This is a standard C++ program with Standard Template Library (STL) used.
This package converts the PSSM, generated by PSI-Blast, into a fixed-length vector by the ACC algorithm.
Reference:
Qiwen Dong, Shuigeng Zhou, Jihong Guan.
Protein fold recognition based on auto-cross covariance transformation.
Bioinformatics, 2009.
The source code can be downloaded here.