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# Compiler Flag Equivalence

The following table is an overview of some of the compiler flags that are equivalent or almost equivalent.

<table>
  <colgroup>
    <col />

    <col />

    <col />

    <col />
  </colgroup>

  <thead>
    <tr>
      <th>
        **Cray**
      </th>

      <th>
        **Intel**
      </th>

      <th>
        **GCC**
      </th>

      <th>
        **Explanation**
      </th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>
        default
      </td>

      <td>
        default
      </td>

      <td>
        `-O3 -ffast-math`
      </td>

      <td>
        Produce high level of optimization
      </td>
    </tr>

    <tr>
      <td>
        `-Oomp`

         (default)
      </td>

      <td>
        `-openmp`
      </td>

      <td>
        `-fopenmp`
      </td>

      <td>
        Activate OpenMP directives and pragmas in the code
      </td>
    </tr>

    <tr>
      <td>
        `-h byteswapio`
      </td>

      <td>
        `-convert big_endian`
      </td>

      <td>
        `-fconvert=swap`
      </td>

      <td>
        Read and write Fortran unformatted data files as big-endian
      </td>
    </tr>

    <tr>
      <td>
        `-f fixed`
      </td>

      <td>
        `-fixed`
      </td>

      <td>
        `-ffixed-form`
      </td>

      <td>
        Process Fortran source using fixed form specifications.
      </td>
    </tr>

    <tr>
      <td>
        `-f free`
      </td>

      <td>
        `-free`
      </td>

      <td>
        `-ffree-form`
      </td>

      <td>
        Process Fortran source using free form specifications.
      </td>
    </tr>

    <tr>
      <td>
        `-V`
      </td>

      <td>
        `--version`
      </td>

      <td>
        `--version`
      </td>

      <td>
        Dump version.
      </td>
    </tr>

    <tr>
      <td>
        `-h zero`
      </td>

      <td>
        N/A
      </td>

      <td>
        `-finit-local-zero`
      </td>

      <td>
        Zero fill all uninitialized variables.
      </td>
    </tr>

    <tr>
      <td>
        `-e m`
      </td>

      <td />

      <td />

      <td>
        Creates 

        `.mod`

         files to hold Fortran90 module information for future compiles.
      </td>
    </tr>

    <tr>
      <td>
        `-j`

         \<

        *dir_name*

        \>
      </td>

      <td />

      <td />

      <td>
        Specifies the directory <

        *dir_name*

        \> to which 

        `.mod`

         files are written when the 

        `-e m`

         option is specified
      </td>
    </tr>
  </tbody>
</table>