1 //******************************************************************************
2 //
3 // File: SharedByte.java
4 // Package: edu.rit.pj.reduction
5 // Unit: Class edu.rit.pj.reduction.SharedByte
6 //
7 // This Java source file is copyright (C) 2007 by Alan Kaminsky. All rights
8 // reserved. For further information, contact the author, Alan Kaminsky, at
9 // ark@cs.rit.edu.
10 //
11 // This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
12 // software; you can redistribute it and/or modify it under the terms of the GNU
13 // General Public License as published by the Free Software Foundation; either
14 // version 3 of the License, or (at your option) any later version.
15 //
16 // PJ is distributed in the hope that it will be useful, but WITHOUT ANY
17 // WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
18 // A PARTICULAR PURPOSE. See the GNU General Public License for more details.
19 //
20 // Linking this library statically or dynamically with other modules is making a
21 // combined work based on this library. Thus, the terms and conditions of the GNU
22 // General Public License cover the whole combination.
23 //
24 // As a special exception, the copyright holders of this library give you
25 // permission to link this library with independent modules to produce an
26 // executable, regardless of the license terms of these independent modules, and
27 // to copy and distribute the resulting executable under terms of your choice,
28 // provided that you also meet, for each linked independent module, the terms
29 // and conditions of the license of that module. An independent module is a module
30 // which is not derived from or based on this library. If you modify this library,
31 // you may extend this exception to your version of the library, but you are not
32 // obligated to do so. If you do not wish to do so, delete this exception
33 // statement from your version.
34 //
35 // A copy of the GNU General Public License is provided in the file gpl.txt. You
36 // may also obtain a copy of the GNU General Public License on the World Wide
37 // Web at http://www.gnu.org/licenses/gpl.html.
38 //
39 //******************************************************************************
40 package edu.rit.pj.reduction;
41
42 import java.io.Serial;
43 import java.util.concurrent.atomic.AtomicInteger;
44
45 /**
46 * Class SharedByte provides a reduction variable for a value of type
47 * <code>byte</code>.
48 * <P>
49 * Class SharedByte is multiple thread safe. The methods use lock-free atomic
50 * compare-and-set.
51 * <P>
52 * <I>Note:</I> Class SharedByte is implemented using class
53 * java.util.concurrent.atomic.AtomicInteger. The byte value is stored as an
54 * <code>int</code> whose values are restricted to the range of type <code>byte</code>.
55 *
56 * @author Alan Kaminsky
57 * @version 07-Jun-2007
58 */
59 public class SharedByte
60 extends Number {
61
62 @Serial
63 private static final long serialVersionUID = 1L;
64
65 // Hidden data members.
66 private AtomicInteger myValue;
67
68 // Exported constructors.
69 /**
70 * Construct a new byte reduction variable with the initial value 0.
71 */
72 public SharedByte() {
73 myValue = new AtomicInteger();
74 }
75
76 /**
77 * Construct a new byte reduction variable with the given initial value.
78 *
79 * @param initialValue Initial value.
80 */
81 public SharedByte(byte initialValue) {
82 myValue = new AtomicInteger(initialValue);
83 }
84
85 // Exported operations.
86 /**
87 * Returns this reduction variable's current value.
88 *
89 * @return Current value.
90 */
91 public byte get() {
92 return (byte) myValue.get();
93 }
94
95 /**
96 * Set this reduction variable to the given value.
97 *
98 * @param value New value.
99 */
100 public void set(byte value) {
101 myValue.set(value);
102 }
103
104 /**
105 * Set this reduction variable to the given value and return the previous
106 * value.
107 *
108 * @param value New value.
109 * @return Previous value.
110 */
111 public byte getAndSet(byte value) {
112 return (byte) myValue.getAndSet(value);
113 }
114
115 /**
116 * Atomically set this reduction variable to the given updated value if the
117 * current value equals the expected value.
118 *
119 * @param expect Expected value.
120 * @param update Updated value.
121 * @return True if the update happened, false otherwise.
122 */
123 public boolean compareAndSet(byte expect,
124 byte update) {
125 return myValue.compareAndSet(expect, update);
126 }
127
128 /**
129 * Atomically set this reduction variable to the given updated value if the
130 * current value equals the expected value. May fail spuriously.
131 *
132 * @param expect Expected value.
133 * @param update Updated value.
134 * @return True if the update happened, false otherwise.
135 */
136 @SuppressWarnings("deprecation")
137 public boolean weakCompareAndSet(byte expect,
138 byte update) {
139 return myValue.weakCompareAndSet(expect, update);
140 }
141
142 /**
143 * Add one to this reduction variable and return the previous value.
144 *
145 * @return Previous value.
146 */
147 public byte getAndIncrement() {
148 for (;;) {
149 byte oldvalue = (byte) myValue.get();
150 byte newvalue = (byte) (oldvalue + 1);
151 if (myValue.compareAndSet(oldvalue, newvalue)) {
152 return oldvalue;
153 }
154 }
155 }
156
157 /**
158 * Subtract one from this reduction variable and return the previous value.
159 *
160 * @return Previous value.
161 */
162 public byte getAndDecrement() {
163 for (;;) {
164 byte oldvalue = (byte) myValue.get();
165 byte newvalue = (byte) (oldvalue - 1);
166 if (myValue.compareAndSet(oldvalue, newvalue)) {
167 return oldvalue;
168 }
169 }
170 }
171
172 /**
173 * Add the given value to this reduction variable and return the previous
174 * value.
175 *
176 * @param value Value to add.
177 * @return Previous value.
178 */
179 public byte getAndAdd(byte value) {
180 for (;;) {
181 byte oldvalue = (byte) myValue.get();
182 byte newvalue = (byte) (oldvalue + value);
183 if (myValue.compareAndSet(oldvalue, newvalue)) {
184 return oldvalue;
185 }
186 }
187 }
188
189 /**
190 * Add one to this reduction variable and return the new value.
191 *
192 * @return New value.
193 */
194 public byte incrementAndGet() {
195 for (;;) {
196 byte oldvalue = (byte) myValue.get();
197 byte newvalue = (byte) (oldvalue + 1);
198 if (myValue.compareAndSet(oldvalue, newvalue)) {
199 return newvalue;
200 }
201 }
202 }
203
204 /**
205 * Subtract one from this reduction variable and return the new value.
206 *
207 * @return New value.
208 */
209 public byte decrementAndGet() {
210 for (;;) {
211 byte oldvalue = (byte) myValue.get();
212 byte newvalue = (byte) (oldvalue - 1);
213 if (myValue.compareAndSet(oldvalue, newvalue)) {
214 return newvalue;
215 }
216 }
217 }
218
219 /**
220 * Add the given value to this reduction variable and return the new value.
221 *
222 * @param value Value to add.
223 * @return New value.
224 */
225 public byte addAndGet(byte value) {
226 for (;;) {
227 byte oldvalue = (byte) myValue.get();
228 byte newvalue = (byte) (oldvalue + value);
229 if (myValue.compareAndSet(oldvalue, newvalue)) {
230 return newvalue;
231 }
232 }
233 }
234
235 /**
236 * Combine this reduction variable with the given value using the given
237 * operation. The result is stored back into this reduction variable and is
238 * returned.
239 *
240 * @param value Value.
241 * @param op Binary operation.
242 * @return (This variable) <I>op</I> (<code>value</code>).
243 */
244 public byte reduce(byte value,
245 ByteOp op) {
246 for (;;) {
247 byte oldvalue = (byte) myValue.get();
248 byte newvalue = op.op(oldvalue, value);
249 if (myValue.compareAndSet(oldvalue, newvalue)) {
250 return newvalue;
251 }
252 }
253 }
254
255 /**
256 * Returns a string version of this reduction variable.
257 *
258 * @return String version.
259 */
260 public String toString() {
261 return Integer.toString(get());
262 }
263
264 /**
265 * Returns this reduction variable's current value converted to type
266 * <code>int</code>.
267 *
268 * @return Current value.
269 */
270 public int intValue() {
271 return get();
272 }
273
274 /**
275 * Returns this reduction variable's current value converted to type
276 * <code>long</code>.
277 *
278 * @return Current value.
279 */
280 public long longValue() {
281 return get();
282 }
283
284 /**
285 * Returns this reduction variable's current value converted to type
286 * <code>float</code>.
287 *
288 * @return Current value.
289 */
290 public float floatValue() {
291 return get();
292 }
293
294 /**
295 * Returns this reduction variable's current value converted to type
296 * <code>double</code>.
297 *
298 * @return Current value.
299 */
300 public double doubleValue() {
301 return get();
302 }
303
304 }