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I want to use floor/ceil functions of C in an OpenACC project. When I want to make an atomic update of a value.

#pragma acc atomic update
x=floor(x)+c

the compiler shows the following message:

PGCC-S-0155-Invalid atomic expression PGCC-S-0155-Invalid atomic region.

What could be the problem?

Constantinus Spanakis
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1 Answers1

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Atomic operations are for simple and straightforward operations like +, -, *, and /. If you take a look at the Section 2.12 (Atomic Construct) of the OpenACC Spec Page 42 [link], you will see the list of available operations to use in atomic construct.

So, although you could do floor on GPU, you cannot do it in atomic sections.

mgNobody
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