vec_io/vec_io.html

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      VEC_IO - File I/O for Fixed Length Vectors
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      VEC_IO <br> File I/O for Fixed Length Vectors
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    <p>
      <b>VEC_IO</b>
      is a FORTRAN90 library which
      provides a simple interface to read or write a set of
      vectors to a file, which are of a single fixed size.  The vectors
      can be read or written in any order.  Several sets of files can
      be handled at one time.
    </p>

    <p>
      A common procedure computationally involves computing a state
      variable U(T,X,Y) at a fixed set of nodes, and for an increasing
      sequence of equally spaced times.  For certain optimization
      problems, this process is followed by a <i>backwards</i> computation,
      in which the data is analyzed in reverse order.
    </p>

    <p>
      Since the data U(T,X,Y) for a single time step may require a
      large amount of storage, and usually only two sets of data
      are needed at any point in the computation, namely the values
      at the current time, and at the future or previous time, it
      is convenient to store the solution data for each timestep
      in a single file.
    </p>

    <p>
      A simple use of <b>VEC_IO</b> allows the user to write each
      solution vector to the file in forward order, and then to
      read back the same solution data in reverse order.  Of course,
      more general access patterns are also available.
    </p>

    <p>
      At the moment, the only kind of data that can be written or
      read is a double precision vector of length <b>N</b>.
      Sets of this data can be stored in an unformatted direct access file,
      or a formatted direct access file.
    </p>

    <p>
      It would also be useful to allow other data types, such
      as single precision or integer data, and other file formats,
      but this has not yet been set up.
    </p>

    <h3 align = "center">
      Licensing:
    </h3>

    <p>
      The computer code and data files described and made available on this web page
      are distributed under
      <a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
    </p>

    <h3 align = "center">
      Related Data and Programs:
    </h3>

    <p>
      <a href = "../../f_src/cell/cell.html">
      CELL</a>,
      a FORTRAN90 library which
      defines a cell array, a generalization of an array which
      can compactly store and retrieve vector or matrix data of 
      varying size, such as the rows of a triangular matrix.
    </p>

    <p>
      <a href = "../../f_src/table_io/table_io.html">
      TABLE_IO</a>,
      a FORTRAN90 library which
      reads vector and table data
      from a file.  However, these routines read or write ALL the
      data in one operation, and only use the ASCII file format.
    </p>

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      Source Code:
    </h3>

    <p>
      <ul>
        <li>
          <a href = "vec_io.f90">vec_io.f90</a>, the source code.
        </li>
        <li>
          <a href = "vec_io.sh">vec_io.sh</a>,
          commands to compile the source code.
        </li>
      </ul>
    </p>

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      Examples and Tests:
    </h3>

    <p>
      <ul>
        <li>
          <a href = "vec_io_prb.f90">vec_io_prb.f90</a>,
          a sample calling program.
        </li>
        <li>
          <a href = "vec_io_prb.sh">vec_io_prb.sh</a>,
          commands to compile and run the sample program.
        </li>
        <li>
          <a href = "vec_io_prb_output.txt">vec_io_prb_output.txt</a>,
          the output from a run of the sample program.
        </li>
      </ul>
    </p>

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      List of Routines:
    </h3>

    <p>
      <ul>
        <li>
          <b>FILE_COPY</b> makes a copy of a file.
        </li>
        <li>
          <b>FILE_DELETE</b> deletes a named file if it exists.
        </li>
        <li>
          <b>FILE_EXIST</b> reports whether a file exists.
        </li>
        <li>
          <b>FILE_IS_OPEN</b> reports whether a file (specified by filename) is open.
        </li>
        <li>
          <b>FILE_RENAME</b> renames a file.
        </li>
        <li>
          <b>GET_UNIT</b> returns a free FORTRAN unit number.
        </li>
        <li>
          <b>R8AD_IO</b> reads or writes fixed size vectors, using R8AD protocol.
        </li>
        <li>
          <b>R8UD_IO</b> reads or writes fixed size vectors, using R8UD protocol.
        </li>
        <li>
          <b>TIMESTAMP</b> prints the current YMDHMS date as a time stamp.
        </li>
      </ul>
    </p>

    <p>
      You can go up one level to <a href = "../f_src.html">
      the FORTRAN90 source codes</a>.
    </p>

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    <i>
      Last revised on 05 October 2005.

    </i>

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