Restructuring C++ project: (#3146)

Summary:
* Reduce unnecessary header inclusions in models and io.

* Move autocast to separate folder and hide autograd implementation in an anonymous namespace.

* Moving files in subfolders.

Reviewed By: fmassa

Differential Revision: D25461523

fbshipit-source-id: 756eeb6848aacaa474de4825ed4c1045d17e2cea

torchvision/csrc/cpu/image/readjpeg_cpu.cpp → torchvision/csrc/io/image/cpu/readjpeg_cpu.cpp

 #include "readjpeg_cpu.h"
 
-#include <ATen/ATen.h>
-
 #if !JPEG_FOUND
 torch::Tensor decodeJPEG(const torch::Tensor& data, ImageReadMode mode) {
   TORCH_CHECK(
       false, "decodeJPEG: torchvision not compiled with libjpeg support");
 }
 #else
-#include <jpeglib.h>
-#include <setjmp.h>
-#include "jpegcommon.h"
+#include "../jpegcommon.h"
 
 struct torch_jpeg_mgr {
   struct jpeg_source_mgr pub;

torchvision/csrc/cpu/image/readjpeg_cpu.h → torchvision/csrc/io/image/cpu/readjpeg_cpu.h

 #pragma once
 
-#include <torch/torch.h>
-#include "image_read_mode.h"
+#include <torch/types.h>
+#include "../image_read_mode.h"
 
 C10_EXPORT torch::Tensor decodeJPEG(
     const torch::Tensor& data,

torchvision/csrc/cpu/image/readpng_cpu.cpp → torchvision/csrc/io/image/cpu/readpng_cpu.cpp

 #include "readpng_cpu.h"
 
-#include <ATen/ATen.h>
-
 #if !PNG_FOUND
 torch::Tensor decodePNG(const torch::Tensor& data, ImageReadMode mode) {
   TORCH_CHECK(false, "decodePNG: torchvision not compiled with libPNG support");

torchvision/csrc/cpu/image/readpng_cpu.h → torchvision/csrc/io/image/cpu/readpng_cpu.h

 #pragma once
 
-#include <torch/torch.h>
-#include "image_read_mode.h"
+#include <torch/types.h>
+#include "../image_read_mode.h"
 
 C10_EXPORT torch::Tensor decodePNG(
     const torch::Tensor& data,

torchvision/csrc/cpu/image/writejpeg_cpu.cpp → torchvision/csrc/io/image/cpu/writejpeg_cpu.cpp

 #include "writejpeg_cpu.h"
 
-#include <setjmp.h>
-#include <string>
-
 #if !JPEG_FOUND
 
 torch::Tensor encodeJPEG(const torch::Tensor& data, int64_t quality) {
@@ -11,9 +8,7 @@ torch::Tensor encodeJPEG(const torch::Tensor& data, int64_t quality) {
 }
 
 #else
-
-#include <jpeglib.h>
-#include "jpegcommon.h"
+#include "../jpegcommon.h"
 
 torch::Tensor encodeJPEG(const torch::Tensor& data, int64_t quality) {
   // Define compression structures and error handling

torchvision/csrc/cpu/image/writejpeg_cpu.h → torchvision/csrc/io/image/cpu/writejpeg_cpu.h

 #pragma once
 
-#include <torch/torch.h>
+#include <torch/types.h>
 
 C10_EXPORT torch::Tensor encodeJPEG(const torch::Tensor& data, int64_t quality);

torchvision/csrc/cpu/image/writepng_cpu.cpp → torchvision/csrc/io/image/cpu/writepng_cpu.cpp

 #include "writejpeg_cpu.h"
 
-#include <setjmp.h>
-#include <string>
-
 #if !PNG_FOUND
 
 torch::Tensor encodePNG(const torch::Tensor& data, int64_t compression_level) {
@@ -10,8 +7,8 @@ torch::Tensor encodePNG(const torch::Tensor& data, int64_t compression_level) {
 }
 
 #else
-
 #include <png.h>
+#include <setjmp.h>
 
 struct torch_mem_encode {
   char* buffer;

torchvision/csrc/cpu/image/writepng_cpu.h → torchvision/csrc/io/image/cpu/writepng_cpu.h

 #pragma once
 
-#include <torch/torch.h>
+#include <torch/types.h>
 
 C10_EXPORT torch::Tensor encodePNG(
     const torch::Tensor& data,

torchvision/csrc/cpu/image/image.cpp → torchvision/csrc/io/image/image.cpp

-
 #include "image.h"
-#include <ATen/ATen.h>
+
 #include <Python.h>
 
 // If we are in a Windows environment, we need to define

torchvision/csrc/io/image/image.h

+#pragma once
+
+#include "cpu/read_image_cpu.h"
+#include "cpu/read_write_file_cpu.h"
+#include "cpu/readjpeg_cpu.h"
+#include "cpu/readpng_cpu.h"
+#include "cpu/writejpeg_cpu.h"
+#include "cpu/writepng_cpu.h"

torchvision/csrc/cpu/image/jpegcommon.cpp → torchvision/csrc/io/image/jpegcommon.cpp

+#if JPEG_FOUND
 #include "jpegcommon.h"
-#include <string>
 
-#if JPEG_FOUND
 void torch_jpeg_error_exit(j_common_ptr cinfo) {
   /* cinfo->err really points to a torch_jpeg_error_mgr struct, so coerce
    * pointer */

torchvision/csrc/cpu/image/jpegcommon.h → torchvision/csrc/io/image/jpegcommon.h

@@ -8,7 +8,6 @@
 #if JPEG_FOUND
 #include <jpeglib.h>
 #include <setjmp.h>
-#include <string>
 
 static const JOCTET EOI_BUFFER[1] = {JPEG_EOI};
 struct torch_jpeg_error_mgr {

torchvision/csrc/models/alexnet.h

 #pragma once
 
-#include <torch/torch.h>
+#include <torch/nn.h>
 #include "../macros.h"
 
 namespace vision {

torchvision/csrc/models/densenet.h

 #pragma once
 
-#include <torch/torch.h>
+#include <torch/nn.h>
 #include "../macros.h"
 
 namespace vision {