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atomicAdd — perform an atomic addition to a variable


int atomicAdd( inout int mem,
  int data);
uint atomicAdd( inout uint mem,
  uint data);



The variable to use as the target of the operation.


The data to be added to mem.


atomicAdd performs an atomic addition of data to the contents of mem and returns the original contents of mem from before the addition occured. The contents of the memory being updated by the atomic operation are guaranteed not to be modified by any other assignment or atomic memory function in any shader invocation between the time the original value is read and the time the new value is written.

Atomic memory functions are supported only for a limited set of variables. A shader will fail to compile if the value passed to the mem argument of an atomic memory function does not correspond to a buffer or shared variable. It is acceptable to pass an element of an array or a single component of a vector to the mem argument of an atomic memory function, as long as the underlying array or vector is a buffer or shared variable.

Version Support

OpenGL Shading Language Version
Function Name 1.10 1.20 1.30 1.40 1.50 3.30 4.00 4.10 4.20 4.30 4.40 4.50
atomicAdd - - - - - - - - -
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