I have been using Armadillo 4.2 version (from linux mint package manager) for quite a some time. That version had no problem when compiled with icc, and codes compiled with icc ran very fast (about 10%-15% fast compared to g++).
Recently I have upgraded Armadillo to recent 6.1 version (from the official website). But in this case, all the codes compiled correctly with icc, but gave runtime error.
error: eig_sym(): failed to converge
terminate called after throwing an instance of 'std::runtime_error'
what(): eig_sym(): failed to converge
Aborted
Codes compiled correctly with g++ ran perfectly.
I have also tried previous 5.6 version, but the same problem.
Any solutions?? I had to revert back to old 4.2 version to get that extra speed from icc...
The Intel C++ compiler is known to contain of bugs when dealing with heavily templated libraries like Armadillo (see for example here and here).
You can increase the performance of gcc compiled code by enabling auto-vectorization (using -O3) and using the native machine instruction set (using -march=native). For example:
g++ code.cpp -o code -O3 -march=native -larmadillo
Also make sure that the matrix you're passing to eig_sym() is actually symmetric.
Related
I have a project written in c++ that I compile locally using g++ version 4.8.4 with following code
g++ BasicModel.cpp -std=c++11x -O3
I am trying to submit this file to a cluster to run large numbers of parallel simulations and to do this i need to compile the code on the cluster. g++ compiler on the cluster is out of data so i'm forced to use ICC compiler version 13.0.0
when run with the following
ICC BasicModel.cpp -O3
This however does not recognise lots of the c++11 syntax i've used. Are their flags i could use to avoid this or do i need to rewrite my code?
-std=c++11x is wrong it should be -std=c++11.
I recently updated Ubuntu from 15.04 to 15.10. One of the major differences between these versions is the update of the default gcc version from gcc-4.9 -> gcc-5. The library I'm developing has been written and compiled for gcc-4.9, and relies on other libraries which only work in gcc-4.9.
I have installed gcc-4.9 onto my computer, and I can successfully compile both the library and my source file. However, when I tried to run the resultant program I get this error:
terminate called after throwing an instance of 'std::ios_base::failure[abi:cxx11]'
what(): basic_ios::clear: iostream error
Aborted (core dumped)`
The source code, and the file I'm trying to read here used to work before the upgrade. I have tried using the -D_GLIBCXX_USE_CXX11_ABI=0 flag, but I'm not sure this is the right thing to do, also it doesn't work.
This is an example of the flags I'm currently including in my makefile:
CPPFLAGS = -O0 -g3 -Wall -c -fpermissive -D_GLIBCXX_USE_CXX11_ABI=0 -std=c++0x -fPIC -MMD -MP
Any ideas that might help me out?
You "simply" need to recompile everything your program needs that is C++.
See eg the Debian wiki on the transision which has (inter alia)
The good news is, that GCC 5 now provides a stable libcxx11 ABI, and stable support for C++11 (GCC version before 5 called this supported experimental). This required some changes in the libstdc++ ABI, and now libstdc++6 provides a dual ABI, the classic libcxx98 ABI, and the new libcxx11 (GCC 5 (<< 5.1.1-20) only provides the classic libcxx98 ABI). The bad news is that the (experimental) C++11 support in the classic libcxx98 ABI and the new stable libcxx11 ABIs are not compatible, and upstream doesn't provide an upgrade path except for rebuilding
There is no shortcut.
I got my self an ARM based development board (NVIDIA Jetson K1).
The thing is already equipped with Ubuntu system. I was able to use gcc 4.8 directly on the device, but it doesn't contain g++. Installing g++ with apt-get as usual wouldn't work because nobody ever bothered to maintain a complete ppa supporting ARM architecture.
Now I tried to compile the latest GCC manually. Everything went smooth when I compile and installed the requirements (MPC, MPFR, GMP). But I failed building GCC itself, and found out that the mad error in config.log telling me that a working C++ compiler can not be found.
I believe there must be a way to get a working g++ compiler working on the device itself rather than having to cross compile. Does anyone have a clue on how this can be done?
The message is right. GCC 4.8 is written in C++ so it needs to be compiled with a C++ (cross) compiler.
So here's the situation: I need to be able to compile binaries from a Linux machine (on Ubuntu, for what it's worth) which are able to run from a SPARC server. The program I'm trying to compile is very simple:
#include <stdio.h>
#include <stdlib.h>
int main() {
printf("Testing the SPARC program...");
return EXIT_SUCCESS;
}
I've tried a number of different compile lines to get it to work, but unfortunately nothing appears to be working.
I tried the traditional:
clang -target sparc blah.c -o blahsparc
But this doesn't work, with a bunch of assembler failures:
/tmp/blah-519e77.s: Assembler messages:
/tmp/blah-519e77.s:7: Error: unknown pseudo-op: '.register'
/tmp/blah-519e77.s:8: Error: unknown pseudo-op: '.register'
/tmp/blah-519e77.s:9: Error: unknown pseudo-op: '.register'
/tmp/blah-519e77.s:10: Error: unknown pseudo-op: '.register'
/tmp/blah-519e77.s:11: Error: no such instruction: 'save %sp,-240,%sp'
/tmp/blah-519e77.s:12: Error: no such instruction: 'st %g0, [%fp+2043]'
...
clang: error: assembler (via gcc) command failed with exit code 1 (use -v to see invocation)
I've tried this also:
clang -cc1 -triple "sparc-unknown-Linux" blah.c -o blahsparc
which complains about the missing headers, so instead of using -cc1, I use -Xclang:
clang -Xclang -triple -Xclang "sparc-unknown-Linux" blah.c -o blahsparc
however, this also fails due to "error: unknown target CPU 'x86-64'".
I'm not sure where to proceed with this. I've tried using crosstool-ng as well with very little success.
As of the 3.4.2 release (June 2014), llvm is missing code necessary to be able to generate object files for sparc targets. Older releases (1.x & 2.x) had support for it, but llvm's framework for emitting object files was less mature back then. When the current framework was rolled out it looks like they didn't migrate all platforms.
The documentation seems to imply that a combination of llvm/gcc is known to work, but I think that table was tabulated based on a much earlier version of llvm when they had a less mature framework for emitting object files.
Support for emitting object files was added to their SVN trunk in revision r198533 (this thread discusses the commit), but as you can see in the 3.4.2 final release, files & changes added in r198533 aren't present.
As an aside, clang currently isn't functional in sparc solaris (not sure about sparc in general). The parser seems to have trouble parsing templates; I get coredumps & the like. I ran across a thread a week or so ago discussing alignment problems in sparc/solaris clang, and this may be one of the reasons clang isn't yet usable on this platform.
If you need a cross compiler for Sparc that runs on an Ubuntu machine, the simplest way I know of is to use Buildroot. Here's a small tutorial on how to obtain a cross compiler and test the generated executables on a Sparc emulator.
LLVM 3.6.2 has some support for sparc now... I was able to build llvm 3.6.2 and clang 3.6.2-r100 on my T2000. I haven't gotten C++ support working but I have built moderately complex C applications like htop.
I did compile LLVM using gcc 5.2 however I lower version should work as well although I'd suggested at least gcc 4.9 and no lower than gcc 4.7.
The LLVM emerge on gentoo crashed during the compile but I was able to resume it by moving to the portage directory with the llvm ebuilds and restarting the build manually:
cd /usr/portage/*/llvm/
ebuild llvm-3.6.2.ebuild merge
I had to override some of the default compiler:
CC="clang -target sparc-unknown-linux-gnu"
CXX="clang++ -target sparc-unknown-linux-gnu"
CFLAGS="-O2 -pipe"
CXXFLAGS="${CFLAGS}"
I don't know if you will be able to use this to build from an x86 machine... though clang is supposed to be able to do that. But worst case you might be able to get this going in qemu-system-sparc64 vm or on some real hardware that you can find cheap on ebay (T5xxx hardware is coming down in price and blades are dirt cheap)
I recently updated to clang 3.8 (which is as yet unreleased) and I was able to compile a c++ application by passing -lstdc++ in addition to the options above. I believe this is the same behavior as gcc when invoked as gcc rather than g++.
I've been trying to compile a multithread hello-world program under Cygwin using the newly introduced C++ 11 std::thread feature without success. I compiled and installed GCC 4.7.2 by myself, and the same code works without any problems under Linux with the same version of GCC. The first error I got was that the compiler did not recognize the -pthread flag. After researching on it for a while I noticed someone said on Cygwin this flag should be -lthread. I made the change and that error was gone, but another series of errors occur telling me thread is not member of std. I wonder if it's caused by the wrong configuration of the compiler during installation, or std::thread is simply not supported under Cygwin?
This looks like you did not compile the program with the appropriate standard library flag. If you want to compile for C++11 you should use:
g++ --std=c++0x -o ...
The --std flag sets the appropriate language compatibility level. If this does not help, please post the error messages you got as a source listing.