Cause 1: Structures having Eigen objects as members

If you have code like this,

class Foo

{

//...

v;

//...

};

//...

Foo *foo = new Foo;

then you need to read this separate page: .

Note that here, is only used as an example, more generally the issue arises for all .

Cause 2: STL Containers

If you use STL Containers such as std::vector, std::map, ..., with objects, or with classes containing objects, like this,

std::vector<Eigen::Matrix2f> my_vector;

struct my_class { ... m; ... };

std::map<int, my_class> my_map;

then you need to read this separate page: .

Note that here, is only used as an example, more generally the issue arises for all and .

Cause 3: Passing Eigen objects by value

If some function in your code is getting an object passed by value, like this,

void func( v);

then you need to read this separate page: .

Note that here, is only used as an example, more generally the issue arises for all .

Cause 4: Compiler making a wrong assumption on stack alignment (for instance GCC on Windows)

This is a must-read for people using GCC on Windows (like MinGW or TDM-GCC). If you have this assertion failure in an innocent function declaring a local variable like this:

void foo()

{

q;

//...

}

then you need to read this separate page: .

Note that here, is only used as an example, more generally the issue arises for all .

Explanation

must absolutely be created at 16-byte-aligned locations, otherwise SIMD instructions adressing them will crash.

normally takes care of these alignment issues for you, by setting an alignment attribute on them and by overloading their "operator new".

However there are a few corner cases where these alignment settings get overridden: they are the possible causes for this assertion.

I don't care about vectorization, how do I get rid of that stuff?

Two possibilities:

• Define EIGEN_DONT_ALIGN_STATICALLY. That disables all 128-bit static alignment code, while keeping 128-bit heap alignment. This has the effect of disabling vectorization for fixed-size objects (like Matrix4d) while keeping vectorization of dynamic-size objects (like MatrixXd). But do note that this breaks ABI compatibility with the default behavior of 128-bit static alignment.
• Or define both EIGEN_DONT_VECTORIZE and EIGEN_DISABLE_UNALIGNED_ARRAY_ASSERT. This keeps the 128-bit alignment code and thus preserves ABI compatibility, but completely disables vectorization.