<div dir="ltr"><div dir="ltr"><p>Hello,</p><p>I've been stuck on an issue and encountered the following error:</p><pre class="gmail-!overflow-visible"><div class="gmail-contain-inline-size gmail-rounded-md gmail-border-[0.5px] gmail-border-token-border-medium gmail-relative gmail-bg-token-sidebar-surface-primary gmail-dark:bg-gray-950"><div class="gmail-overflow-y-auto gmail-p-4" dir="ltr"><code class="gmail-!whitespace-pre gmail-hljs gmail-language-yaml">[<span class="gmail-hljs-string">solve.c:4676</span>] <span class="gmail-hljs-attr">ERROR:</span> <span class="gmail-hljs-string">pricing</span> <span class="gmail-hljs-string">was</span> <span class="gmail-hljs-string">aborted,</span> <span class="gmail-hljs-string">but</span> <span class="gmail-hljs-literal">no</span> <span class="gmail-hljs-string">branching</span> <span class="gmail-hljs-string">could</span> <span class="gmail-hljs-string">be</span> <span class="gmail-hljs-string">created!</span>
</code></div></div></pre><p>To investigate, I exported the pricing model using the following code:</p><pre class="gmail-!overflow-visible"><div class="gmail-contain-inline-size gmail-rounded-md gmail-border-[0.5px] gmail-border-token-border-medium gmail-relative gmail-bg-token-sidebar-surface-primary gmail-dark:bg-gray-950"><div class="gmail-overflow-y-auto gmail-p-4" dir="ltr"><code class="gmail-!whitespace-pre gmail-hljs gmail-language-c">SCIP_CALL( SCIPsolve(subscip) );
SCIPwriteOrigProblem(subscip, filename, <span class="gmail-hljs-literal">NULL</span>, TRUE);
</code></div></div></pre><p>I adapted the BinPacking example for my problem. However, in my pricing problem, I replaced the knapsack constraint with a linear constraint. Specifically, I commented out the knapsack constraint and added mine like what follows:</p><pre class="gmail-!overflow-visible"><div class="gmail-contain-inline-size gmail-rounded-md gmail-border-[0.5px] gmail-border-token-border-medium gmail-relative gmail-bg-token-sidebar-surface-primary gmail-dark:bg-gray-950"><div class="gmail-overflow-y-auto gmail-p-4" dir="ltr"><code class="gmail-!whitespace-pre gmail-hljs gmail-language-c"><span class="gmail-hljs-comment">/* Create capacity constraint */</span>
SCIPcreateConsBasicLinear(subscip, &cons, <span class="gmail-hljs-string">"edgesum"</span>, nvars, vars, vals, capacity, capacity);
<span class="gmail-hljs-comment">// SCIPcreateConsBasicKnapsack(subscip, &cons, "edgesum", nvars, vars, vals, capacity);</span>
SCIP_CALL( SCIPaddCons(subscip, cons) );
SCIP_CALL( SCIPreleaseCons(subscip, &cons) );
</code></div></div></pre><p>When I checked the output, the linear constraint did not appear in the exported problem:</p><pre class="gmail-!overflow-visible"><div class="gmail-contain-inline-size gmail-rounded-md gmail-border-[0.5px] gmail-border-token-border-medium gmail-relative gmail-bg-token-sidebar-surface-primary gmail-dark:bg-gray-950"><div class="gmail-overflow-y-auto gmail-p-4" dir="ltr"><code class="gmail-!whitespace-pre gmail-hljs gmail-language-php-template">\ SCIP STATISTICS
\ Problem name : pricing
\ Variables : 15 (15 binary, 0 integer, 0 implicit integer, 0 continuous)
\ Constraints : 7
Maximize
Obj: +1 x4
Subject to
c0: = +3
\ [linking] <span class="gmail-hljs-tag"><<span class="gmail-hljs-name">c1</span>></span>: <span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x10</span>></span> = +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x0</span>></span> +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x1</span>></span> +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x2</span>></span> +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x3</span>></span>;
...
</code></div></div></pre><p>However, when I used the knapsack constraint instead, the problem was correctly formulated:</p><pre class="gmail-!overflow-visible"><div class="gmail-contain-inline-size gmail-rounded-md gmail-border-[0.5px] gmail-border-token-border-medium gmail-relative gmail-bg-token-sidebar-surface-primary gmail-dark:bg-gray-950"><div class="gmail-overflow-y-auto gmail-p-4" dir="ltr"><code class="gmail-!whitespace-pre gmail-hljs gmail-language-php-template">\ SCIP STATISTICS
\ Problem name : pricing
\ Variables : 15 (15 binary, 0 integer, 0 implicit integer, 0 continuous)
\ Constraints : 7
Maximize
Obj: +1 x4
Subject to
c0: +1 x0 +1 x1 +1 x2 +1 x3 +1 x4 +1 x5 +1 x6 +1 x7 +1 x8 +1 x9 <= +3
\ [linking] <span class="gmail-hljs-tag"><<span class="gmail-hljs-name">c1</span>></span>: <span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x10</span>></span> = +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x0</span>></span> +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x1</span>></span> +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x2</span>></span> +0.5<span class="gmail-hljs-tag"><<span class="gmail-hljs-name">x3</span>></span>;
...
</code></div></div></pre><p>Is this a bug in SCIP?</p><p>PS:<br>I also tried using <code>SCIPcreateConsLinear</code>, but the result was the same. Additionally, I attempted to circumvent the issue by adding another knapsack constraint with a negated version of the original equation so that force what I wanted:</p><pre class="gmail-!overflow-visible"><div class="gmail-contain-inline-size gmail-rounded-md gmail-border-[0.5px] gmail-border-token-border-medium gmail-relative gmail-bg-token-sidebar-surface-primary gmail-dark:bg-gray-950"><div class="gmail-overflow-y-auto gmail-p-4" dir="ltr"><code class="gmail-!whitespace-pre gmail-hljs gmail-language-diff"><span class="gmail-hljs-deletion">-1 x0 -1 x1 -1 x2 -1 x3 -1 x4 -1 x5 -1 x6 -1 x7 -1 x8 -1 x9 <= -3</span>
</code></div></div></pre><p>However, this constraint was also not added to the pricing problem.</p><p>Best regards,<br>Mahdi Mohammadi</p></div></div>