  Gyrosynchrotron (GS) emission of charged particles spiraling in magnetic
fields plays an exceptionally important role in astrophysics. In particular,
this mechanism makes a dominant contribution to the continuum solar and stellar
radio emissions. However, the available exact equations describing the emission
process are extremely slow computationally, thus limiting the diagnostic
capabilities of radio observations. In this work, we present approximate GS
codes capable of fast calculating the emission from anisotropic electron
distributions. The computation time is reduced by several orders of magnitude
compared with the exact formulae, while the computation error remains within a
few percent. The codes are implemented as the executable modules callable from
IDL; they are made available for users via web sites.
