GitLab

* Fix cannot compile iso only code (#579)

also fixing (#1742)

* Remove GUI dependency from fonts (#2273)

* Fix disable_duplicative_biases when the input is a skip layer

* fix template parameters

* try to make sure travis uses C++17

* fix unbound variable

* Update dlib/travis/build-and-test.sh
Co-authored-by: Davis E. King <davis@dlib.net>

* Fix serialize variant with C++17

* fix order of parameters

* added support for std::optional if using C++

* oops, bug fix + check if item already holds a type

* oops, another bug fix

* remove warnings about unused parameters
Co-authored-by: pf <pf@me>

* [SERIALIZATION] addes support for std::variant

* [SERIALIZATION] bug fix + added tests

* support immutable types

* put an immutable type in std::variant
Co-authored-by: pf <pf@me>

Do this by just making all layers have a .input_layer() method, which in
that context can be implemented in a simple manner.

Also fix this error from cmake 3.5.1:

```
CMake Error at CMakeLists.txt:62 (if):
  if given arguments:

    "CMAKE_COMPILER_IS_GNUCXX" "AND" "CMAKE_CXX_COMPILER_VERSION" "VERSION_LESS_EQUAL" "4.8.5"

  Unknown arguments specified
```

* do not attempt to build with gcc 4.8.5 or older

* add comment

* [TYPE_SAFE_UNION] use std::aligned_union instead of stack_based_memory_block. std::aligned_union was specifically designed to do this kind of stuff and we are better off trusting the standard library deciding what the correct storage type should be and what the appropriate alignment should be

* [TYPE_SAFE_UNION] as per Davis' suggestion, std::aligned_union can take Len parameter 0. Also, the content's of validate_type() has been bugging me for ages, so i created is_any which is based on std::is_same. I've also replaced is_same_type with std::is_same
Co-authored-by: Peter Featherstone <peter@grampus-server.com>

* Make ELU an inplace layer

* Fix CUDA implementation of clipped_relu and update tests

* wip: add apis for clipped_relu and elu, and layer implementation for clipped_relu

* add tensor_tools documentation

* add cpu implementations for new activations

* add elu layer

* use upperbound and lowerbound for clipped_relu

* fix clipped_relu gradient due to wrong variable naming

* fix elu_gradient due to wrong variable naming

* fix elu_gradient documentation

* add documentation

* WIP: add test_layer cases for clipped_relu and elu

For some reason that I can't see, ELU is failing...

* add clipped_relu and elu tests... cuda elu layer still does not work

* fix spacing

* add custom cuda implementation for elu_gradient (this one works)

* Revert "add custom cuda implementation for elu_gradient (this one works)"

This reverts commit 446dd803964cc6ecca598ddf6688e5d89ca0b112.

* Revert "Revert "add custom cuda implementation for elu_gradient (this one works)""

This reverts commit 0b615f50081d0d90e71d502b6767fcb6ba62f28a.

* add comment about custom elu gradient implementation

* add gradient tests, restore cudnn elu gradient

* re add custom elu gradient implementation

* update docs

* use own cuda implementation for clipped_relu and elu
Co-authored-by: Davis E. King <davis@dlib.net>

* Fix input/output mappings with repeat layers

* add test for input/output tensor mappers

* fix output to input order

* Add letterbox image

* use && instead of and

* make function adhere to the generic image interface

* avoid extra copy

* add some overloads and a simple test

* add documentation

* use zero_border_pixels and remove superfluous temporary image

* allow different input and out images and update docs

* remove empty line

* be more explicit about output image size

* Add softmax function for matrix type

* make softmax inherit from basic_op_m

* fix comment

* add test for matrix softmax

* remove include

* take inspiration from op_normalize

* use multiplication instead of division

* fix typo in documentation

This reverts commit 8b9d0439.

Reverting this because the cmake pip pakage is still busted.  I've been
getting messages from many people about how it's breaking their
systems/installs.