the Espresso build system creates Cuda binaries for compute capability 1.1 as well as 2.0. Compute capability 1.1 does not allow for float atomic adds, so in this case we use a little workaround, which is slower than the native float atomic add present in later compute capabilities. You always get this warning message, unless you remove the "-gencode arch=compute_11,code=compute_11" from configure.ac
". Most likely it has no impact on your performance, since Cuda determines at runtime which executable to use (depending on the compute performance of your Cuda device). So unless you have some pretty old GPU, you will be using the 2.0 binary, which in turn makes use of the native atomic add for floats.