<p dir="auto">This was exposed by <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="41605209" data-permission-text="Title is private" data-url="https://github.com/JuliaLang/julia/issues/8200" data-hovercard-type="issue" data-hovercard-url="/JuliaLang/julia/issues/8200/hovercard" href="https://github.com/JuliaLang/julia/issues/8200">#8200</a> and "fixed" by <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="41783430" data-permission-text="Title is private" data-url="https://github.com/JuliaLang/julia/issues/8218" data-hovercard-type="pull_request" data-hovercard-url="/JuliaLang/julia/pull/8218/hovercard" href="https://github.com/JuliaLang/julia/pull/8218">#8218</a>, but the underlying problem that caused the segfault to randomly show up and disappear when rebuilding julia is probably still exists.</p>
<p dir="auto">To summarize the thread in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="41605209" data-permission-text="Title is private" data-url="https://github.com/JuliaLang/julia/issues/8200" data-hovercard-type="issue" data-hovercard-url="/JuliaLang/julia/issues/8200/hovercard" href="https://github.com/JuliaLang/julia/issues/8200">#8200</a>, there's a bug that causes a segfault. However, it only affects some builds. Rebuilding can make the bug appear or disappear, and running with <code class="notranslate">make -j n</code>, for different <code class="notranslate">n</code>, seems to affect the probability of a bad build.</p>
<p dir="auto">cc <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/StefanKarpinski/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://github.com/StefanKarpinski">@StefanKarpinski</a> , since he seemed interested in this.</p>
<p dir="auto">Based on the discussion here, we need to investigate if <code class="notranslate">sparse()</code> can be sped up.</p>
<p dir="auto"><a href="https://groups.google.com/forum/#!topic/julia-users/X8Jca4SZMxo" rel="nofollow">https://groups.google.com/forum/#!topic/julia-users/X8Jca4SZMxo</a></p>
<p dir="auto">Potential opportunities include experimenting with different ways of sorting inputs, avoiding the use of the generic <code class="notranslate">combine</code> function, <code class="notranslate">@inbounds</code>, etc.</p>
<p dir="auto">The following example takes 1.7 seconds for me:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="s = sprand(70000,70000,0.001)"><pre class="notranslate"><code class="notranslate">s = sprand(70000,70000,0.001)
</code></pre></div>