Intel® MPI Library Reference Manual for Linux* OS
Each collective operation in the Intel® MPI Library supports a number of communication algorithms. In addition to highly optimized default settings, the library provides a way to control the algorithm selection explicitly: I_MPI_ADJUST environment variable family, which is described in the following section.
The environment variable is available for both Intel® and non-Intel microprocessors, but it may perform additional optimizations for Intel microprocessors than it performs for non-Intel microprocessors.