openmp

问题 This is the first time I am using OpenMP, and I apply it for Fortran. I happened to have a problem adjusting the loop where there is a variable that requires update from its previous value. I tried using PRIVATE clause but the result is far from those resulted by serial computation (without OpenMP). I looked somewhere in OpenMP website and I found one solution using !$OMP PARALLEL DO ORDERED which finally works (produce the same result with the serial one). But it seems that by using this,

问题 I have an openmp parallel loop in C++ in which all the threads access a shared array of double. Each thread writes only in its own partition of the array. Two threads cannot write on the same array entry. Each thread read on partitions written by the other threads. It does not matter if the data has been updated by the thread who owns the partition or not, as soon as the double is either the old or the updated value (not an invalid value resulting from reading a half-written double). Do I

问题 I'm trying to use omp in my C code and am having a problem: in the code i have #include but when i try to compile with: g++ -fopenmp -g -c parallel.c I get cc1plus: error: unrecognized command line option "fopenmp" and when i try: g++ -g -c parallel.c I get an error for both: omp.h: No such file or directory, and malloc not declared in this scope i tried with gcc with -fopenmp and get the same error. without the -fopenmp i still get the missing omp. 回答1: OpenMP is only supported in gcc 4.2

问题 I want to create one global array of objects (One object per possible thread spawned by OpenMP ) and reuse it throughout the program. Each thread will read its number using omp_get_thread_num and use it to index into the array. How can I get the maximum number of OpenMP threads that may be created during the whole execution of the program? The documentation of omp_get_max_threads says that this function is specified to return a value which is specific to the particular parallel region where

问题 PROBLEM : Long list of directives openmp fortran77 c$omp parallel default(shared) private(i,k,i1,i2,i3,i4,i5, $ i6,x0,y0,z0,vnx0,vny0,vnz0,qs0) c$omp do Task to be performed c$omp end do c$omp end parallel I'm trying to compile the above program using ifort and it works fine. I have checked with the serial version and I get the same result ifort -openmp -parallel -o ./solve But when I try to compile using gfortran it doesn't work. gfortran -fopenmp I get the following error quinckedrop.f:2341

问题 The program below crashes when I build it in Release x64 (all other configurations run fine). Am I doing it wrong or is it an OpenMP issue? Well-grounded workarounds are highly appreciated. To reproduce build a project (console application) with the code below. Build with /openmp and /GL and (/O1 or /O2 or /Ox) options in Release x64 configuration. That is OpenMP support and C++ optimization must be turned on. The resulting program should (should not) crash. #include <omp.h> #include <vector>

问题 I'm using modern fortran for doing parallel programming. I'm using vim and it's been really annoying me that the fortran.vim syntax files don't seem to handle compiler directives like !$omp or !dir$. These just get rendered as comments in vim so they don't stand out. In c/c++ these compiler directives are done using #pragma's so everything stands out like it were preprocessor code rather than comment code. So I want similar treatment in my fortran syntax. Here's an example of a multiline

问题 The current OpenMP standard says about the declare simd directive for C/C++: The use of a declare simd construct on a function enables the creation of SIMD versions of the associated function that can be used to process multiple arguments from a single invocation in a SIMD loop concurrently. More details are given in the chapter, but there seems to be no restriction there to the type of function the directive can be applied to. So my question is, can this directive be applied safely to an

问题 I would like to know how the task scheduling of the OpenMP task queue is performed. Here I read that, by default, OpenMP imposes a breadth-first scheduler and that they did some tests FIFO vs. LIFO, but they don't say anything about the default. Since I only have a single thread (I use the single directive) creating multiple tasks, I don't think it makes any sense comparing their breadth-first vs work-first scheduling. So, is the default FIFO or LIFO? And is it possible to change it? Thanks

问题 I have the following program: int main(){ double sum=0; #pragma omp parallel for reduction(+:sum) for(double x=0;x<10;x+=0.1) sum+=x*x; } When I compile it, I get the error invalid type for iteration variable ‘x’ . I take this to mean that I can only apply a parallel for construct to integer-based loops. But the internals of my loop really do depend on it being floating-point. Is there a way to convince OpenMP to do this? Is there a recommended alternative method? 回答1: From comments: No,