Implementation of Banker’s Algorithm in JAVA
The program will read a data file. The name of the data file will be provided as a command line argument. The data file will have the following structure:
First row will represent the maximum units of each resource. There can be any number of resources.
Second row will contain new request by a process. The first number will be PID i.e process ID of the process making the request and subsequent numbers will be the amount/number of units of each resource the process is requesting.
Subsequent rows will contain Allocation & Max information about each process. An example file is as follows:
0 1 0 7 5 3
2 0 0 3 2 2
3 0 2 9 0 2
2 1 1 2 2 2
0 0 2 4 3 3
In the above file, the first line tells us that there are 10 units of resource R1, 5 units of R2 and 7 units of R3 in the system.
The second line tells that process P1 has requested 1 unit of resource R1, 0 units of R2 and 2 units of R3.
The third line tells that process P0 has been allocated 0 units of R1, 1 unit of R2 and 0 units of R3; and maximum demand of P0 is 7 units of R1, 5 units of R2 and 3 units of R3.
Java Banker Input.txt
First row will represent the maximum units of each resource. There can be any number of resources.
Second row will contain new request by a process. The first number will be PID i.e process ID of the process making the request and subsequent numbers will be the amount/number of units of each resource the process is requesting.
Subsequent rows will contain Allocation & Max information about each process. An example file is as follows:
10 5 7
1 1 0 20 1 0 7 5 3
2 0 0 3 2 2
3 0 2 9 0 2
2 1 1 2 2 2
0 0 2 4 3 3
In the above file, the first line tells us that there are 10 units of resource R1, 5 units of R2 and 7 units of R3 in the system.
The second line tells that process P1 has requested 1 unit of resource R1, 0 units of R2 and 2 units of R3.
The third line tells that process P0 has been allocated 0 units of R1, 1 unit of R2 and 0 units of R3; and maximum demand of P0 is 7 units of R1, 5 units of R2 and 3 units of R3.
Code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 | import java.util.*; import java.io.*; public class Banker{ public static void main(String args[]) throws IOException{ int total[]=null,line=1,newRequest[]=null,pid=0,resources=0,available[]=null; ArrayList<int[]> allocation = new ArrayList<int[]>(); ArrayList<int[]> demand = new ArrayList<int[]>(); ArrayList<int[]> need = new ArrayList<int[]>(); ArrayList<String> sequence = new ArrayList<String>(); boolean[] completedProcess=null; if(args.length==0){ System.out.println("File Not Provided"); return; } Scanner scanner = new Scanner(new File(args[0])); while(scanner.hasNextLine()){ String str = scanner.nextLine(); String arr[]; if(line>2){ arr = str.trim().split("\\s+"); int allocated[]=new int[resources]; int processDemand[]=new int[resources]; for(int i=0;i<arr.length;i++){ if(i<(arr.length/2)){ allocated[i]=Integer.parseInt(arr[i]); available[i]=available[i]-allocated[i]; }else processDemand[i-(arr.length/2)]=Integer.parseInt(arr[i]); } allocation.add(allocated); demand.add(processDemand); continue; } if(line==1){ arr = str.trim().split("\\s+"); total = new int[arr.length]; available = new int[arr.length]; resources = arr.length; for(int i=0;i<arr.length;i++){ total[i] = Integer.parseInt(arr[i]); } available = Arrays.copyOf(total,total.length); line++; }else if(line==2){ arr = str.trim().split("\\s+"); newRequest = new int[arr.length]; for(int i=0;i<arr.length;i++){ newRequest[i] = Integer.parseInt(arr[i]); } line++; } } for(int i=0;i<allocation.size();i++){ int allocated[] = allocation.get(i); int processDemand[] = demand.get(i); int needOfProcess[] = new int[allocated.length]; for(int j=0;j<allocated.length;j++){ needOfProcess[j]=processDemand[j]-allocated[j]; } need.add(needOfProcess); } boolean flag = false; completedProcess = new boolean[allocation.size()]; for(int i=1;i<newRequest.length;i++){ if(newRequest[i]<=available[i-1]){ flag = true; }else{ flag = false; break; } } if(flag){ int[] allocated,needOfProcess; allocated = allocation.get(newRequest[0]); needOfProcess = need.get(newRequest[0]); for(int i=0;i<available.length;i++){ allocated[i]+=newRequest[i+1]; available[i]-=newRequest[i+1]; needOfProcess[i]-=newRequest[i+1]; } }else{ System.out.println("\nNot enough resources: Request Denied"); return; } int totalCompletedProcess=0; int completedProcessLastTime=-1; while(!isAllTrue(completedProcess)){ flag=false; if(totalCompletedProcess==completedProcessLastTime){ System.out.println("\nNo sequence to satisfy safety criteria: Request Denied"); return; } completedProcessLastTime=totalCompletedProcess; for(int i=0;i<need.size();i++){ if(completedProcess[i]) continue; int[] needOfProcess = need.get(i); for(int j=0;j<available.length;j++){ if(needOfProcess[j]<=available[j]){ flag = true; }else{ flag = false; break; } } if(flag){ int[] allocated; allocated = allocation.get(i); for(int j=0;j<available.length;j++){ available[j]+=allocated[j]; allocated[j]-=allocated[j]; needOfProcess[j]-=needOfProcess[j]; } completedProcess[i]=true; totalCompletedProcess++; sequence.add("P"+i+" "); } } } System.out.println("\nSequence "+sequence.toString()+" satisfy safety criteria: Request Granted"); } public static boolean isAllTrue(boolean[] completedProcess){ for(int i=0;i<completedProcess.length;i++){ if(!completedProcess[i]){ return false; } } return true; } } |
Output:
The output of each run will either produce a sequence of processes that satisfies the safety criteria if we grant the request or report that this request should not be granted and the reason for denial.Java Banker Input.txt
Sequence [P1 , P3 , P4 , P0 , P2 ] satisfy safety criteria: Request Granted
If the second line in the above file is modified to
4 3 3 0
Java Banker Input.txt
No sequence to satisfy safety criteria: Request Denied
If the second line in the above file is modified to
1 1 0 5
Java Banker Input.txt
Not enough resources: Request Denied
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