OpenMP Application Programming Interface Examples

More documents

Recommendations

Info

1 CHAPTER 1 2 Parallel Execution 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 A single thread, the initial thread, begins sequential execution of an OpenMP enabled program, as if the whole program is in an implicit parallel region consisting of an implicit task executed by the initial thread. A parallel construct encloses code, forming a parallel region. An initial thread encountering a parallel region forks (creates) a team of threads at the beginning of the parallel region, and joins them (removes from execution) at the end of the region. The initial thread becomes the master thread of the team in a parallel region with a thread number equal to zero, the other threads are numbered from 1 to number of threads minus 1. A team may be comprised of just a single thread. Each thread of a team is assigned an implicit task consisting of code within the parallel region. The task that creates a parallel region is suspended while the tasks of the team are executed. A thread is tied to its task; that is, only the thread assigned to the task can execute that task. After completion of the parallel region, the master thread resumes execution of the generating task. Any task within a parallel region is allowed to encounter another parallel region to form a nested parallel region. The parallelism of a nested parallel region (whether it forks additional threads, or is executed serially by the encountering task) can be controlled by the OMP_NESTED environment variable or the omp_set_nested() API routine with arguments indicating true or false. The number of threads of a parallel region can be set by the OMP_NUM_THREADS environment variable, the omp_set_num_threads() routine, or on the parallel directive with the num_threads clause. The routine overrides the environment variable, and the clause overrides all. Use the OMP_DYNAMIC or the omp_set_dynamic() function to specify that the OpenMP implementation dynamically adjust the number of threads for parallel regions. The default setting for dynamic adjustment is implementation defined. When dynamic adjustment is on and the number of threads is specified, the number of threads becomes an upper limit for the number of threads to be provided by the OpenMP runtime. 3
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 WORKSHARING CONSTRUCTS A worksharing construct distributes the execution of the associated region among the members of the team that encounter it. There is an implied barrier at the end of the worksharing region (there is no barrier at the beginning). The worksharing constructs are: • loop constructs: for and do • sections • single • workshare The for and do constructs (loop constructs) create a region consisting of a loop. A loop controlled by a loop construct is called an associated loop. Nested loops can form a single region when the collapse clause (with an integer argument) designates the number of associated loops to be executed in parallel, by forming a "single iteration space" for the specified number of nested loops. The ordered clause can also control multiple associated loops. An associated loop must adhere to a "canonical form" (specified in the Canonical Loop Form of the OpenMP Specifications document) which allows the iteration count (of all associated loops) to be computed before the (outermost) loop is executed. Most common loops comply with the canonical form, including C++ iterators. A single construct forms a region in which only one thread (any one of the team) executes the region. The other threads wait at the implied barrier at the end, unless the nowait clause is specified. The sections construct forms a region that contains one or more structured blocks. Each block of a sections directive is constructed with a section construct, and executed once by one of the threads (any one) in the team. (If only one block is formed in the region, the section construct, which is used to separate blocks, is not required.) The other threads wait at the implied barrier at the end, unless the nowait clause is specified. The workshare construct is a Fortran feature that consists of a region with a single structure block (section of code). Statements in the workshare region are divided into units of work, and executed (once) by threads of the team. 29 30 31 32 MASTER CONSTRUCT The master construct is not a worksharing construct. The master region is is executed only by the master thread. There is no implicit barrier (and flush) at the end of the master region; hence the other threads of the team continue execution beyond code statements beyond the master region. 4 OpenMP Examples Version 4.5.0 - November 2016
Page 1 and 2: OpenMP Application Programming Inte
Page 3 and 4: Contents Introduction 1 Examples 2
Page 5 and 6: 4.5.3. declare target and end decla
Page 7 and 8: 9.5. Nested Loop Constructs . . . .
Page 9: 1 Examples 2 3 4 5 6 7 8 9 10 11 Th
Page 13 and 14: 1 2 3 4 5 1.2 The parallel Construc
Page 15 and 16: 1 2 3 4 5 1.3 Controlling the Numbe
Page 17 and 18: S-29 !$omp single S-30 ! If OMP_NUM
Page 19 and 20: 1 2 3 4 Example nthrs_dynamic.2.c C
Page 21 and 22: S-7 S-8 DO 100 I = 1,10 S-9 !$OMP D
Page 23 and 24: S-19 ENDDO S-20 !$OMP END DO NOWAIT
Page 25 and 26: 1 2 3 4 5 6 7 8 9 10 11 12 1.7 The
Page 27 and 28: Fortran 1 2 3 4 5 6 7 8 9 10 11 12
Page 29 and 30: 1 2 3 4 5 6 1.8 linear Clause in Lo
Page 31 and 32: 1 2 3 4 5 6 1.9 The parallel sectio
Page 33 and 34: Fortran 1 Example fpriv_sections.1.
Page 35 and 36: Fortran 1 Example single.1.f S-1 SU
Page 37 and 38: Fortran (cont.) 1 2 3 4 5 6 7 8 9 1
Page 39 and 40: S-14 S-15 END SUBROUTINE WSHARE6_WR
Page 41 and 42: Fortran 1 Example master.1.f S-1 SU
Page 43 and 44: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1.
Page 45 and 46: 1 2 3 4 5 6 1.16 The omp_get_num_th
Page 47 and 48: 1 CHAPTER 2 2 OpenMP Affinity 3 4 5
Page 49 and 50: 1 2 3 4 5 6 2.1 The proc_bind Claus
Page 51 and 52: Fortran 1 2 3 4 5 6 7 8 9 10 11 12
Page 53 and 54: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 55 and 56: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 57 and 58: S-24 S-25 socket_num = omp_get_plac
Page 59 and 60: 1 2 3 4 5 6 7 8 3.1 The task and ta
Page 61 and 62:
Fortran 1 2 3 4 5 The following exa
Page 63 and 64:
1 2 3 4 5 6 7 8 9 10 Example taskin
Page 65 and 66:
Fortran 1 2 3 4 5 6 7 8 9 10 11 Exa
Page 67 and 68:
1 2 Example tasking.7.c C / C++ S-1
Page 69 and 70:
Fortran 1 2 3 4 5 6 7 8 9 Example t
Page 71 and 72:
1 2 Example tasking.10.c C / C++ S-
Page 73 and 74:
Fortran 1 2 3 4 5 6 7 Example taski
Page 75 and 76:
S-16 state = new_state; S-17 } S-18
Page 77 and 78:
Fortran 1 Example tasking.14.f90 S-
Page 79 and 80:
S-17 call compute_array(matrix(:, i
Page 81 and 82:
Fortran 1 2 3 The program will alwa
Page 83 and 84:
1 2 3 4 S-13 printf("x = %d\n", x);
Page 85 and 86:
Fortran 1 2 3 4 5 The last two task
Page 87 and 88:
1 2 3 4 5 6 7 8 9 10 3.4 The taskgr
Page 89 and 90:
S-22 endif S-23 !$omp task S-24 cal
Page 91 and 92:
S-13 call something_critical() S-14
Page 93 and 94:
Fortran 1 Example taskloop.1.f90 S-
Page 95 and 96:
1 2 3 4 5 6 4.1 target Construct 4.
Page 97 and 98:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 99 and 100:
1 2 3 4 5 6 7 8 9 C / C++ In C, the
Page 101 and 102:
1 2 3 4 5 6 7 S-12 for (i=0; iTHRES
Page 103 and 104:
1 2 3 4 5 6 7 8 9 10 11 4.2 target
Page 105 and 106:
1 2 3 4 5 6 Example target_data.2.c
Page 107 and 108:
1 2 3 4 5 6 C / C++ In the followin
Page 109 and 110:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 C
Page 111 and 112:
S-12 subroutine vec_mult(p1,v3,v4,N
Page 113 and 114:
S-12 do i=1,N S-13 p(i) = v1(i) * v
Page 115 and 116:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 117 and 118:
Fortran 1 Example target_unstructur
Page 119 and 120:
S-19 p[i] = p[i] + (v1[i] * v2[i]);
Page 121 and 122:
Fortran 1 Example target_update.2.f
Page 123 and 124:
Fortran 1 2 3 4 5 6 7 Example decla
Page 125 and 126:
1 2 3 4 5 6 7 implicit device data
Page 127 and 128:
Fortran 1 Example declare_target.4.
Page 129 and 130:
Fortran 1 Example declare_target.5.
Page 131 and 132:
S-27 #pragma omp parallel for S-28
Page 133 and 134:
1 2 3 4 5 6 7 8 9 10 11 4.6 teams C
Page 135 and 136:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 137 and 138:
1 2 Example teams.3.c C / C++ S-1 f
Page 139 and 140:
Fortran 1 Example teams.4.f90 S-1 m
Page 141 and 142:
1 2 3 4 5 6 7 8 9 4.6.6 target team
Page 143 and 144:
1 2 3 4 5 6 C / C++ The Fortran ver
Page 145 and 146:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 147 and 148:
1 2 Example async_target.3.c C / C+
Page 149 and 150:
1 2 Example async_target.4.c C / C+
Page 151 and 152:
1 2 3 4 5 6 7 8 9 4.8 Array Section
Page 153 and 154:
1 2 3 4 Example array_sections.3.c
Page 155 and 156:
1 2 3 4 5 6 4.9 Device Routines 4.9
Page 157 and 158:
1 2 3 4 5 4.9.2 omp_get_num_devices
Page 159 and 160:
1 2 3 4 5 6 7 8 9 10 11 12 4.9.4 Ta
Page 161 and 162:
1 CHAPTER 5 2 SIMD 3 4 5 6 7 8 9 10
Page 163 and 164:
Fortran 1 2 3 4 5 6 7 8 9 10 11 12
Page 165 and 166:
S-9 end do S-10 call work(a, b, N )
Page 167 and 168:
1 2 3 4 5 6 Example SIMD.4.c C / C+
Page 169 and 170:
1 2 Example SIMD.6.c C / C++ S-1 #p
Page 171 and 172:
1 2 Example SIMD.7.c C / C++ S-1 #i
Page 173 and 174:
1 Example SIMD.8.c C / C++ S-1 #inc
Page 175 and 176:
S-43 print 2, "passed", pri S-44 el
Page 177 and 178:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 Th
Page 179 and 180:
S-12 S-13 !$OMP CRITICAL(YAXIS) S-1
Page 181 and 182:
1 2 3 4 5 6 7 8 9 10 6.2 Worksharin
Page 183 and 184:
1 2 3 4 5 6 7 8 9 10 11 6.3 Binding
Page 185 and 186:
1 2 3 4 5 6 7 8 9 6.4 The atomic Co
Page 187 and 188:
S-37 S-38 DO I = 1,1000 S-39 X(I) =
Page 189 and 190:
S-14 * Use fetch_and_add to impleme
Page 191 and 192:
1 2 3 4 6.5 Restrictions on the ato
Page 193 and 194:
S-15 !$OMP ATOMIC UPDATE S-16 I = I
Page 195 and 196:
S-40 /* because they were not acces
Page 197 and 198:
1 2 3 4 5 6.7 The ordered Clause an
Page 199 and 200:
Fortran 1 2 3 4 Example ordered.2.f
Page 201 and 202:
1 2 3 4 5 6 7 8 9 10 11 12 13 6.8 D
Page 203 and 204:
S-14 A[i][j] = foo(i, j); S-15 S-16
Page 205 and 206:
S-16 p(k,j,i) = (tmp1 + tmp2 + tmp3
Page 207 and 208:
1 2 6.9 Lock Routines This section
Page 209 and 210:
Fortran 1 2 3 4 5 6 7 8 9 10 11 12
Page 211 and 212:
1 2 Example simple_lock.1.c C / C++
Page 213 and 214:
1 2 3 4 6.9.5 Nestable Lock Routine
Page 215 and 216:
S-43 SUBROUTINE NESTLOCK(P) S-44 US
Page 217 and 218:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 219 and 220:
1 2 3 4 5 6 The following example d
Page 221 and 222:
Fortran (cont.) S-11 !$OMP END PARA
Page 223 and 224:
1 2 3 4 5 6 7 S-25 END PROGRAM INC_
Page 225 and 226:
Fortran 1 Example default_none.1.f
Page 227 and 228:
Fortran 1 2 3 4 5 Example private.1
Page 229 and 230:
1 S-10 for (i=0; i
Page 231 and 232:
S-19 !$OMP END SINGLE S-20 !$OMP EN
Page 233 and 234:
Fortran (cont.) 1 2 3 4 5 6 7 The f
Page 235 and 236:
Fortran (cont.) S-1 PROGRAM PRIV_RE
Page 237 and 238:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 239 and 240:
1 2 3 4 5 6 7.8 The lastprivate Cla
Page 241 and 242:
1 2 3 S-16 END DO S-17 S-18 END SUB
Page 243 and 244:
Fortran (cont.) S-10 S-11 END PROGR
Page 245 and 246:
Fortran 1 2 3 4 5 6 7 Example reduc
Page 247 and 248:
1 2 3 4 5 7.10 The copyin Clause Th
Page 249 and 250:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 251 and 252:
1 2 3 4 S-11 S-12 !$OMP BARRIER S-1
Page 253 and 254:
1 2 3 4 5 6 7 8 9 10 7.12 C++ Refer
Page 255 and 256:
S-1 program example S-2 integer ::
Page 257 and 258:
1 2 3 4 5 6 7 8 9 8.1 The OpenMP Me
Page 259 and 260:
1 Example mem_model.2.c C / C++ S-1
Page 261 and 262:
1 Example mem_model.3.c C / C++ S-1
Page 263 and 264:
1 2 8.2 Race Conditions Caused by I
Page 265 and 266:
1 2 3 4 5 6 CONTROL VARIABLES Inter
Page 267 and 268:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 269 and 270:
Fortran 1 Example icv.1.f S-1 progr
Page 271 and 272:
Fortran 1 Example standalone.1.f90
Page 273 and 274:
1 Example standalone.2.f90 S-1 SUBR
Page 275 and 276:
S-34 #pragma omp barrier S-35 phase
Page 277 and 278:
S-35 #pragma omp taskwait S-36 } S-
Page 279 and 280:
1 2 3 4 5 9.5 Nested Loop Construct
Page 281 and 282:
Fortran 1 Example nested_loop.2.f S
Page 283 and 284:
Fortran 1 2 3 The following orphane
Page 285 and 286:
1 2 3 4 5 Example nesting_restrict.
Page 287 and 288:
1 2 Example nesting_restrict.6.c C
Page 289 and 290:
1 2 3 4 5 A.2 Changes from 4.0.1 to
show all

OpenMP Application Programming Interface Examples

Create successful ePaper yourself

Delete template?

Save as template?