Error when running demo.py: No module named '_ext'

[lwoiceshyn]

Can you explain what this import is doing in path_nms.py?
from _ext import nms
It's preventing me from running the demo script. I'm using Python 3.6.

[ruotianluo]

Did you follow the fourth step of https://github.com/ruotianluo/pytorch-faster-rcnn#installation ?

[lwoiceshyn]

Yes, it seems to run fine, here is the output:

Including CUDA code. /home/leow/pytorch-faster-rcnn/lib/nms generating /tmp/tmpyk65xa34/_nms.c running build_ext building '_nms' extension creating home creating home/leow creating home/leow/pytorch-faster-rcnn creating home/leow/pytorch-faster-rcnn/lib creating home/leow/pytorch-faster-rcnn/lib/nms creating home/leow/pytorch-faster-rcnn/lib/nms/src gcc -pthread -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -DWITH_CUDA -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/THC -I/usr/local/cuda/include -I/home/leow/anaconda3/include/python3.6m -c _nms.c -o ./_nms.o gcc -pthread -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -DWITH_CUDA -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/THC -I/usr/local/cuda/include -I/home/leow/anaconda3/include/python3.6m -c /home/leow/pytorch-faster-rcnn/lib/nms/src/nms.c -o ./home/leow/pytorch-faster-rcnn/lib/nms/src/nms.o In file included from /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/TH.h:4:0, from /home/leow/pytorch-faster-rcnn/lib/nms/src/nms.c:1: /home/leow/pytorch-faster-rcnn/lib/nms/src/nms.c: In function ‘cpu_nms’: /home/leow/pytorch-faster-rcnn/lib/nms/src/nms.c:7:42: warning: passing argument 1 of ‘THLongTensor_isContiguous’ from incompatible pointer type [-Wincompatible-pointer-types] THArgCheck(THLongTensor_isContiguous(boxes), 2, "boxes must be contiguous"); ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THGeneral.h:78:35: note: in definition of macro ‘THArgCheck’ _THArgCheck(__FILE__, __LINE__, __VA_ARGS__); \ ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THTensor.h:8:39: note: expected ‘const THLongTensor * {aka const struct THLongTensor *}’ but argument is of type ‘THFloatTensor * {aka struct THFloatTensor *}’ #define THTensor_(NAME) TH_CONCAT_4(TH,Real,Tensor_,NAME) ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THGeneral.h:116:37: note: in definition of macro ‘TH_CONCAT_4_EXPAND’ #define TH_CONCAT_4_EXPAND(x,y,z,w) x ## y ## z ## w ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THTensor.h:8:27: note: in expansion of macro ‘TH_CONCAT_4’ #define THTensor_(NAME) TH_CONCAT_4(TH,Real,Tensor_,NAME) ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/generic/THTensor.h:115:12: note: in expansion of macro ‘THTensor_’ TH_API int THTensor_(isContiguous)(const THTensor *self); ^ /home/leow/pytorch-faster-rcnn/lib/nms/src/nms.c:9:42: warning: passing argument 1 of ‘THLongTensor_isContiguous’ from incompatible pointer type [-Wincompatible-pointer-types] THArgCheck(THLongTensor_isContiguous(areas), 4, "areas must be contiguous"); ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THGeneral.h:78:35: note: in definition of macro ‘THArgCheck’ _THArgCheck(__FILE__, __LINE__, __VA_ARGS__); \ ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THTensor.h:8:39: note: expected ‘const THLongTensor * {aka const struct THLongTensor *}’ but argument is of type ‘THFloatTensor * {aka struct THFloatTensor *}’ #define THTensor_(NAME) TH_CONCAT_4(TH,Real,Tensor_,NAME) ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THGeneral.h:116:37: note: in definition of macro ‘TH_CONCAT_4_EXPAND’ #define TH_CONCAT_4_EXPAND(x,y,z,w) x ## y ## z ## w ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/THTensor.h:8:27: note: in expansion of macro ‘TH_CONCAT_4’ #define THTensor_(NAME) TH_CONCAT_4(TH,Real,Tensor_,NAME) ^ /home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH/generic/THTensor.h:115:12: note: in expansion of macro ‘THTensor_’ TH_API int THTensor_(isContiguous)(const THTensor *self); ^ gcc -pthread -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -DWITH_CUDA -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/TH -I/home/leow/anaconda3/lib/python3.6/site-packages/torch/utils/ffi/../../lib/include/THC -I/usr/local/cuda/include -I/home/leow/anaconda3/include/python3.6m -c /home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.c -o ./home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.o /home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.c: In function ‘gpu_nms’: /home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.c:29:35: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types] unsigned long long* mask_flat = THCudaLongTensor_data(state, mask); ^ /home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.c:37:40: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types] unsigned long long * mask_cpu_flat = THLongTensor_data(mask_cpu); ^ /home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.c:40:39: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types] unsigned long long* remv_cpu_flat = THLongTensor_data(remv_cpu); ^ /home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.c:23:7: warning: unused variable ‘boxes_dim’ [-Wunused-variable] int boxes_dim = THCudaTensor_size(state, boxes, 1); ^ gcc -pthread -shared -L/home/leow/anaconda3/lib -Wl,-rpath=/home/leow/anaconda3/lib,--no-as-needed ./_nms.o ./home/leow/pytorch-faster-rcnn/lib/nms/src/nms.o ./home/leow/pytorch-faster-rcnn/lib/nms/src/nms_cuda.o /home/leow/pytorch-faster-rcnn/lib/nms/src/cuda/nms_kernel.cu.o -L/home/leow/anaconda3/lib -lpython3.6m -o ./_nms.so

[ruotianluo]

I guess it's because I'm running under python 2.7.

Try:
from ._ext import nms

build.py gives you _ext folder. So it should be the problem of importing.

[lwoiceshyn]

Yes, the directory imports are different in 3.6. That fix worked for the issue.

Thanks!