USQCD Propagator File Format Proposal
			    March 29, 2007
			DeTar, Edwards, Osborn


Currently we have two file formats on the table.

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A twelve-source propagator file:
(12 logical records)
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User file XML:

<?xml version=\"1.0\" encoding=\"UTF-8\"?>
   <usqcdPropFile>
      <version>1.0</version>             # prop file version
      <id>USQCD_DiracFermion_12</id>     # Propagator file format type
      <precision>32</precision>          # Precision of the binary data
      <info>                             
                     # Sub-collaboration discretion
      </info>
   </usqcdPropFile>

Note, the lattice dimensions are already encoded in the private file
XML and are available to the user.

We use the DeGrand-Rossi gamma matrix convention with the unimproved
sign for gamma_2.

For the subcollaboration info field it is recommended that there be at
least a detailed specification of the gauge field, details of gauge
fixing and smearing, values of the parameters describing the clover
action, and the parameters specifying the source.  The way these are
presented would be left to the subcollaborations.

Twelve logical records follow.  Each one gives the solution for a
particular choice of source color and spin.  The records are ordered
so source color varies most rapidly, and source spin least rapidly.
As usual with QIO, each logical record includes a user-created XML
string.

User record XML for each of 12 records:

<?xml version=\"1.0\" encoding=\"UTF-8\"?>
   <usqcdPropInfo>
      <version>1.0</version>             # prop file version
      <spin>  3 </spin>
      <color> 1 </color>
      <info>                      
                     # Sub-collaboration discretion
      </info>
   </usqcdPropInfo>

The binary data is bigendian and in lexicographic site order (same as
with the gauge field).  Within a given site we have only one Dirac
spinor.  It can be single precision or double.  The order of words is
as follows, going from least rapidly varying to most rapidly varying:

    sink spin
    sink color
    re/im

The user also provides a descriptive datatype label for the site word
order.  This label should be standard.  Here is a suggestion:

   USQCD_F3_DiracFermion
   USQCD_D3_DiracFermion

(The precision information repeats the information in the file XML,
and appears again with the designation "F" or "D" but they should all
be consistent.)

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The JLab propagator format (modified slightly to make more standard)
(1 logical record)
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User file XML:


<?xml version=\"1.0\" encoding=\"UTF-8\"?>
   <usqcdPropFile>
      <version>1.0</version>             # prop file version
      <id>LHPC_DiracPropagator</id>      # Propagator file format type
      <precision>32</precision>          # Precision of the binary data
      <info>                             
                     # Sub-collaboration discretion
      </info>
   </usqcdPropFile>


User record XML:

<?xml version=\"1.0\" encoding=\"UTF-8\"?>
   <usqcdPropInfo>
      <version>1.0</version>             # prop file version
      <info>                      
                     # Sub-collaboration discretion
      </info>
   </usqcdPropInfo>

As always the sites are arranged in lexicographic order and the byte
order is big endian.  The word order per site is the same as JLab
currently has it: from least rapidly varying to most rapidly, it is

  sink spin
  source spin
  sink color
  source color
  re/im

but the datatype name for this word order needs to be changed to
something more specific than "Lattice".  Suggestion:

   USQCD_F3_DiracPropagator
   USQCD_D3_DiracPropagator

Continue to use the precision flag "F" or "D".

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