Edward Valeev - 2011-04-25

why use the libint compiler

The primary reason to use libint compiler is to generate custom Libint libraries. Most advanced customization, such as implementation of new integral types, recurrence relations, and computation strategies, will require making changes to the compiler. If you are interested in working on the compiler code please consider consulting with one of Libint authors, if possible, to avoid duplication of effort.

prerequisites

  1. Robust C++ compiler with "some" C++0x support. On a Mac, clang and icc both work with '-std=c++0x' flag;
  2. Recent boost library;
  3. Recent GMP library, including C++ support;
  4. (optional) Recent MPFR library for high-precision (>64bit) testing of the computed integrals;
  5. Standard GNU toolchain (make, tar, autoconf);
  6. doxygen and latex to make compiler documentation.
  7. Mercurial client.

getting the source code

The only way to get the compiler source is via the source code repository:
hg clone http://hg.code.sf.net/p/libint/mercurial libint-mercurial

compiling libint compiler

  1. enter the top source directory
  2. aclocal -I lib/autoconf
  3. autoconf
  4. make a separate directory where you will build the compiler (WARNING: BUILD DIRECTORY CANNOT BE LOCATED WITHIN THE SOURCE TREE), and enter that directory
  5. pick the appropriate configure command-line options (see the next section for more info). All available options can be listed as such: [libint_srcdir]/configure --help. Some information can be passed to configure via standard environmental variables:
    1. CPPFLAGS can be used if boost library is not in the default compiler search path: configure CPPFLAGS='-I/path/to/boost'
    2. CXX can be used to specify the C++ compiler to be used: configure CXX='clang++'
    3. CXXFLAGS can be used to specify the C++ compiler flags: configure CXXFLAGS='-std=c++0x'
  6. run configure

configuring libint compiler

These are the most useful configure options:

  • --enable-eri=N Use this option to enable support for N-th order
    derivatives of (4-center) electron repulsion integrals. To disable support for ERIs set N to 'no', or use the --disable-eri option. By default, N=0 (i.e. no derivatives are requested).
  • --enable-eri3=N Same as --enable-eri, except for 3-center ERIs.
  • --enable-eri2=N Same as --enable-eri, except for 2-center ERIs.
  • --with-max-am=L Speci es the maximum angular momentum
    level for the Gaussian basis functions when computing electron repul-
    sion integrals. By default, integrals over g-type functions (L=4) are
    supported.
  • --with-cartgauss-ordering=ORDER Specifies the ordering of cartesian Gaussians in shells. The known values are:
    • standard (default) standard ordering (xxx, xxy, xxz, xyy, xyz, xzz, yyy, ...)
    • intv3 -- intv3 ordering (yyy, yyz, yzz, zzz, xyy, xyz, xzz, xxy, xxz, xxx)
    • gamess -- GAMESS ordering (xxx, yyy, zzz, xxy, xxz, yyx, yyz, zzx, zzy, xyz)
    • orca -- ORCA ordering (hydrid between GAMESS and standard)
  • --with-shell-set=SET The library will support computation of shell sets sets subject to these restrictions:
    • standard -- standard ordering (default). For (ab|cd): l(a) >= l(b), l(c) >= l(d), l(a)+l(b) <= l(c)+l(d). For (b|cd): l(c) >= l(d).
    • orca -- ORCA ordering. For (ab|cd): l(a) <= l(b), l(c) <= l(d), l(a) < l(c) || (l(a) == l(c) && l(b) < l(d)). For (b|cd): l(c) <= l(d).

generating libint library

this will produce a tarball of libint library that is suitable for independent distribution (it will have its own configure, etc.):
1. make export

compiling libint library

Compilation of the generated library is straightforward:
1. Unpack the library: tar -xvzf libint-2.0.0-stable.tgz
2. cd libint-2.0.0-stable
3. ./configure --prefix=.... CXX=... CXXFLAGS=....
4. make
5. make install

It is very important to use the C++ compiler and compiler options that are appropriate for the given platform. It is impossible to provide specific recommendations for specific platforms. We recommend to use a vendor compiler (e.g., Intel) before trying clang++ and g++. In some situations, however, clang++ and g++ are known to outperform the x86 vendor compiler, so we recommend trying several compilers.

Other important configure flags are described in the next section.

libint library configure options

Besides --prefix and CXX and CXXFLAGS, the following configure options may be necessary/useful:

  • --with-real-type=TYPE specifies the data type used by the library. The default is "double" (double-precision floating-point real). The following values are also valid:
    • "float" -- single-precision floating-point number;
    • "libint2::simd::VectorSSEDouble" -- vector of 2 packed doubles that can be used with SSE2 instructions available on all x86 platforms;
    • "libint2::simd::VectorSSEFloat" -- vector of 4 packed floats that can be used with SSE instructions available on all x86 platforms;
    • "libint2::simd::VectorAVXDouble" -- vector of 4 packed doubles that can be used with AVX instructions available on recent x86 hardware (Intel Sandy Bridge and AMD Bulldozer);
    • "libint2::simd::VectorQPXDouble" -- vector of 4 packed doubles that can be used with QPX instructions available on recent PowerPC hardware (IBM Blue Gene/Q);
    • "libint2::simd::VectorFP2Double" -- vector of 2 packed doubles that can be used with FP2 (Double Hummer) instructions available on older PowerPC hardware (IBM Blue Gene/P).

N.B. When SIMD data types are used by Libint, integral sets will be computed in sets of 2 (4). To activate support SIMD it may be necessary provide additional compiler flags -- please refer to your compiler documentation.

using libint library

refer to Libint Programmer's Manual for (brief) information on how to use the library in your code.

 

Last edit: Edward Valeev 2012-08-27