OpenMP® Forum

For C/C++ min/max reduction operators with list items of type float, double, or long double, what should the initial values of the private copies be? E.g., for a min reduction, the initial value of the private copy should be the "largest representable value in the reduction list item type" (OpenMP 3...

Arguments to printf() are subject to default argument promotions, which, for a type _Bool argument, results in an integer promotion; specifically, it will be converted to an int before being printed---the C11 standard states on pp. 50-51: The rank of _Bool shall be less than the rank of all other st...

The OpenMP 3.1 API spec states on p. 104, l. 1, that the private copy of a list item in a reduction clause is initialized as follows for min and max operators: max Least representable value in the reduction list item type min Largest representable value in the reduction list item type How should the...

That explains it. Thanks, Mark!

The Fortran-specific part of Section 2.9.1.2 ( Data-sharing Attribute Rules for Variables Referenced in a Region but not in a Construct ) of the OpenMP 3.1 spec doesn't explicitly address variables declared in a main program and accessed by host association in an internal subprogram. Two questions: ...

There's a data race in Examples A.15.13c and A.15.13f from the OpenMP 3.1 spec. Consider the following program that implements bin_search() from Example A_15_13.c, where, to more easily illustrate the problem, the LIMIT macro has been modified so that all generated tasks are final tasks: // A_15_13....

The resulting values of the x and y arrays are different between examples A.22.1c and A.22.1f. It's probably no big deal, as the OpenMP concepts are implemented correctly, though it could result in some confusion for someone who attempts to run both programs and compare the results. The former examp...

I have a question regarding Example A.7. Lines 11-15 on p. 177 state: The call to the omp_set_dynamic routine with argument 0 in C/C++, or .FALSE. in Fortran, disables the dynamic adjustment of the number of threads in OpenMP implementations that support it. In this case, 10 threads are provided. No...

With respect to explicit tasks, there's already a stronger restriction on page 99, lines 25-26:

A list item that appears in a reduction clause of the innermost enclosing worksharing or parallel construct may not be accessed in an explicit task.

The OpenMP 3.0 API spec defines a "closely nested region" on p. 6, lines 1-2, as: A region nested inside another region with no parallel region nested between them. The "Non-conforming code" example involves task regions that are closely-nested in the parallel region with the reduction clause, while...