A Brief Introduction to Fortran 77 - Polaris

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6.2 The PARALLEL directiveThe parallel/end parallel directive pair defines aparallel region and constitutes as parallel construct.An OpenMP program begins execution as a single task, calledthe master thread. When a parallel construct is encountered,the master thread creates a team of threads. The statementsenclosed by the parallel construct, including routines calledfrom within the enclosed construct, are executed in parallel byeach thread in the team.At the end of the parallel construct the threads in the teamsynchronize and only the master thread continues execution.The general form of this construct is:C$omp parallel [parallel-clause[[,]parallel-clause] ...]parallel regionC$omp end parallelThere are several classes of parallel-clauses. Next, we discussthe private(list)clause.© 1998 David A. Padua44 of 118
All variables are assumed <strong>to</strong> be shared by all tasks executingthe parallel region. However, there will be a separate copy ofeach variable listed in a private clause for each task. Therewill also be an additional copy of the variable that can beaccessed outside the parallel region.Variables defined as private are undefined for the threadentering the construct and are also undefined for the thread onexit from a parallel construct.© 1998 David A. Padua45 of 118
Page 1 and 2: A Brief Introduction to Fortran 771
Page 3 and 4: InterpretersAn interpreter is a pro
Page 5 and 6: Source formTraditionally, Fortran s
Page 7 and 8: Lower case letters are considered e
Page 9 and 10: The form of a character constant is
Page 11 and 12: A scalar variable does not have to
Page 13 and 14: ExpressionsExpressions in Fortran c
Page 15 and 16: The logical operators are:.NOT. Log
Page 17 and 18: 3. DO statement. Iterative statemen
Page 19 and 20: Program UnitsA Fortran program alwa
Page 21 and 22: Notice that the variable y in the l
Page 23 and 24: Each read starts on the next record
Page 25 and 26: function rtflsp(func,x1,x2,xacc)par
Page 27 and 28: A Brief Introduction to Fortran 90
Page 29 and 30: IMPLICIT none29 of 118
Page 31 and 32: Array Shapes and SizesThe shape of
Page 33 and 34: Fortran 90 Intrinsic Proceduresaint
Page 35 and 36: Finer control on when an array is c
Page 37 and 38: Procedure InterfacesWhen a procedur
Page 39 and 40: Expressions in Fortran 90 may conta
Page 41 and 42: In the following compound statement
Page 43: 6.1 IntroductionOpenMP is a collect
Page 47 and 48: Notice that the first statement can
Page 49 and 50: 6.4 The PSINGLE directiveFinally, s
Page 51 and 52: A better example of psingle:c$ompc$
Page 53 and 54: The syntax of the pdo directive is
Page 55 and 56: 6.6 The PARALLEL DO directiveAn alt
Page 57 and 58: And the routine pdo_2 can be rewrit
Page 59 and 60: 6.7 The PSECTIONS directiveAn alter
Page 61 and 62: end© 1998 David A. Padua61 of 118
Page 63 and 64: Chapter 7. Parallel Loops in OpenMP
Page 65 and 66: Chapter 6. OpenMP65 of 118
Page 67 and 68: Another example of a race is:c$omp
Page 69 and 70: Another example is:c$ompparallel do
Page 71 and 72: 7.2 Race-free parallel loopsNext, w
Page 73 and 74: 7.3 PrivatizationSometimes the tran
Page 75 and 76: Sometimes it is necessary to privat
Page 77 and 78: One way to solve this problem is to
Page 79 and 80: Variables in lastprivate are privat
Page 81 and 82: print *,a(1),a(2)endprints1.000000
Page 83 and 84: To account for this, a and b should
Page 86 and 87: Most induction variables are quite
Page 88 and 89: Here, again, only the induction var
Page 90 and 91: The way to remove the races produce
Page 92 and 93: We can now proceed as above to obta
Page 94 and 95:
However, there is a way to improve
Page 96 and 97:
Notice that now no races exist beca
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7.6 Execution time of a parallel do
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following time lines:abcdeDabcdeDDa
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7.6 Critical Regions and Reductions
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Here, we use the critical directive
Page 106 and 107:
The assumption is that it does not
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© 1998 David A. Padua108 of 118
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