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Short version: is this possible?
Long version: I have tried to use aligned allocators either directly or indirectly for a couple of different projects using the Xeon Phi, and have yet to be successful in compiling it x0 My understanding is that the allocator rules / parameters / syntax changed (again) similar to this issue:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51626
I distinctly remember finding a different bug talking about 4.7.0 vs 4.7.3 or something, but cannot seem to dig it up again. Anyway, my understanding of custom allocators is limited to say it nicely. I understand that I can alternatively use C-style arrays with _mm_malloc, but this is not what I desire. I desire the ability to use aligned allocators.
For example, trying to use something like this:
https://gist.github.com/gavrus/5986353
where the only difference is I added
#include <cstddef> // ptrdiff_t #include <stdexcept> // std::length_error #include <xmmintrin.h>// _mm_malloc
to allow it to compile in unix environments. The allocator works fine if I use things without the Phi's, but as soon as that ends up in an offload region it will fail. The example of that is rather verbose, so I elect to include a somewhat more standard example here instead using Eigen (which internally uses aligned allocators for their data types):
#include <iostream> #pragma offload_attribute(push, target(mic)) #include <Eigen/Core> #pragma offload_attribute(pop) int main(int argc, char **argv) { Eigen::Vector3f original(1,2,3); float *d = original.data();// just gives raw pointer std::cout << "Vec Before: " << std::endl << original << std::endl; #pragma offload target(mic:0) inout(d : length(3)) { Eigen::Vector3f test(5,6,7); d[0] = test.x(); d[1] = test.y(); d[2] = test.z(); } std::cout << "Vec After: " << std::endl << original << std::endl; return 0; }
to compile it for just the node, I can comment out the #pragma lines (and scope braces...) using:
icpc -std=c++11 -I eigen/ -o test eigen_test.cpp
(I just cloned eigen locally, but it is also installed via yum and pkg-config with that works too) and it will print
Vec Before: 1 2 3 Vec After: 5 6 7
as expected. Putting the #pragma and scope braces back in, the compiler freaks out (mostly because Eigen uses a bunch of fancy templates), but the root cause here is:
undefined reference to `__gnu_cxx::new_allocator<char>::new_allocator()'
I have tried many different things, from static linking to any compiler flags I can find that sound reasonable...
For reference:
~> g++ -print-file-name=libstdc++.a /opt/rh/devtoolset-3/root/usr/lib/gcc/x86_64-redhat-linux/4.9.2/libstdc++.a ~> g++ --version g++ (GCC) 4.9.2 20150212 (Red Hat 4.9.2-6)
and (as I believe is to be expected):
~> icpc -print-file-name=libstdc++.a /opt/rh/devtoolset-3/root/usr/lib/gcc/x86_64-redhat-linux/4.9.2/libstdc++.a ~>> icpc --version icpc (ICC) 15.0.3 20150407
The only other thing that seems relevant here is the following from the icpc man page:
-stdlib[=keyword] (M*X only) (M*X only) Lets you select the C++ library to be used for linking. Architecture Restrictions: Not available on Intel(R) 64 architecture targeting Intel(R) MIC Architecture
e.g. forbidding -stdlib=libstdc++.
I apologize for this dump of information! I've been searching on and off for a while now and would love to know if this can even be done, and if so how to do it ;) I understand that the Phi's are still actively being developed, but I couldn't find anywhere explicitly forbidding what I want to do.
Thanks for any help!
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