iblis17 opened a new issue #9050: got segfault from lenet with stn example URL: https://github.com/apache/incubator-mxnet/issues/9050 Hi, We encounter segfault with stn. Here is the original issue https://github.com/dmlc/MXNet.jl/issues/369. TL;DR: Segfault happened in CPU-version `mshadow::BilinearSamplingBackward` gdb trace here: ```julia Thread 37 "julia" received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7fff35a15700 (LWP 13819)] 0x00007fff83e77ba0 in mshadow::BilinearSamplingBackward<float> (input_grad=..., grid_src_data=..., output_grad=..., input_data=...) at src/operator/spatial_transformer.cc:120 120 *(g_input + data_index + 1) += *(grad + grad_index) * top_left_y_w (gdb) bt #0 0x00007fff83e77ba0 in mshadow::BilinearSamplingBackward<float> (input_grad=..., grid_src_data=..., output_grad=..., input_data=...) at src/operator/spatial_transformer.cc:120 #1 0x00007fff83e5f18c in mxnet::op::SpatialTransformerOp<mshadow::cpu, float>::Backward (this=0x38bcd30, ctx=..., out_grad=std::vector of length 1, capacity 1 = {...}, in_data=std::vector of length 2, capacity 2 = {...}, out_data=std::vector of length 3, capacity 3 = {...}, req=std::vector of length 2, capacity 2 = {...}, in_grad=std::vector of length 2, capacity 2 = {...}, aux_args=std::vector of length 0, capacity 0) at src/operator/./spatial_transformer-inl.h:136 (gdb) p grad $1 = (const float *) 0x7fff251e6f90 (gdb) p top_left_y_w $2 = 0.376614928 (gdb) p grad_index $3 = 0 (gdb) p *(grad + grad_index) $4 = 0.00177509966 (gdb) p g_input + data_index + 1 $5 = (float *) 0x80032442cf50 (gdb) p g_input $6 = (float *) 0x7fff2442cf50 (gdb) p data_index $7 = 4294967295 ``` actually `data_index` become a negative number. Also, segfault can reproduce in Python's example (with 1.0 prebuilt binary) (https://github.com/dmlc/MXNet.jl/issues/369#issuecomment-350617043) ``` ./train_mnist.py --network lenet --add_stn --optimizer adam ```
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