Self doubt

Question

How to solve the question involving the calculation of safe sequence when the resource allocation graph is given instead of the table. Eg. In the question below..What should be the approach to solve the question??? Plzz explain..

Answer 1

just take the prior knowledge of DAG representation means which one is requesting edge which one is allocated edge ... like this one

and construct the table which u are asking for ,but without table we can also solve just using the basic knowledge of DAG

for example p1 has two allocated edges 1 insatnce of R1 and one of R3 is allocated to it .and p1 has one requesting edge requestiong for one instance ogf R3........simlarly do for all

Answer 2

if you are comfortable with tables, just make the diagram into table...

in that case, there is only allocated matrix and need matrix but there is no Maximum demand matrix

out going edges from a process should represent remaining need resources and

incoming edges to the process should represent allocated resources

 

                       allocated                             need

                    R1      R2    R3                  R1     R2      R3

P1                1         0       1                   0         0         1

P2                1         1       0                   0         1         1

P3                0         1       1                   0         1         0

P4                0         0       0                   0         1         1

---------------------------------------------------------------------------

Allocated     2            2        2

Total           2             3        2

------------------------------------------

Available     0            1        0

 

 

i can complete P3, ===> Available     0            2        1

now i can complete any processes ===> More than one safe sequence exist