Context : 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 .

Aims : 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 .

Methods : Supernova parameters are determined by means of the standard hydrodynamic modeling .
The early hydrogen H \alpha and H \beta 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 .

Results : We found that SN 20012A is the result of the explosion of a red supergiant with the radius of 715 \pm 100 ~ { } R _ { \sun } .
The explosion energy is ( 5.25 \pm 0.6 ) \times 10 ^ { 50 } erg , the ejecta mass is 13.1 \pm 0.7 ~ { } M _ { \sun } , and the total ^ { 56 } Ni mass is 0.012 \pm 0.002 ~ { } M _ { \sun } .
The estimated mass of a progenitor , a main-sequence star , is 15 \pm 1 ~ { } M _ { \sun } .
The H \alpha and H \beta 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 .

Conclusions : The pre-SN 2012A was a normal red supergiant with the progenitor mass of \approx 15 ~ { } M _ { \sun } .
The outer layers of ejecta indicate the clumpy structure .
The clumpiness of the external layers can increase the maximum expansion velocity .