<div dir="ltr"><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI Adjusted","Segoe UI","Liberation Sans",sans-serif;font-size:15px">Considering, for instance, the following COO sparse matrix format, with repeated indices:</span><div><span style="background-color:transparent;font-family:inherit;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit"><br></span></div><div><font face="monospace"><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">std::vector<</span><span class="gmail-hljs-type" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">size_t</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">> rows{</span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">};</span></font></div><div><font face="monospace"><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">std::vector<</span><span class="gmail-hljs-type" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">size_t</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">> cols{</span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">};</span></font></div><div><font face="monospace"><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">std::vector<</span><span class="gmail-hljs-type" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">double</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">> values{</span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">-1</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">, </span><span class="gmail-hljs-number" style="background-color:transparent;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">5</span><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">};</span></font><div><br></div><div>that represents a 5x5 diagonal matrix A.</div><div><br></div><div>So far, the code that I have is:</div><div><br></div><div><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit"><span class="gmail-hljs-comment" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">// fill_in_matrix.cc</span>

<span class="gmail-hljs-type" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">static</span> <span class="gmail-hljs-type" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">char</span> help[] = <span class="gmail-hljs-string" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">"Fill in a parallel COO format sparse matrix."</span>;

<span class="gmail-hljs-meta" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">#<span class="gmail-hljs-keyword" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">include</span> <span class="gmail-hljs-string" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit"><petsc.h></span></span>
<span class="gmail-hljs-meta" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">#<span class="gmail-hljs-keyword" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">include</span> <span class="gmail-hljs-string" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit"><vector></span></span>

<span class="gmail-hljs-function" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit"><span class="gmail-hljs-type" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">int</span> <span class="gmail-hljs-title" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">main</span><span class="gmail-hljs-params" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">(<span class="gmail-hljs-type" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">int</span> argc, <span class="gmail-hljs-type" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit">char</span> **args)</span>
</span>{
    Mat A;
    PetscInt m = <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">5</span>, i, Istart, Iend;

    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscInitialize</span>(&argc, &args, <span class="gmail-hljs-literal" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">NULL</span>, help));

    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatCreate</span>(PETSC_COMM_WORLD, &A));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatSetSizes</span>(A, PETSC_DECIDE, PETSC_DECIDE, m, m));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatSetFromOptions</span>(A));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatSetUp</span>(A));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatGetOwnershipRange</span>(A, &Istart, &Iend));

    std::vector<PetscInt> II{<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span>};
    std::vector<PetscInt> JJ{<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span>};
    std::vector<PetscScalar> XX{<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">-1</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">5</span>};

    <span class="gmail-hljs-keyword" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">for</span> (i = Istart; i < Iend; i++)
        <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatSetValues</span>(A, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span>, &II.<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">at</span>(i), <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span>, &JJ.<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">at</span>(i), &XX.<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">at</span>(i), ADD_VALUES));

    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatAssemblyBegin</span>(A, MAT_FINAL_ASSEMBLY));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatAssemblyEnd</span>(A, MAT_FINAL_ASSEMBLY));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatView</span>(A, PETSC_VIEWER_STDERR_WORLD));

    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">MatDestroy</span>(&A));
    <span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscCall</span>(<span class="gmail-hljs-built_in" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">PetscFinalize</span>());
    <span class="gmail-hljs-keyword" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">return</span> <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>;
}</code></pre></div><div><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI Adjusted","Segoe UI","Liberation Sans",sans-serif;font-size:15px">When running it with</span><br></div><div><span style="color:rgb(35,38,41);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI Adjusted","Segoe UI","Liberation Sans",sans-serif;font-size:15px"><br></span></div><div><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit">petscmpiexec -n <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span> ./fill_in_matrix</code></pre><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit"><br></code></pre><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><font face="arial, sans-serif"><span style="background-color:transparent;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">I get</span><br></font></pre><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit"><br></code></pre></div><div> <span style="background-color:transparent;font-family:inherit;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit">Mat Object: </span><span class="gmail-hljs-number" style="background-color:transparent;font-family:inherit;font-style:inherit;font-variant:inherit;font-weight:inherit;white-space:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span><span style="background-color:transparent;font-family:inherit;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;white-space:inherit"> MPI processes</span></div><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit">  type: mpiaij
row <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>: (<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">0</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1.</span>) 
row <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span>: (<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">1</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2.</span>) 
row <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span>: (<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">2</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3.</span>) 
row <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span>: (<span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">3</span>, <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4.</span>) 
row <span class="gmail-hljs-number" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;font-size:13px;vertical-align:baseline;box-sizing:inherit">4</span>:</code></pre><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit"><br></code></pre><pre class="gmail-lang-cpp gmail-s-code-block" style="margin-top:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto"><code class="gmail-hljs gmail-language-cpp" style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;font-kerning:inherit;font-feature-settings:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit"><p style="margin:0px 0px 1.1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI Adjusted","Segoe UI","Liberation Sans",sans-serif;font-kerning:inherit;font-feature-settings:inherit;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(35,38,41);white-space:normal">Which is missing the entry of the last row.</p><p style="margin:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-variant-alternates:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI Adjusted","Segoe UI","Liberation Sans",sans-serif;font-kerning:inherit;font-feature-settings:inherit;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(35,38,41);white-space:normal">What am I missing? Even better, which would be the best way to fill in this matrix?</p></code></pre></div></div>