eigen/doc/I14_PreprocessorDirectives.dox

namespace Eigen {

/** \page TopicPreprocessorDirectives Preprocessor directives

You can control some aspects of Eigen by defining the following preprocessor tokens them before including any of Eigen's headers.
 - \b EIGEN_NO_DEBUG If defined, Eigen's assertions are disabled. Disabling run-time assertions improves the
   performance, but it is dangerous because the assertions guard against programming errors. By default, the
   EIGEN_NO_DEBUG macro is not defined and Eigen's run-time assertions are thus enabled. However, if the
   NDEBUG macro is defined (this is a standard C++ macro which disables all asserts), then the EIGEN_NO_DEBUG
   macro will also be defined, and so Eigen's assertions will also be disabled. 
 - \b EIGEN_DONT_VECTORIZE disables explicit vectorization when defined.
 - \b EIGEN_UNROLLING_LIMIT defines the maximal instruction counts to enable meta unrolling of loops. Set it to zero to disable unrolling. The default is 100.
 - \b EIGEN_DEFAULT_TO_ROW_MAJOR the default storage order for matrices becomes row-major instead of column-major.
 - \b EIGEN_TUNE_FOR_CPU_CACHE_SIZE represents the maximal size in Bytes of L2 blocks. Since several blocks have to stay concurently in L2 cache, this value should correspond to at most 1/4 of the size of L2 cache.
 - \b EIGEN_NO_STATIC_ASSERT replaces compile time static assertions by runtime assertions
 - \b EIGEN_MATRIXBASE_PLUGIN see \ref ExtendingMatrixBase

*/

}