<p dir="auto">This is about the "documentation inaccuracy" and the discussion on "scale_C".<br>
I really want to fix this before the release but I don't have much time atm.</p>
<p dir="auto">As far as I understood, at the moment we can agree that having "C" as parameter with "scale_C=True"<br>
is not perfect, as this doesn't agree with how "C" is used in the literature / other software.<br>
I am not sure if there was a solution that we could agree on.<br>
I would like to have votes pro/con having a "duplicate" parameter C (which has scale_C=False semantics) and alpha, which behaves as in the other linear models. Another option would be to have just the "alpha" parameter.<br>
Any other suggestions are welcome.</p>
<p dir="auto">I created this script: <a href="https://gist.github.com/2354823">https://gist.github.com/2354823</a> to understand the effect of "scale_C".<br>
Not sure if that helps.<br>
Results look like this:<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/ecb5d47a0be5d6b6ab4c33dbe14435b49b1116ebf43b21550328d836f6f1602b/687474703a2f2f692e696d6775722e636f6d2f366d4b31712e706e67"><img src="https://camo.githubusercontent.com/ecb5d47a0be5d6b6ab4c33dbe14435b49b1116ebf43b21550328d836f6f1602b/687474703a2f2f692e696d6775722e636f6d2f366d4b31712e706e67" alt="true" data-canonical-src="http://i.imgur.com/6mK1q.png" style="max-width: 100%;"></a><br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/7a4d6fa96dd71543182085a34ec0ac41d97752ee212e6371618aaa2304b429ca/687474703a2f2f692e696d6775722e636f6d2f474156694e2e706e67"><img src="https://camo.githubusercontent.com/7a4d6fa96dd71543182085a34ec0ac41d97752ee212e6371618aaa2304b429ca/687474703a2f2f692e696d6775722e636f6d2f474156694e2e706e67" alt="false" data-canonical-src="http://i.imgur.com/GAViN.png" style="max-width: 100%;"></a><br>
These are grid searches for C=2**k with "shuffle &amp; split" and different fractions of training data.<br>
In principle the results should just be shifted by a factor of "n_samples". Guess that is not a power of two so that makes it a bit different. Not sure I like one more than the other.</p>
<h1 dir="auto">problem</h1>
<p dir="auto">I am trying to get the <code class="notranslate">nmf_missing</code> branch to compile without success, <a href="https://github.com/scikit-learn/scikit-learn/pull/8474#issuecomment-347520280" data-hovercard-type="pull_request" data-hovercard-url="/scikit-learn/scikit-learn/pull/8474/hovercard">as per this suggestion</a>.</p>
<h2 dir="auto">The compiler error:</h2>
<p dir="auto">On branch <code class="notranslate">nmf_missing</code> after issuing <code class="notranslate">make</code> at the command line it build largely fine until the following error (The first one I know of, although several warnings):</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="error: Command &quot;x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/local/lib/python2.7/dist-packages/numpy/core/include -I/usr/local/lib/python2.7/dist-packages/numpy/core/include -I/usr/include/python2.7 -c sklearn/neighbors/quad_tree.c -o build/temp.linux-x86_64-2.7/sklearn/neighbors/quad_tree.o -MMD -MF build/temp.linux-x86_64-2.7/sklearn/neighbors/quad_tree.o.d&quot; failed with exit status 1
Makefile:24: recipe for target 'inplace' failed"><pre class="notranslate"><code class="notranslate">error: Command "x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fno-strict-aliasing -Wdate-time -D_FORTIFY_SOURCE=2 -g -fstack-protector-strong -Wformat -Werror=format-security -fPIC -I/usr/local/lib/python2.7/dist-packages/numpy/core/include -I/usr/local/lib/python2.7/dist-packages/numpy/core/include -I/usr/include/python2.7 -c sklearn/neighbors/quad_tree.c -o build/temp.linux-x86_64-2.7/sklearn/neighbors/quad_tree.o -MMD -MF build/temp.linux-x86_64-2.7/sklearn/neighbors/quad_tree.o.d" failed with exit status 1
Makefile:24: recipe for target 'inplace' failed
</code></pre></div>
<h3 dir="auto">How I think this can be solved(?)</h3>
<p dir="auto">It seems to come from trying to compile the following line in quad_tree.c (3582) <code class="notranslate">      printf(__pyx_k_QuadTree_found_a_duplicate);</code>. I have tried commenting out this line but whenever I type <code class="notranslate">make</code> it reverts the change. Hence I have tried tracking down what is producing either this file, or whatever is producing the compiler flags <code class="notranslate">-Wformat -Werror=format-security</code> which is causing the compiler to throw the error. However, trying to track the origin of these has proved too much and I am lost.</p>