Table 5.9
illustrates the speed of the ScaLAPACK driver
routine PSGESV /PDGESV
for solving a square linear system of order *N* by
LU factorization with partial row pivoting of a real
matrix. For all timings, 64-bit floating-point arithmetic was used.
Thus, single-precision timings are reported for
the Cray T3E, and double precision timings are reported
on all other computers. The distribution block size is
also used as the partitioning unit for the computation and
communication phases.

Table 5.10
illustrates the speed of the ScaLAPACK routine
PSPOSV /PDPOSV for
solving a symmetric positive definite linear system of
order *N* via the Cholesky factorization.

Right-looking variants of the *LU* and Cholesky factorizations
were chosen for ScaLAPACK because they minimize total communication
volume, that is, the aggregated

**Table 5.9:** Speed in Mflop/s of PSGESV/PDGESV for square
matrices of order *N*

amount of data transferred between processes during the operation.

**Table 5.10:** Speed in Mflop/s of PSPOSV/PDPOSV for matrices of
order *N* with UPLO=`U'

Tue May 13 09:21:01 EDT 1997