in nvfuser::PointWiseScheduler::canScheduleCompileTime (fusion=0x7fff2106f380)
    at /opt/pytorch/nvfuser/csrc/scheduler/pointwise.cpp:38
#12 0x00005555560ef1ab in nvfuser::(anonymous namespace)::checkCanSchedule<nvfuser::PointWiseScheduler> (fusion=0x7fff2106f380, 
    runtime_info=..., data_cache=0x0) at /opt/pytorch/nvfuser/csrc/scheduler/registry.cpp:190
#13 0x00005555560ed7ac in nvfuser::SchedulerEntry::canSchedule (sh=nvfuser::ScheduleHeuristic::PointWise, fusion=0x7fff2106f380, 
    runtime_info=..., data_cache=0x0) at /opt/pytorch/nvfuser/csrc/scheduler/registry.cpp:210
#14 0x00005555560edcfe in nvfuser::SchedulerEntry::proposeHeuristics (fusion=0x7fff2106f380, runtime_info=...)
    at /opt/pytorch/nvfuser/csrc/scheduler/registry.cpp:299
#15 0x0000555555c0505e in nvfuser::SegmentCandidateFinder::segment (fusion=std::unique_ptr<nvfuser::Fusion> = {...}, 
    inputs=0x7fffffffcde0, runtime_info=...) at /opt/pytorch/nvfuser/csrc/fusion_segmenter.cpp:1987
#16 0x0000555555e92968 in nvfuser::FusionKernelRuntime::FusionKernelRuntime (this=0x7fff218e40c0, 
    fusion=std::unique_ptr<nvfuser::Fusion> = {...}, args=..., serde_buffer=0x0, 
    forced_index_type=std::optional<nvfuser::PrimDataType> [no contained value], fusion_id=0, concrete_id=1, runtime_id=0, 
    auto_schedule=true) at /opt/pytorch/nvfuser/csrc/kernel_cache.cpp:1061
#17 0x0000555555ea30b5 in std::make_unique<nvfuser::FusionKernelRuntime, std::unique_ptr<nvfuser::Fusion, std::default_delete<nvfuser::Fusion> >, nvfuser::KernelArgumentHolder const&, decltype(nullptr), std::optional<nvfuser::PrimDataType>&, long&, long&, unsigned long, bool const&>(std::unique_ptr<nvfuser::Fusion, std::default_delete<nvfuser::Fusion> >&&, nvfuser::KernelArgumentHolder const&, decltype(nullptr)&&, std::optional<nvfuser::PrimDataType>&, long&, long&, unsigned long&&, bool const&) ()
    at /usr/include/c++/11/bits/unique_ptr.h:962
#18 0x0000555555e91115 in nvfuser::FusionExecutorCache::getKernelRuntimeFor (this=0x7fffffffd3c0, args=..., 
    forced_index_type=std::optional<nvfuser::PrimDataType> [no contained value]) at /opt/pytorch/nvfuser/csrc/kernel_cache.cpp:833
#19 0x0000555555e8f393 in nvfuser::FusionExecutorCache::runFusionWithInputs (this=0x7fffffffd3c0, inputs=..., 
    forced_index_type=std::optional<nvfuser::PrimDataType> [no contained value], 
    selected_device=std::optional<signed char> [no contained value]) at /opt/pytorch/nvfuser/csrc/kernel_cache.cpp:547

[jjsjann123]

In the example above:

(gdb) print id->fusion()->printMath(0)
Inputs:
  T0_g[ bS0{1}, iS1{10} ], float
  T1_g[ iS2{4}, iS3{10} ], float
Outputs:
  T8_g[ iS18{5}, iS19{10} ], float

%kernel_math {
Resize: bS10{1}rf by 0 and 4 -> iS11{5}rf
i21 = 0 + 1;
i30 = i21 + 4;
i37 = i21 + 4;
Resize: iS13{4}rf by ( 0 + 1 ) and 0 -> iS14{( ( 0 + 1 ) + 4 )}rf
T2_l[ bS4{1}, iS5{10} ]
   = relu(T0_g[ bS0{1}, iS1{10} ]);
T3_l[ bS6{1}, iS7{10} ]
   = -T0_g[ bS0{1}, iS1{10} ];
T4_l[ bS8{1}, iS9{10} ]
   = T2_l[ bS4{1}, iS5{10} ]
   + T3_l[ bS6{1}, iS7{10} ];
T5_l[ iS11{5}rf, iS12{10} ]
   = pad( T4_l[ bS8{1}, iS9{10} ], {0, 4, 0, 0} )
T6_l[ iS14{( ( 0 + 1 ) + 4 )}rf, iS15{10} ]
   = pad( T1_g[ iS2{4}, iS3{10} ], {i21, 0, 0, 0} )
T7_l[ iS16{5}, iS17{10} ]
   = cat( T5_l[ iS11{5}rf, iS12{10} ], T6_l[ iS14{( ( 0 + 1 ) + 4 )}rf, iS15{10} ], 0 )
T8_g[ iS18{5}, iS19{10} ]
   = T7_l[ iS16{5}, iS17{10} ]
   + T0_g[ bS0{1}, iS1{10} ];
b50 = blockIdx.x >= 0;
b52 = gridDim.x > 0;
b54 = blockIdx.x < gridDim.x;
b56 = blockIdx.y >= 0;
b58 = gridDim.y > 0;
b60 = blockIdx.y < gridDim.y;
b62 = blockIdx.z >= 0;
b64 = gridDim.z > 0;
b66 = blockIdx.z < gridDim.z;
b68 = threadIdx.x >= 0;
b70 = blockDim.x > 0;
b72 = threadIdx.x < blockDim.x;
b74 = threadIdx.y >= 0;
b76 = blockDim.y > 0;
b78 = threadIdx.y < blockDim.y;
b80 = threadIdx.z >= 0;
b82 = blockDim.z > 0;
b84 = threadIdx.z < blockDim.z;
s86 = getMetaData(T0_g[ bS0{1}, iS1{10} ])
s87 = getMetaData(T1_g[ iS2{4}, iS3{10} ])
}

No potential concrete_id's found for disjoint set { bS0{1}; bS4{1}; bS6{1}; bS8{1}; bS10{1}rf; iS14{( ( 0 + 1 ) + 4 )}rf; iS11{5}rf; iS16{5}; iS18{5} }")

Looks like after the last swap we ended up with an empty maybe_concrete_ids somehow.