Clarify that libtorch API is C++17 compatible (pytorch#136471)

As it relies on some common C++17 primitives, such as `std::optional`
Replace all docs references from C++14 to C++17

Fixes pytorch#133205

Pull Request resolved: pytorch#136471
Approved by: https://github.com/kit1980, https://github.com/atalman

Author: malfet

RELEASE.md

@@ -48,16 +48,16 @@
 
 Following is the Release Compatibility Matrix for PyTorch releases:
 
-| PyTorch version | Python | Stable CUDA | Experimental CUDA | Stable ROCm |
-| --- | --- | --- | --- | --- |
-| 2.5 | >=3.9, <=3.12, (3.13 experimental) | CUDA 11.8, CUDA 12.1, CUDA 12.4, CUDNN 9.1.0.70  | None | ROCm 6.2 |
-| 2.4 | >=3.8, <=3.12 | CUDA 11.8, CUDA 12.1, CUDNN 9.1.0.70  | CUDA 12.4, CUDNN 9.1.0.70 | ROCm 6.1 |
-| 2.3 | >=3.8, <=3.11, (3.12 experimental) | CUDA 11.8, CUDNN 8.7.0.84 | CUDA 12.1, CUDNN 8.9.2.26 | ROCm 6.0 |
-| 2.2 | >=3.8, <=3.11, (3.12 experimental) | CUDA 11.8, CUDNN 8.7.0.84 | CUDA 12.1, CUDNN 8.9.2.26 | ROCm 5.7 |
-| 2.1 | >=3.8, <=3.11 | CUDA 11.8, CUDNN 8.7.0.84 | CUDA 12.1, CUDNN 8.9.2.26 | ROCm 5.6 |
-| 2.0 | >=3.8, <=3.11 | CUDA 11.7, CUDNN 8.5.0.96 | CUDA 11.8, CUDNN 8.7.0.84 | ROCm 5.4 |
-| 1.13 | >=3.7, <=3.10 | CUDA 11.6, CUDNN 8.3.2.44 | CUDA 11.7, CUDNN 8.5.0.96 | ROCm 5.2 |
-| 1.12 | >=3.7, <=3.10 | CUDA 11.3, CUDNN 8.3.2.44 | CUDA 11.6, CUDNN 8.3.2.44 | ROCm 5.0 |
+| PyTorch version | Python | C++ | Stable CUDA | Experimental CUDA | Stable ROCm |
+| --- | --- | --- | --- | --- | --- |
+| 2.5 | >=3.9, <=3.12, (3.13 experimental) | C++17 | CUDA 11.8, CUDA 12.1, CUDA 12.4, CUDNN 9.1.0.70  | None | ROCm 6.2 |
+| 2.4 | >=3.8, <=3.12 | C++17 | CUDA 11.8, CUDA 12.1, CUDNN 9.1.0.70  | CUDA 12.4, CUDNN 9.1.0.70 | ROCm 6.1 |
+| 2.3 | >=3.8, <=3.11, (3.12 experimental) | C++17 | CUDA 11.8, CUDNN 8.7.0.84 | CUDA 12.1, CUDNN 8.9.2.26 | ROCm 6.0 |
+| 2.2 | >=3.8, <=3.11, (3.12 experimental) | C++17 | CUDA 11.8, CUDNN 8.7.0.84 | CUDA 12.1, CUDNN 8.9.2.26 | ROCm 5.7 |
+| 2.1 | >=3.8, <=3.11 | C++17 | CUDA 11.8, CUDNN 8.7.0.84 | CUDA 12.1, CUDNN 8.9.2.26 | ROCm 5.6 |
+| 2.0 | >=3.8, <=3.11 | C++14 | CUDA 11.7, CUDNN 8.5.0.96 | CUDA 11.8, CUDNN 8.7.0.84 | ROCm 5.4 |
+| 1.13 | >=3.7, <=3.10 | C++14 | CUDA 11.6, CUDNN 8.3.2.44 | CUDA 11.7, CUDNN 8.5.0.96 | ROCm 5.2 |
+| 1.12 | >=3.7, <=3.10 | C++14 | CUDA 11.3, CUDNN 8.3.2.44 | CUDA 11.6, CUDNN 8.3.2.44 | ROCm 5.0 |
 
 ## Release Cadence
 

cmake/MiscCheck.cmake

@@ -7,7 +7,7 @@ set(CAFFE2_USE_EXCEPTION_PTR 1)
 # ---[ Check if we want to turn off deprecated warning due to glog.
 if(USE_GLOG)
   cmake_push_check_state(RESET)
-  set(CMAKE_REQUIRED_FLAGS "-std=c++14")
+  set(CMAKE_REQUIRED_FLAGS "-std=c++17")
   CHECK_CXX_SOURCE_COMPILES(
       "#include <glog/stl_logging.h>
       int main(int argc, char** argv) {

docs/cpp/source/frontend.rst

@@ -1,7 +1,7 @@
 The C++ Frontend
 ================
 
-The PyTorch C++ frontend is a C++14 library for CPU and GPU
+The PyTorch C++ frontend is a C++17 library for CPU and GPU
 tensor computation, with automatic differentiation and high level building
 blocks for state of the art machine learning applications.
 

docs/cpp/source/notes/tensor_basics.rst

@@ -2,7 +2,7 @@ Tensor Basics
 =============
 
 The ATen tensor library backing PyTorch is a simple tensor library that exposes
-the Tensor operations in Torch directly in C++14. ATen's API is auto-generated
+the Tensor operations in Torch directly in C++17. ATen's API is auto-generated
 from the same declarations PyTorch uses so the two APIs will track each other
 over time.
 

ios/LibTorch-Lite-Nightly.podspec.template

@@ -25,7 +25,7 @@ Pod::Spec.new do |s|
     s.user_target_xcconfig = {
         'HEADER_SEARCH_PATHS' => '$(inherited) "$(PODS_ROOT)/LibTorch-Lite-Nightly/install/include/"',
         'OTHER_LDFLAGS' => '-force_load "$(PODS_ROOT)/LibTorch-Lite-Nightly/install/lib/libtorch.a" -force_load "$(PODS_ROOT)/LibTorch-Lite-Nightly/install/lib/libtorch_cpu.a"',
-        'CLANG_CXX_LANGUAGE_STANDARD' => 'c++14',
+        'CLANG_CXX_LANGUAGE_STANDARD' => 'c++17',
         'CLANG_CXX_LIBRARY' => 'libc++'
     }
     s.pod_target_xcconfig = {

ios/LibTorch.podspec.template

@@ -25,7 +25,7 @@ Pod::Spec.new do |s|
     s.user_target_xcconfig = {
         'HEADER_SEARCH_PATHS' => '$(inherited) "$(PODS_ROOT)/LibTorch/install/include/"',
         'OTHER_LDFLAGS' => '-force_load "$(PODS_ROOT)/LibTorch/install/lib/libtorch.a" -force_load "$(PODS_ROOT)/LibTorch/install/lib/libtorch_cpu.a"',
-        'CLANG_CXX_LANGUAGE_STANDARD' => 'c++14',
+        'CLANG_CXX_LANGUAGE_STANDARD' => 'c++17',
         'CLANG_CXX_LIBRARY' => 'libc++'
     }
     s.pod_target_xcconfig = {