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SS9 MINIMUM PREEMPTIVE
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Multiprocessor Scheduling
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SS7 MINIMUM PRECEDENCE
-
I
NSTANCE
:
Set
T
of tasks each having length
l(t)
, number
m
of processors, number
r
of resources, resource bounds
,
, and resource
requirement
,
, for each task
t
and
resource
i
.
-
S
OLUTION
:
An
m
processor schedule for
T
that obeys the resource constraints, i.e., a
function
such that for all
, if
S(u)
is
the set
of tasks
t
for which
, then
and for
each resource
i
-
M
EASURE
:
The makespan of the schedule, i.e.,
.
-
Good News:
Approximable within 2 [
120
].
-
Comment:
Note that the restriction in which there is only one resource, i.e.,
the available processors, is identical to minimizing the makespan of
the schedule of parallel tasks on
m
processors. In this case,
minimizing the average response time, i.e.,
is approximable within 32 [
334
].
The further variation in which each task can be executed by any number
of processors and the length of a task is a function of the number of
processors allotted to it is also approximable [
262
].
Variation in which every task is of length 1 and has an integer
ready-time, which means that it cannot be processed before its
ready-time, is approximable [
328
].
-
Garey and Johnson:
SS10
Viggo Kann
Mon Apr 21 13:07:14 MET DST 1997