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GreenX Library - TimeFrequency

This library provides optimal quadrature grid points and weights for imaginary time-frequency transforms, commonly occurring in MP2, RPA and Green's function methods. Optimisation is performed with the Minimax procedure, minimising the maximum error of the quadrature. This typically results in an error that is more evenly distributed across the interval of interest. Grids are provided with n-points ranging from 6 to 34, and for different values of the transition energy ratios Rm (on average 15 R-values for each grid point).

For additional details, please refer to the corresponding JOSS paper, included here.

Building

With CMake, change to the GreenX root, then type:

mkdir build && cd build
cmake ../
make -j 
make install

Running the Tests

Application tests are run with the pytest framework. Having installed pygreenx (see the top-level README) change to <GX_ROOT>/<BUILD_DIR> and type ctest. Additionally, one can change to the test folder and explicitly run the pytest command from there:

cd <GX_ROOT>/<BUILD_DIR>/test/time-frequency
pytest -s 
# or
pytest -s test_name.py

Calling the MiniMax Library

Information on how to use the library is always up-to-date on the GreenX website.

For Developers

Adding a New Test

Write a test_name.py and test_name.f90 in test/. test_name.f90 should accept some input parameter/s, make a library call and write the result to file. test_name.py should provide the input parameters (the simplest way is to write to file), execute the binary built from test_name.f90, parse the result and make the assertions. This implies the reference results should also be stored in test_name.py.

test_name.py must include the fixture:

@pytest.fixture()
@pytest.mark.usefixtures("get_binary", "greenx_build_root")
def fortran_binary(get_binary, greenx_build_root):
    name = 'gx_tabulate_grids.exe'
    _binary = get_binary(name)
    assert _binary is not None, f'{name} cannot be found in {greenx_build_root}'
    print(f'Binary source: {_binary}')
    return _binary

where the binary name should be consistent with whatever the developer has called the binary in the CMakeLists.txt

One notes that the working directory for all tests is tmp_path, which is switched to using a fixture defined in GX-TimeFrequency/test/conftest.py, for the duration of the test execution. The tmp_path fixture will provide a temporary directory unique to the (py)test invocation, created in the base temporary directory.

A new test can be added to this CMakeLists.txt in the following way:

set(LIBS_FOR_TESTING)
list(APPEND LIBS_FOR_TESTING LibGXMiniMax)

set(TEST_NAME "test_gx_minimax_grid")
add_app_test(TEST_NAME TEST_TARGET_DIR LIBS_FOR_TESTING)

Calling add_app_test should ensure that the directory level structure in the build folder is consistent with example python driver. For multiple tests, one can place the call to add_app_test in a loop, and supply different test names.

All the tests can be run by switching to the build/ directory and typing ctest, however they can also be run in the test/ directory of the source by typing pytest -s as long as the 'ENV VAR' to the build directory has been defined:

export GX_BUILD_DIR=<path/2/build/>