szha commented on issue #18938:
URL:
https://github.com/apache/incubator-mxnet/issues/18938#issuecomment-678068013
So here's the problem:
```
% DMLC_LOG_STACK_TRACE_DEPTH=150 MXNET_ENGINE_TYPE=NaiveEngine lldb
python3.7 -- test_18938.py
(lldb) target create "python3.7"
Current executable set to 'python3.7' (x86_64).
(lldb) settings set -- target.run-args "test_18938.py"
(lldb) run
Process 45668 launched: '/usr/local/bin/python3.7' (x86_64)
Process 45668 stopped
* thread #2, stop reason = exec
frame #0: 0x0000000100006000 dyld`_dyld_start
dyld`_dyld_start:
-> 0x100006000 <+0>: popq %rdi
0x100006001 <+1>: pushq $0x0
0x100006003 <+3>: movq %rsp, %rbp
0x100006006 <+6>: andq $-0x10, %rsp
(lldb) cont
Process 45668 resuming
[23:29:59] ../src/engine/engine.cc:55: MXNet start using engine: NaiveEngine
Process 45668 stopped
* thread #2, queue = 'com.apple.main-thread', stop reason = EXC_ARITHMETIC
(code=EXC_I386_DIV, subcode=0x0)
frame #0: 0x0000000115e85453
libmxnet.dylib`mxnet::op::SequenceLastOp<mshadow::cpu, float,
int>::Forward(this=0x000000010066a490, ctx=0x00007ffeefbfc2b0,
in_data=0x00000001006dcf08, req=0x00007ffeefbfc310,
out_data=0x00000001006dcf50, aux_args=0x00000001006dcf38) at
sequence_last-inl.h:158
155
156 auto batch = (axis != 0) ? d0 : d1;
157 auto max_seq_len = in_data[seq_last::kData].size(axis);
-> 158 auto rest_size = dsize / (d0 * d1);
159
160 Tensor<xpu, 3, DType> data =
161 in_data[seq_last::kData].get_with_shape<xpu, 3, DType>(
```
https://github.com/apache/incubator-mxnet/blob/9bdd4d6347c284770ee5bfe5ae98f1dabc283829/src/operator/sequence_last-inl.h#L158
The code needs to guard against zero-size array for right operand of `/`,
and we should add a smoke test to guard against such problem in this op,
similar to https://github.com/apache/incubator-mxnet/pull/18972/files
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