  The final fate of the spherically symmetric collapse of a perfect fluid which
follows the $\gamma$-law equation of state and adiabatic condition is
investigated. Full general relativistic hydrodynamics is solved numerically
using a retarded time coordinate, the so-called observer time coordinate.
Thanks to this coordinate, the causal structure of the resultant space-time is
automatically constructed. Then, it is found that a globally naked,
shell-focusing singularity can occur at the center from relativistically
high-density, isentropic and time symmetric initial data if $\gamma \alt 1.01$
within the numerical accuracy. The result is free from the assumption of
self-similarity. The upper limit of $\gamma$ with which a naked singularity can
occur from generic initial data is consistent with the result of Ori and Piran
based on the assumption of self-similarity.
