Questions tagged [openacc]

The OpenACC Application Program Interface describes a collection of compiler directives to specify loops and regions of code in standard C, C++ and Fortran to be offloaded from a host CPU to an attached accelerator, providing portability across operating systems, host CPUs and accelerators.

The OpenACC Application Program Interface describes a collection of compiler directives to specify loops and regions of code in standard C, C++ and Fortran to be offloaded from a host CPU to an attached accelerator, providing portability across operating systems, host CPUs and accelerators.

Useful Links

The OpenACC directives and programming model allow programmers to create high-level host+accelerator programs without the need to explicitly initialize the accelerator, manage data or program transfers between the host and accelerator, or initiate accelerator startup and shutdown.

All of these details are implicit in the programming model and are managed by the OpenACC API-enabled compilers and runtimes. The programming model allows the programmer to augment information available to the compilers, including specification of data local to an accelerator, guidance on mapping of loops onto an accelerator, and similar performance-related details.

How to get Useful Answers to your OpenACC Questions on StackOverflow

Here are a number of suggestions to users new to OpenACC and/or StackOverflow. Follow these suggestions before asking your question and you are much more likely to get a satisfactory answer!

  • Search StackOverflow (and the web!) for similar questions before asking yours
  • Include an as-simple-as-possible code example in your question and you are much more likely to get a useful answer. If the code is short and self-contained (so users can test it themselves), that is even better.
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Restrictions of the OpenACC aware CAPS compiler

I'm currently writing a report on the state of automatic parallelisation techniques on compiler level. Concerning the OpenACC standard, several compilers are available, such as the PGI compiler, CAPS, or the CRAY compiler. However, I was wondering…
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open ACC : no output with PGI compiler

I'm undergraduate student who is studying open ACC in a internship. I made basic sample code myself for testing PGI workstation compiler(version 14.1) works well, and it worked with command line instruction 'pgcc -acc lab04.c -Minfo' But there is…
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Is possible to use CUBLAS with OpenACC?

I have to implement a function that I already have in CUDA-C using the OpenACC directives (I have to do a comparison). In the original code there's cubasSgemv call, there is some way to use cublas library under openacc?
Angantyr
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optimizing nbody on a GPU cluster with openacc

We are trying to provide a generic nbody algorithm for multiple Nodes. A node has 2 GPUs and 1 CPU. We want to calculate the n-body only on GPUs using openacc. After doing some research about openacc i am unsure how to spread the calculation to…
Käptn Freiversuch
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Nested data environment with different subparts of the same array

Here is my question about openacc. I read the APIs (v1 and v2), and the behavior of nested data environment with different subparts of the same array is unclear to me. Code example: #pragma acc data pcopyin(a[0:20]) { #pragma acc data…
chabachull
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Trouble parallelizing OpenACC loop

I have a old code written in FORTRAN and i need to accelerate it using OpenACC but when i try using directives, it says there is a dependance of un,vn,pn which prevents parallelism. Is it possible to parallelize this loop? I am new to OpenACC but…
Jovi DSilva
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Using struct datatype inside of OpenACC pragma line

I'm using the CAPS OpenACC compiler. I've tried to use dynamic array inside of the struct data type in the OpenACC pragma lines. My code like that: struct Structure{ int val[n]; int length; int *valdyn; }; #pragma acc…
grypp
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how to get the available memory on the device

I'm trying to obtain how much free memory I have on the device. To do this I call the cuda function cuMemGetInfo from a fortran code, but it returns negative values for the free amount of memory, so there's clearly something wrong. Does anyone know…
rosilho
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OpenACC error when running programs of higher magnitude

Using the following code, is it correct? I have 2GB Geforce 750M and using the PGI Fortran compiler. The program works fine for 4000x4000 arrays, anything higher it complains even though it should not, You can see i have allocated a 9000x9000 array…
Jovi DSilva
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Variables in module instead of common statement

I'm trying to accelerate a piece of code using cuda fortran. This code uses the common statement in the definition of the variables which is not valid in the device code with cuda. What I did is define the variables in a module instead of using the…
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Always does all lines inside openACC kernels work on GPU?

I wonder something related kernels structure. May not the every line inside kernels work on GPU? for example i have this code: #pragma acc kernels copy(a[0:n],b[0:n]) { #pragma acc loop for (i = 0; i < n; i++) a[i] =…
grypp
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openacc say Segmentation fault when split big data

As i have big data to malloc in GPU, i have to split it.Like follows, to split temp1 and temp2 from start to end once: for (int start = 0; start < total; start += step) { int end = start + step > total?total:start+step; fprintf(stderr,…
luxuia
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pcopyin after a create

I ask this question to be clear on the behaviour of these two clauses when in nested data environment. When I first read the openACC API, I thought that if I had the following code: #pragma acc create(a[0:20]) { #pragma acc pcopyin(a[0:20]) { …
chabachull
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openAcc how to profile

Hi I was using CAPS OpenACC compilers, but something strage happens when I try to get some preliminary profile results. At first, I ran the code with declaring HMPPRT_LOG_LEVEL="info", which generates some profile results with time stamp. [ …
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OpenAcc : How To parallelize the function calls

I am working on a project,i am trying to parallelize the application. there are some functions which i am trying to parallelize but the problem is these function call other functions very frequently.loops are only for computation and there are many…
amitj
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