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<div id="org-div-home-and-up">
 <a accesskey="h" href=""> UP </a>
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 <a accesskey="H" href="index.html"> HOME </a>
</div><div id="content" class="content">
<h1 class="title">Examples</h1>
<div id="table-of-contents" role="doc-toc">
<h2>Table of Contents</h2>
<div id="text-table-of-contents" role="doc-toc">
<ul>
<li><a href="#org9cde810">1. Accessing sparse quantities (integrals)</a>
<ul>
<li><a href="#org07e3407">1.1. Fortran</a>
<ul>
<li><a href="#org29b6380">1.1.1. Declare Temporary variables</a></li>
<li><a href="#org4f6ee33">1.1.2. Obtain the name of the TREXIO file from the command line, and open it for reading</a></li>
<li><a href="#orgce13fac">1.1.3. Read the nuclear repulsion energy</a></li>
<li><a href="#org156e32c">1.1.4. Read the number of molecular orbitals</a></li>
<li><a href="#orgad093f3">1.1.5. Allocate memory</a></li>
<li><a href="#org3283c85">1.1.6. Read one-electron quantities</a></li>
<li><a href="#orgcd6481c">1.1.7. Read two-electron quantities</a>
<ul>
<li><a href="#org5d1e8d1">1.1.7.1. Electron repulsion integrals</a></li>
<li><a href="#orgf49354f">1.1.7.2. Reduced density matrix</a></li>
</ul>
</li>
<li><a href="#orgcf80f54">1.1.8. Compute the energy</a></li>
<li><a href="#org27007da">1.1.9. Terminate</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#org861bef9">2. Reading determinants</a>
<ul>
<li><a href="#org8ca1578">2.1. Fortran</a></li>
</ul>
</li>
</ul>
</div>
</div>


<div id="outline-container-org9cde810" class="outline-2">
<h2 id="org9cde810"><span class="section-number-2">1.</span> Accessing sparse quantities (integrals)</h2>
<div class="outline-text-2" id="text-1">
</div>
<div id="outline-container-org07e3407" class="outline-3">
<h3 id="org07e3407"><span class="section-number-3">1.1.</span> Fortran</h3>
<div class="outline-text-3" id="text-1-1">
<div class="org-src-container">
<pre class="src src-f90"><span style="color: #a020f0;">program</span> <span style="color: #0000ff;">print_energy</span>
  <span style="color: #a020f0;">use</span> <span style="color: #0000ff;">trexio</span>
  <span style="color: #a020f0;">implicit</span> <span style="color: #228b22;">none</span>

  <span style="color: #228b22;">character</span>*(128)  ::<span style="color: #a0522d;"> filename   </span>! <span style="color: #b22222;">Name of the input file</span>
  <span style="color: #228b22;">integer</span>          ::<span style="color: #a0522d;"> rc         </span>! <span style="color: #b22222;">Return code for error checking</span>
  <span style="color: #228b22;">integer</span>(8)       ::<span style="color: #a0522d;"> f          </span>! <span style="color: #b22222;">TREXIO file handle</span>
  <span style="color: #228b22;">character</span>*(128)  ::<span style="color: #a0522d;"> err_msg    </span>! <span style="color: #b22222;">Error message</span>
</pre>
</div>

<p>
This program computes the energy as:
</p>

<p>
\[
   E = E_{\text{NN}} + \sum_{ij} \gamma_{ij}\, \langle j | h | i \rangle\,
   +\, \frac{1}{2} \sum_{ijkl} \Gamma_{ijkl}\, \langle k l | i j
   \rangle\; \textrm{ with } \; 0 < i,j,k,l \le n
   \]
One needs to read from the TREXIO file:
</p>

<dl class="org-dl">
<dt>\(n\)</dt><dd>The number of molecular orbitals</dd>
<dt>\(E_{\text{NN}}\)</dt><dd>The nuclear repulsion energy</dd>
<dt>\(\gamma_{ij}\)</dt><dd>The one-body reduced density matrix</dd>
<dt>\(\langle j |h| i \rangle\)</dt><dd>The one-electron Hamiltonian integrals</dd>
<dt>\(\Gamma_{ijkl}\)</dt><dd>The two-body reduced density matrix</dd>
<dt>\(\langle k l  | i j \rangle\)</dt><dd>The electron repulsion integrals</dd>
</dl>


<div class="org-src-container">
<pre class="src src-f90"><span style="color: #228b22;">integer</span>                       ::<span style="color: #a0522d;"> n</span>
<span style="color: #228b22;">double precision</span>              ::<span style="color: #a0522d;"> E, E_nn</span>
<span style="color: #228b22;">double precision</span>, <span style="color: #a020f0;">allocatable</span> ::<span style="color: #a0522d;"> D(:,:), h0(:,:)</span>
<span style="color: #228b22;">double precision</span>, <span style="color: #a020f0;">allocatable</span> ::<span style="color: #a0522d;"> G(:,:,:,:), W(:,:,:,:)</span>
</pre>
</div>
</div>

<div id="outline-container-org29b6380" class="outline-4">
<h4 id="org29b6380"><span class="section-number-4">1.1.1.</span> Declare Temporary variables</h4>
<div class="outline-text-4" id="text-1-1-1">
<div class="org-src-container">
<pre class="src src-f90"><span style="color: #228b22;">integer</span>                       ::<span style="color: #a0522d;"> i, j, k, l, m</span>
<span style="color: #228b22;">integer</span>(8), <span style="color: #a020f0;">parameter</span>         ::<span style="color: #a0522d;"> BUFSIZE = 100000_8</span>
<span style="color: #228b22;">integer</span>(8)                    ::<span style="color: #a0522d;"> offset, icount, size_max</span>
<span style="color: #228b22;">integer</span>                       ::<span style="color: #a0522d;"> buffer_index(4,BUFSIZE)</span>
<span style="color: #228b22;">double precision</span>              ::<span style="color: #a0522d;"> buffer_values(BUFSIZE)</span>

<span style="color: #228b22;">double precision</span>, <span style="color: #a020f0;">external</span>    ::<span style="color: #a0522d;"> ddot   </span>! <span style="color: #b22222;">BLAS dot product</span>
</pre>
</div>
</div>
</div>

<div id="outline-container-org4f6ee33" class="outline-4">
<h4 id="org4f6ee33"><span class="section-number-4">1.1.2.</span> Obtain the name of the TREXIO file from the command line, and open it for reading</h4>
<div class="outline-text-4" id="text-1-1-2">
<div class="org-src-container">
<pre class="src src-f90"><span style="color: #a020f0;">call</span> <span style="color: #0000ff;">getarg</span>(1, filename)

f = trexio_open (filename, <span style="color: #8b2252;">'r'</span>, TREXIO_HDF5, rc)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error opening TREXIO file: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>
</pre>
</div>
</div>
</div>

<div id="outline-container-orgce13fac" class="outline-4">
<h4 id="orgce13fac"><span class="section-number-4">1.1.3.</span> Read the nuclear repulsion energy</h4>
<div class="outline-text-4" id="text-1-1-3">
<div class="org-src-container">
<pre class="src src-f90">rc = trexio_read_nucleus_repulsion(f, E_nn)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading nuclear repulsion: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>
</pre>
</div>
</div>
</div>

<div id="outline-container-org156e32c" class="outline-4">
<h4 id="org156e32c"><span class="section-number-4">1.1.4.</span> Read the number of molecular orbitals</h4>
<div class="outline-text-4" id="text-1-1-4">
<div class="org-src-container">
<pre class="src src-f90">rc = trexio_read_mo_num(f, n)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading number of MOs: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>
</pre>
</div>
</div>
</div>

<div id="outline-container-orgad093f3" class="outline-4">
<h4 id="orgad093f3"><span class="section-number-4">1.1.5.</span> Allocate memory</h4>
<div class="outline-text-4" id="text-1-1-5">
<div class="org-src-container">
<pre class="src src-f90"><span style="color: #a020f0;">allocate</span>( D(n,n), h0(n,n) )
<span style="color: #a020f0;">allocate</span>( G(n,n,n,n), W(n,n,n,n) )
G(:,:,:,:) = 0.d0
W(:,:,:,:) = 0.d0
</pre>
</div>
</div>
</div>

<div id="outline-container-org3283c85" class="outline-4">
<h4 id="org3283c85"><span class="section-number-4">1.1.6.</span> Read one-electron quantities</h4>
<div class="outline-text-4" id="text-1-1-6">
<div class="org-src-container">
<pre class="src src-f90">rc = trexio_has_mo_1e_int_core_hamiltonian(f)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">stop</span> <span style="color: #8b2252;">'No core hamiltonian in file'</span>
<span style="color: #a020f0;">end if</span>

rc = trexio_read_mo_1e_int_core_hamiltonian(f, h0)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading core Hamiltonian: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>


rc = trexio_has_rdm_1e(f)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">stop</span> <span style="color: #8b2252;">'No 1e RDM in file'</span>
<span style="color: #a020f0;">end if</span>

rc = trexio_read_rdm_1e(f, D)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading one-body RDM: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>
</pre>
</div>
</div>
</div>

<div id="outline-container-orgcd6481c" class="outline-4">
<h4 id="orgcd6481c"><span class="section-number-4">1.1.7.</span> Read two-electron quantities</h4>
<div class="outline-text-4" id="text-1-1-7">
<p>
Reading is done with OpenMP. Each thread reads its own buffer, and
the buffers are then processed in parallel.
</p>

<p>
Reading the file requires a lock, so it is done in a critical
section. The <code>offset</code> variable is shared, and it is incremented in
the critical section. For each read, the function returns in
<code>icount</code> the number of read integrals, so this variable needs also
to be protected in the critical section when modified.
</p>
</div>

<div id="outline-container-org5d1e8d1" class="outline-5">
<h5 id="org5d1e8d1"><span class="section-number-5">1.1.7.1.</span> Electron repulsion integrals</h5>
<div class="outline-text-5" id="text-1-1-7-1">
<div class="org-src-container">
<pre class="src src-f90">rc = trexio_has_mo_2e_int_eri(f)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">stop</span> <span style="color: #8b2252;">'No electron repulsion integrals in file'</span>
<span style="color: #a020f0;">end if</span>

rc = trexio_read_mo_2e_int_eri_size (f, size_max)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading number of ERIs: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>

offset = 0_8
!<span style="color: #b22222;">$OMP PARALLEL DEFAULT(SHARED) PRIVATE(icount, i, j, k, l, &amp;</span>
!<span style="color: #b22222;">$OMP   buffer_index, buffer_values, m)</span>
icount = BUFSIZE
<span style="color: #a020f0;">do while</span> (icount == BUFSIZE)
  !<span style="color: #b22222;">$OMP CRITICAL</span>
  <span style="color: #a020f0;">if</span> (offset &lt; size_max) <span style="color: #a020f0;">then</span>
    rc = trexio_read_mo_2e_int_eri(f, offset, icount, buffer_index, buffer_values)
    offset = offset + icount
  <span style="color: #a020f0;">else</span>
    icount = 0
  <span style="color: #a020f0;">end if</span>
  !<span style="color: #b22222;">$OMP END CRITICAL</span>
  <span style="color: #a020f0;">do</span> m=1,icount
    i = buffer_index(1,m)
    j = buffer_index(2,m)
    k = buffer_index(3,m)
    l = buffer_index(4,m)
    W(i,j,k,l) = buffer_values(m)
    W(k,j,i,l) = buffer_values(m)
    W(i,l,k,j) = buffer_values(m)
    W(k,l,i,j) = buffer_values(m)
    W(j,i,l,k) = buffer_values(m)
    W(j,k,l,i) = buffer_values(m)
    W(l,i,j,k) = buffer_values(m)
    W(l,k,j,i) = buffer_values(m)
  <span style="color: #a020f0;">end do</span>
<span style="color: #a020f0;">end do</span>
!<span style="color: #b22222;">$OMP END PARALLEL</span>
</pre>
</div>
</div>
</div>

<div id="outline-container-orgf49354f" class="outline-5">
<h5 id="orgf49354f"><span class="section-number-5">1.1.7.2.</span> Reduced density matrix</h5>
<div class="outline-text-5" id="text-1-1-7-2">
<div class="org-src-container">
<pre class="src src-f90">rc = trexio_has_rdm_2e(f)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">stop</span> <span style="color: #8b2252;">'No two-body density matrix in file'</span>
<span style="color: #a020f0;">end if</span>

rc = trexio_read_rdm_2e_size (f, size_max)
<span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
   <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
   <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading number of 2-RDM elements: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
   <span style="color: #a020f0;">stop</span>
<span style="color: #a020f0;">end if</span>

offset = 0_8
!<span style="color: #b22222;">$OMP PARALLEL DEFAULT(SHARED) PRIVATE(icount, i, j, k, l, &amp;</span>
!<span style="color: #b22222;">$OMP   buffer_index, buffer_values, m)</span>
icount = bufsize
<span style="color: #a020f0;">do while</span> (offset &lt; size_max)
  !<span style="color: #b22222;">$OMP CRITICAL</span>
  <span style="color: #a020f0;">if</span> (offset &lt; size_max) <span style="color: #a020f0;">then</span>
    rc = trexio_read_rdm_2e(f, offset, icount, buffer_index, buffer_values)
    offset = offset + icount
  <span style="color: #a020f0;">else</span>
    icount = 0
  <span style="color: #a020f0;">end if</span>
  !<span style="color: #b22222;">$OMP END CRITICAL</span>
  <span style="color: #a020f0;">do</span> m=1,icount
    i = buffer_index(1,m)
    j = buffer_index(2,m)
    k = buffer_index(3,m)
    l = buffer_index(4,m)
    G(i,j,k,l) = buffer_values(m)
  <span style="color: #a020f0;">end do</span>
<span style="color: #a020f0;">end do</span>
!<span style="color: #b22222;">$OMP END PARALLEL</span>

</pre>
</div>
</div>
</div>
</div>

<div id="outline-container-orgcf80f54" class="outline-4">
<h4 id="orgcf80f54"><span class="section-number-4">1.1.8.</span> Compute the energy</h4>
<div class="outline-text-4" id="text-1-1-8">
<p>
When the orbitals are real, we can use
</p>
\begin{eqnarray*}
E &=& E_{\text{NN}} + \sum_{ij} \gamma_{ij}\, \langle j | h | i \rangle\,
+\, \frac{1}{2} \sum_{ijkl} \Gamma_{ijkl}\, \langle k l | i j
\rangle \\
  &=& E_{\text{NN}} + \sum_{ij} \gamma_{ij}\, \langle i | h | j \rangle\,
+\, \frac{1}{2} \sum_{ijkl} \Gamma_{ijkl}\, \langle i j | k l
\rangle \\
\end{eqnarray*}

<p>
As \((n,m)\) 2D arrays are stored in memory as \((n \times m)\) 1D
arrays, we could pass the matrices to the <code>ddot</code> BLAS function to
perform the summations in a single call for the 1-electron quantities.
Instead, we prefer to interleave the 1-electron (negative) and
2-electron (positive) summations to have a better cancellation of
numerical errors.
</p>

<p>
Here \(n^4\) can be larger than the largest possible 32-bit integer,
so it is not safe to pass \(n^4\) to the <code>ddot</code> BLAS
function. Hence, we perform \(n^2\) loops, using vectors of size \(n^2\).
</p>

<div class="org-src-container">
<pre class="src src-f90">
E = 0.d0
<span style="color: #a020f0;">do</span> l=1,n
  E = E + ddot( n, D(1,l), 1, h0(1,l), 1 ) 
  <span style="color: #a020f0;">do</span> k=1,n
     E = E + 0.5d0 * ddot( n*n, G(1,1,k,l), 1, W(1,1,k,l),  1 )
  <span style="color: #a020f0;">end do</span>
<span style="color: #a020f0;">end do</span>
E = E + E_nn

<span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Energy: '</span>, E
</pre>
</div>
</div>
</div>

<div id="outline-container-org27007da" class="outline-4">
<h4 id="org27007da"><span class="section-number-4">1.1.9.</span> Terminate</h4>
<div class="outline-text-4" id="text-1-1-9">
<div class="org-src-container">
<pre class="src src-f90">  <span style="color: #a020f0;">deallocate</span>( D, h0, G, W )

<span style="color: #a020f0;">end program</span>
</pre>
</div>
</div>
</div>
</div>
</div>


<div id="outline-container-org861bef9" class="outline-2">
<h2 id="org861bef9"><span class="section-number-2">2.</span> Reading determinants</h2>
<div class="outline-text-2" id="text-2">
</div>
<div id="outline-container-org8ca1578" class="outline-3">
<h3 id="org8ca1578"><span class="section-number-3">2.1.</span> Fortran</h3>
<div class="outline-text-3" id="text-2-1">
<div class="org-src-container">
<pre class="src src-f90"><span style="color: #a020f0;">program</span> <span style="color: #0000ff;">test</span>

  <span style="color: #a020f0;">use</span> <span style="color: #0000ff;">trexio</span>
  <span style="color: #a020f0;">implicit</span> <span style="color: #228b22;">none</span>

  <span style="color: #228b22;">character</span>*(128)           ::<span style="color: #a0522d;"> filename               </span>! <span style="color: #b22222;">Name of the input file</span>
  <span style="color: #228b22;">integer</span>(trexio_exit_code) ::<span style="color: #a0522d;"> rc                     </span>! <span style="color: #b22222;">Return code for error checking</span>
  <span style="color: #228b22;">integer</span>(trexio_t)         ::<span style="color: #a0522d;"> trex_determinant_file  </span>! <span style="color: #b22222;">TREXIO file handle</span>
  <span style="color: #228b22;">character</span>*(128)           ::<span style="color: #a0522d;"> err_msg                </span>! <span style="color: #b22222;">Error message</span>


  <span style="color: #228b22;">integer</span>*8, <span style="color: #a020f0;">allocatable</span> ::<span style="color: #a0522d;"> buffer(:,:,:)</span>
  <span style="color: #228b22;">integer</span>(8) ::<span style="color: #a0522d;"> offset, icount, BUFSIZE</span>
  <span style="color: #228b22;">integer</span> ::<span style="color: #a0522d;"> ndet, int64_num, m</span>

  <span style="color: #228b22;">integer</span> ::<span style="color: #a0522d;"> occ_num_up, occ_num_dn</span>
  <span style="color: #228b22;">integer</span>, <span style="color: #a020f0;">allocatable</span> ::<span style="color: #a0522d;"> orb_list_up(:), orb_list_dn(:)</span>

  <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">getarg</span>(1, filename)

  trex_determinant_file = trexio_open(filename, <span style="color: #8b2252;">'r'</span>, TREXIO_AUTO, rc)
  <span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
     <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
     <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error opening TREXIO file: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
     <span style="color: #a020f0;">stop</span>
  <span style="color: #a020f0;">end if</span>

  rc = trexio_read_determinant_num(trex_determinant_file, ndet)
  <span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
     <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
     <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading determinant_num: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
     <span style="color: #a020f0;">stop</span>
  <span style="color: #a020f0;">end if</span>
  <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'ndet'</span>, ndet

  rc = trexio_get_int64_num(trex_determinant_file, int64_num)
  <span style="color: #a020f0;">if</span> (rc /= TREXIO_SUCCESS) <span style="color: #a020f0;">then</span>
     <span style="color: #a020f0;">call</span> <span style="color: #0000ff;">trexio_string_of_error</span>(rc, err_msg)
     <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'Error reading int64_num: '</span>//<span style="color: #a020f0;">trim</span>(err_msg)
     <span style="color: #a020f0;">stop</span>
  <span style="color: #a020f0;">end if</span>
  <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'int64_num'</span>, int64_num

  BUFSIZE = 1000_8
  <span style="color: #a020f0;">allocate</span>(buffer(int64_num, 2, BUFSIZE))
  <span style="color: #a020f0;">allocate</span>(orb_list_up(int64_num*64), orb_list_dn(int64_num*64))

  offset = 0_8
  icount = BUFSIZE
  <span style="color: #a020f0;">do while</span> (icount == BUFSIZE)
    <span style="color: #a020f0;">if</span> (offset &lt; ndet) <span style="color: #a020f0;">then</span>
      rc = trexio_read_determinant_list(trex_determinant_file, offset, icount, buffer)
      offset = offset + icount
    <span style="color: #a020f0;">else</span>
      icount = 0
    <span style="color: #a020f0;">end if</span>
    <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">'---'</span>
    <span style="color: #a020f0;">do</span> m=1,icount
      rc = trexio_to_orbital_list_up_dn(int64_num, buffer(1,1,m), <span style="color: #a020f0;">&amp;</span>
           orb_list_up, orb_list_dn, occ_num_up, occ_num_dn)
      <span style="color: #a020f0;">print</span> <span style="color: #8b2252;">'(100(I3,X))'</span>, (orb_list_up(1:occ_num_up)), (orb_list_dn(1:occ_num_dn))
      <span style="color: #a020f0;">print</span> *, <span style="color: #8b2252;">''</span>
    <span style="color: #a020f0;">end do</span>
  <span style="color: #a020f0;">end do</span>

  <span style="color: #a020f0;">deallocate</span>(buffer, orb_list_dn, orb_list_up)

end
</pre>
</div>
</div>
</div>
</div>
</div>
<div id="postamble" class="status">
<p class="author">Author: TREX-CoE</p>
<p class="date">Created: 2022-09-29 Thu 11:40</p>
<p class="validation"><a href="https://validator.w3.org/check?uri=referer">Validate</a></p>
</div>
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</html>