  The explosion energy and the ejecta mass of a type IIP supernova (SN IIP)
derived from hydrodynamic simulations are principal parameters of the explosion
theory. However, the number of SNe IIP studied by hydrodynamic modeling is
small. Moreover, some doubts exist in regard to the reliability of derived SN
IIP parameters. The well-observed type IIP SN 2012A will be studied via
hydrodynamic modeling. Their early spectra will be checked for a presence of
the ejecta clumpiness. Other observational effects of clumpiness will be
explored. Supernova parameters are determined by means of the standard
hydrodynamic modeling. The early hydrogen Halpha and Hbeta lines are used for
the clumpiness diagnostics. The modified hydrodynamic code is employed to study
the clumpiness effect in the light curve and expansion kinematics. We found
that SN 20012A is the result of the explosion of a red supergiant with the
radius of 715 Rsun. The explosion energy is 5.25x10^50 erg, the ejecta mass is
13.1 Msun, and the total Ni-56 mass is 0.012 Msun. The estimated mass of a
progenitor, a main-sequence star, is 15 Msun. The Halpha and Hbeta lines in
early spectra indicate that outer ejecta are clumpy. Hydrodynamic simulations
show that the clumpiness modifies the early light curve and increases the
maximum velocity of the outer layers. The pre-SN 2012A was a normal red
supergiant with the progenitor mass of about 15 Msun. The outer layers of
ejecta indicate the clumpy structure. The clumpiness of the external layers can
increase the maximum expansion velocity.
