Channel Allocation, Beam Laydown,
of several specialized algorithms
for Motorola for use on the Iridium
project. Some of this work resulted
in US Patent No. 5,826,189 (in the
name of Dr. Thapa), through Motorola,
in the area of efficient channel allocation
for satellite communications. Other
innovative approaches were developed
for Beam Laydown, and for call switching.
current Bidding Model for pipeline
capacity for PG&E was enhanced.
The existing linear programming model
was enhanced (1) to generate unique
solutions through the use of quadratic
programming techniques, and; (2) to
handle Minimum Acceptable Quantities
through the use of branch bound techniques.
For the purpose of this task, a version
of MINOS was customized.
is a FORTRAN program designed to solve
chemical equilibrium problems using
a free energy minimization approach.
The associated optimization problem
is a nonlinear program with linear
equality constraints. The code utilizes
the numerically stable LINPACK routines
to perform most of the critical numerical
linear algebra. GMIN has been used
in several geochemical applications.
SBSI’s work with GMIN involved
modifying the code in order to improve
its efficiency. First, GMIN was altered
to allocate memory dynamically depending
on problem size. This change permits
a significant reduction in the total
memory required for the program to
run, which is especially important
under the 640K limitation under which
many programs run. Second, many efficient
enhancements to the code were implemented.
Some of these changes involved optimizations
to the individual FORTRAN routines
such as bringing constant expressions
outside loops, reducing array accesses,
and simplifying statements. Other
changes were more elaborate. For example,
GMIN’s routines to update a
QR factorization were altered to do
the task using vector inner products
instead of matrix products. The result
was a reduction in both computing
time and memory. Finally, during the
course of the above mentioned tasks
a few previously existing bugs in
the code were discovered and corrected.