Banker's algorithm: Difference between revisions

my @processes = <0 1 2>;

my @avail = <3 1 1 2>; # Available instances of resource

# Maximum R that can be allocated to processes

my @maxm = <3 3 2 2>, <1 2 3 4>, <1 3 5 0>;

# Resources allocated to processes

my @allot = <1 2 2 1>, <1 0 3 3>, <1 2 1 0>;

sub isSafe(\processes, \avail, \maxm, \allot) {

my $satisfied;

my @need; # the need matrix

for ^P -> \i { # Calculating Need of each P

for ^R -> \j { # Need of instance = maxm instance - allocated instance

@need[i;j] = @maxm[i;j] - @allot[i;j]

}

}

my @finish = 0 xx P; # Mark all processes as infinish

my @safeSeq = 0 xx P; # To store safe sequence

my @work = 0 xx R; # Make a copy of available resources

for ^R -> \i { @work[i] = avail[i] }

# While all processes are not finished or system is not in safe state

my $count = 0;

while $count < P { # Find a process which is not finish and whose needs

# can be satisfied with current @work resources.

my $found = False;

for ^P -> \p {

# First check if a process is finished, if no, go for next condition

if @finish[p] == 0 {

# Check if for all resources of current P need is less than work

LOOP: for ^R -> \j {

$satisfied = j;

last LOOP if @need[p;j] > @work[j]

}

if $satisfied == R - 1 { # If all needs of p were satisfied.

# Add the allocated resources of current P to the

# available/work resources i.e.free the resources

for ^R -> \k { @work[k] += allot[p;k] }

# Add this process to safe sequence.

@safeSeq[$count] = p;

$count += 1;

# Mark this p as finished

@finish[p] = 1;

$found = True

}

}

# If we could not find a next process in safe sequence.

return False, "System is not in safe state." unless $found;

}

# If system is in safe state then safe sequence will be as below

True, "Safe sequence is: " ~ @safeSeq

my ($safe-state,$status-message) = isSafe @processes, @avail, @maxm, @allot;