<p dir="auto">While using scipy.optimize.linprog(method="highs"), I encountered a status message stating "The solver did not provide a solution nor did it report a failure" and asking for a bug report, which I am hereby writing :-)</p>
<p dir="auto">As I have little experience in numerics, I make no claims about the qualities (feasibility, boundedness, etc) of the problem I was trying to solve. (I was trying to deactivate bounds I did not require by setting b_ub elements to a large value (100000.0). I have no idea if that is part of the problem.)</p>
<h4 dir="auto">Reproducing code example:</h4>

<p dir="auto">Please see the attached file for problem parameters: <a href="https://github.com/scipy/scipy/files/6221882/bug_reproducer.py.gz">bug_reproducer.py.gz</a> (Some 3MB uncompressed. As I have no idea what is causing the problem, I can not build a minimal reproducer, sorry).<br>
Gist of the code:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="import numpy, scipy.optimize

c=...
A_ub=...
b_ub=...
res=scipy.optimize.linprog(c=c, A_ub=A_ub, b_ub=b_ub, method='highs')
print('status=', res.status)
print('message=', res.message)"><pre class="notranslate"><code class="notranslate">import numpy, scipy.optimize

c=...
A_ub=...
b_ub=...
res=scipy.optimize.linprog(c=c, A_ub=A_ub, b_ub=b_ub, method='highs')
print('status=', res.status)
print('message=', res.message)
</code></pre></div>
<h4 dir="auto">Error message:</h4>

<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="/home/philipp/.local/lib/python3.7/site-packages/scipy/optimize/_linprog_highs.py:317: OptimizeWarning: model_status is not optimal, using scaled_model_status instead.
  lb, ub, options)
status= 4
message= The solver did not provide a solution nor did it report a failure. Please submit a bug report."><pre class="notranslate"><code class="notranslate">/home/philipp/.local/lib/python3.7/site-packages/scipy/optimize/_linprog_highs.py:317: OptimizeWarning: model_status is not optimal, using scaled_model_status instead.
  lb, ub, options)
status= 4
message= The solver did not provide a solution nor did it report a failure. Please submit a bug report.
</code></pre></div>
<h4 dir="auto">Scipy/Numpy/Python version information:</h4>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="&gt;import sys, scipy, numpy; print(scipy.__version__, numpy.__version__, sys.version_info)
1.6.1 1.20.1 sys.version_info(major=3, minor=7, micro=3, releaselevel='final', serial=0)"><pre class="notranslate"><code class="notranslate">&gt;import sys, scipy, numpy; print(scipy.__version__, numpy.__version__, sys.version_info)
1.6.1 1.20.1 sys.version_info(major=3, minor=7, micro=3, releaselevel='final', serial=0)
</code></pre></div>
<p dir="auto">Thanks for your time,<br>
Philipp</p>
<p dir="auto">My issue is about <code class="notranslate">scipy.optimize.linprog(c, A_ub=A_ub, b_ub=b_ub, A_eq=A_eq, b_eq=b_eq, method='highs')</code> telling me to submit a bug report.</p>
<h4 dir="auto">Reproducing code example:</h4>
<p dir="auto">See minimal reproducer in a comment<br>
<a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="815830537" data-permission-text="Title is private" data-url="https://github.com/scipy/scipy/issues/13610" data-hovercard-type="issue" data-hovercard-url="/scipy/scipy/issues/13610/hovercard?comment_id=785620302&amp;comment_type=issue_comment" href="https://github.com/scipy/scipy/issues/13610#issuecomment-785620302">#13610 (comment)</a></p>
<h4 dir="auto">Error message:</h4>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="/home/chn/env/lib/python3.8/site-packages/scipy/optimize/_linprog_highs.py:316: OptimizeWarning: model_status is not optimal, using scaled_model_status instead.
  res = _highs_wrapper(c, A.indptr, A.indices, A.data, lhs, rhs,
The solver did not provide a solution nor did it report a failure. Please submit a bug report."><pre class="notranslate"><code class="notranslate">/home/chn/env/lib/python3.8/site-packages/scipy/optimize/_linprog_highs.py:316: OptimizeWarning: model_status is not optimal, using scaled_model_status instead.
  res = _highs_wrapper(c, A.indptr, A.indices, A.data, lhs, rhs,
The solver did not provide a solution nor did it report a failure. Please submit a bug report.
</code></pre></div>
<h4 dir="auto">Scipy/Numpy/Python version information:</h4>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="1.6.1 1.18.3 sys.version_info(major=3, minor=8, micro=5, releaselevel='final', serial=0)"><pre class="notranslate"><code class="notranslate">1.6.1 1.18.3 sys.version_info(major=3, minor=8, micro=5, releaselevel='final', serial=0)
</code></pre></div>