Gaugefield

The Gaugefield class provides a template who has data member _lattice to store the gauge links for all the sites on a 4D lattice. Each link is an SU\((\)3\()\) matrix of data type SU3. One could use the indexer GIndexer<All, HaloDepth> to reach any link, including those in the halo. There are also several function members

• one();

• random(uint4* rand_state);

• gauss(uint4* rand_state);

initiating the gauge links to some special numbers like unity, random numbers or Gaussian algebra elements. Function swap_memory(Gaugefield<floatT, onDevice, HaloDepth,comp> &gauge) could swap two gauge fields _lattice and gauge. Since the gauge links _lattice are protected, one can only visit them via getAccessor(). Gaugefield also provides overloading for =, so that one could easily copy one gauge field to another. And the gauge links should always be unitary, so a su3latunitarize function is given.

Besides all the functions mentioned above, there are a bunch of convenient iterators with which one could perform operations on each of the link considered:

    * void iterateOverFullAllMu(Functor op); //perform "op" on all links including those in the halo in all 4 (spacetime) directions.

    * deviceStream<onDevice> iterateOverBulkAllMu(Functor op, bool useStream = false); //perform "op" on all links excluding those in the halo in all 4 (spacetime) directions.

    * void iterateOverFullLoopMu(Functor op); //perform "op" on all links including those in the halo for the first "Nloops" (default 4) directions.

    * void iterateOverBulkLoopMu(Functor op); //perform "op" on all links excluding those in the halo for the first "Nloops" (default 4) directions.

    * void iterateOverFullAtMu(Functor op);  //perform "op" on all links including those in the halo in a specific direction "Mu".

    * void iterateOverBulkAtMu(Functor op); //perform "op" on all links excluding those in the halo in a specific direction "Mu".

    * void iterateWithConst(Object ob); //set all links including those in the halo in all 4 (spacetime) directions to a constant value "ob".

Reading and writing Gaugefields

Usually before or after a lattice calculation one needs to read in or write out the gauge fields from/to a file, and this can be done by the readconf_* and writeconf_* function members of this template.

Reading/writing NERSC configurations to/from Gaugefield objects gauge can be accomplished with

gauge.readconf_nersc("path/to/gaugefile");
gauge.writeconf_nersc("path/to/gaugefile", rows = 2, diskprec = 1, endianness = ENDIAN_BIG);

One can set either rows to 2 or 3, depending on whether one wants compressed configurations. If one stores a compressed configuration, the NERSC reader calculates the third row of each SU(3) link automatically. The precision diskprec can be 1 for float or 2 for double.

Reading/writing ILDG configurations to/from Gaugefield objects gauge can be accomplished with

gauge.readconf_ildg("path/to/gaugefile");
gauge.writeconf_ildg("path/to/gaugefile", diskprec = 1);

In the case of ILDG configurations, the endianness is fixed to BIG and they are not compressed by definition, so these are not options that can be passed.

Reading a MILC configuration to a Gaugefield object gauge is done with

gauge.readconf_milc("path/to/gaugefile");

There is no MILC writer.

Reading an openQCD configuration to a Gaugefield object gauge is done with

gauge.readconf_openqcd("path/to/gaugefile");

There is no openQCD writer.

To learn more about the various configuration formats, look here.