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  <h1>User manual</h1>

<h2 id="compile-the-library">Compile the library</h2>
<h3 id="normal-compile">Normal compile</h3>
<ul>
<li>type <code>make</code> to detect the CPU automatically.
  or</li>
<li>type <code>make TARGET=xxx</code> to set target CPU, e.g. <code>make TARGET=NEHALEM</code>. The full target list is in file TargetList.txt.</li>
</ul>
<h3 id="cross-compile">Cross compile</h3>
<p>Please set <code>CC</code> and <code>FC</code> with the cross toolchains. Then, set <code>HOSTCC</code> with your host C compiler. At last, set <code>TARGET</code> explicitly.</p>
<p>Examples:</p>
<ul>
<li>On x86 box, compile the library for ARM Cortex-A9 linux.</li>
</ul>
<p>Install only gnueabihf versions. Please check https://github.com/xianyi/OpenBLAS/issues/936#issuecomment-237596847</p>
<pre><code>make CC=arm-linux-gnueabihf-gcc FC=arm-linux-gnueabihf-gfortran HOSTCC=gcc TARGET=CORTEXA9
</code></pre>
<ul>
<li>On X86 box, compile this library for loongson3a CPU.</li>
</ul>
<div class="highlight"><pre><span></span><code>make BINARY=64 CC=mips64el-unknown-linux-gnu-gcc FC=mips64el-unknown-linux-gnu-gfortran HOSTCC=gcc TARGET=LOONGSON3A
</code></pre></div>
<ul>
<li>On X86 box, compile this library for loongson3a CPU with loongcc (based on Open64) compiler.</li>
</ul>
<div class="highlight"><pre><span></span><code>make CC=loongcc FC=loongf95 HOSTCC=gcc TARGET=LOONGSON3A CROSS=1 CROSS_SUFFIX=mips64el-st-linux-gnu-   NO_LAPACKE=1 NO_SHARED=1 BINARY=32
</code></pre></div>
<h3 id="debug-version">Debug version</h3>
<pre><code>make DEBUG=1
</code></pre>
<h3 id="install-to-the-directory-optional">Install to the directory (optional)</h3>
<p>Example:</p>
<pre><code>make install PREFIX=your_installation_directory
</code></pre>
<p>The default directory is /opt/OpenBLAS. Note that any flags passed to <code>make</code> during build should also be passed to <code>make install</code> to circumvent any install errors, i.e. some headers not being copied over correctly.</p>
<p>For more information, please read <a href="../install/">Installation Guide</a>.</p>
<h2 id="link-the-library">Link the library</h2>
<ul>
<li>Link shared library</li>
</ul>
<div class="highlight"><pre><span></span><code>gcc -o test test.c -I/your_path/OpenBLAS/include/ -L/your_path/OpenBLAS/lib -Wl,-rpath,/your_path/OpenBLAS/lib -lopenblas
</code></pre></div>
<p>The <code>-Wl,-rpath,/your_path/OpenBLAS/lib</code> option to linker can be omitted if you ran <code>ldconfig</code> to update linker cache, put <code>/your_path/OpenBLAS/lib</code> in <code>/etc/ld.so.conf</code> or a file in <code>/etc/ld.so.conf.d</code>, or installed OpenBLAS in a location that is part of the <code>ld.so</code> default search path (usually /lib,/usr/lib and /usr/local/lib). Alternatively, you can set the environment variable LD_LIBRARY_PATH to point to the folder that contains libopenblas.so. Otherwise, linking at runtime will fail with a message like <code>cannot open shared object file: no such file or directory</code></p>
<p>If the library is multithreaded, please add <code>-lpthread</code>. If the library contains LAPACK functions, please add <code>-lgfortran</code> or other Fortran libs, although if you only make calls to LAPACKE routines, i.e. your code has <code>#include "lapacke.h"</code> and makes calls to methods like <code>LAPACKE_dgeqrf</code>, <code>-lgfortran</code> is not needed.</p>
<ul>
<li>Link static library</li>
</ul>
<div class="highlight"><pre><span></span><code>gcc -o test test.c /your/path/libopenblas.a
</code></pre></div>
<p>You can download <code>test.c</code> from https://gist.github.com/xianyi/5780018 </p>
<h2 id="code-examples">Code examples</h2>
<h3 id="call-cblas-interface">Call CBLAS interface</h3>
<p>This example shows calling cblas_dgemm in C. https://gist.github.com/xianyi/6930656
<div class="highlight"><pre><span></span><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;cblas.h&gt;</span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;stdio.h&gt;</span>

<span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">A</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">2.0</span><span class="p">,</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">-3.0</span><span class="p">,</span><span class="mf">4.0</span><span class="p">,</span><span class="mf">-1.0</span><span class="p">};</span><span class="w">         </span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">B</span><span class="p">[</span><span class="mi">6</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">2.0</span><span class="p">,</span><span class="mf">1.0</span><span class="p">,</span><span class="mf">-3.0</span><span class="p">,</span><span class="mf">4.0</span><span class="p">,</span><span class="mf">-1.0</span><span class="p">};</span><span class="w">  </span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">C</span><span class="p">[</span><span class="mi">9</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">,</span><span class="mf">.5</span><span class="p">};</span><span class="w"> </span>
<span class="w">  </span><span class="n">cblas_dgemm</span><span class="p">(</span><span class="n">CblasColMajor</span><span class="p">,</span><span class="w"> </span><span class="n">CblasNoTrans</span><span class="p">,</span><span class="w"> </span><span class="n">CblasTrans</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="n">C</span><span class="p">,</span><span class="mi">3</span><span class="p">);</span>

<span class="w">  </span><span class="k">for</span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="mi">9</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span>
<span class="w">    </span><span class="n">printf</span><span class="p">(</span><span class="s">&quot;%lf &quot;</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">[</span><span class="n">i</span><span class="p">]);</span>
<span class="w">  </span><span class="n">printf</span><span class="p">(</span><span class="s">&quot;</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div></p>
<div class="highlight"><pre><span></span><code>gcc -o test_cblas_open test_cblas_dgemm.c -I /your_path/OpenBLAS/include/ -L/your_path/OpenBLAS/lib -lopenblas -lpthread -lgfortran
</code></pre></div>
<h3 id="call-blas-fortran-interface">Call BLAS Fortran interface</h3>
<p>This example shows calling dgemm Fortran interface in C. https://gist.github.com/xianyi/5780018</p>
<div class="highlight"><pre><span></span><code><span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;stdio.h&quot;</span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;stdlib.h&quot;</span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;sys/time.h&quot;</span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;time.h&quot;</span>

<span class="k">extern</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">dgemm_</span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="p">,</span><span class="kt">int</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="p">);</span>

<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">argc</span><span class="p">,</span><span class="w"> </span><span class="kt">char</span><span class="o">*</span><span class="w"> </span><span class="n">argv</span><span class="p">[])</span>
<span class="p">{</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span>
<span class="w">  </span><span class="n">printf</span><span class="p">(</span><span class="s">&quot;test!</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">);</span>
<span class="w">  </span><span class="k">if</span><span class="p">(</span><span class="n">argc</span><span class="o">&lt;</span><span class="mi">4</span><span class="p">){</span>
<span class="w">    </span><span class="n">printf</span><span class="p">(</span><span class="s">&quot;Input Error</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">);</span>
<span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span>
<span class="w">  </span><span class="p">}</span>

<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atoi</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">]);</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atoi</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">2</span><span class="p">]);</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">atoi</span><span class="p">(</span><span class="n">argv</span><span class="p">[</span><span class="mi">3</span><span class="p">]);</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">sizeofa</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">k</span><span class="p">;</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">sizeofb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">k</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">n</span><span class="p">;</span>
<span class="w">  </span><span class="kt">int</span><span class="w"> </span><span class="n">sizeofc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">n</span><span class="p">;</span>
<span class="w">  </span><span class="kt">char</span><span class="w"> </span><span class="n">ta</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">&#39;N&#39;</span><span class="p">;</span>
<span class="w">  </span><span class="kt">char</span><span class="w"> </span><span class="n">tb</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="sc">&#39;N&#39;</span><span class="p">;</span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">1.2</span><span class="p">;</span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">beta</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">0.001</span><span class="p">;</span>

<span class="w">  </span><span class="k">struct</span><span class="w"> </span><span class="nc">timeval</span><span class="w"> </span><span class="n">start</span><span class="p">,</span><span class="n">finish</span><span class="p">;</span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">duration</span><span class="p">;</span>

<span class="w">  </span><span class="kt">double</span><span class="o">*</span><span class="w"> </span><span class="n">A</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="o">*</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">sizeofa</span><span class="p">);</span>
<span class="w">  </span><span class="kt">double</span><span class="o">*</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="o">*</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">sizeofb</span><span class="p">);</span>
<span class="w">  </span><span class="kt">double</span><span class="o">*</span><span class="w"> </span><span class="n">C</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="o">*</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">sizeofc</span><span class="p">);</span>

<span class="w">  </span><span class="n">srand</span><span class="p">((</span><span class="kt">unsigned</span><span class="p">)</span><span class="n">time</span><span class="p">(</span><span class="nb">NULL</span><span class="p">));</span>

<span class="w">  </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">sizeofa</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span>
<span class="w">    </span><span class="n">A</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="o">%</span><span class="mi">3</span><span class="o">+</span><span class="mi">1</span><span class="p">;</span><span class="c1">//(rand()%100)/10.0;</span>

<span class="w">  </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">sizeofb</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span>
<span class="w">    </span><span class="n">B</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="o">%</span><span class="mi">3</span><span class="o">+</span><span class="mi">1</span><span class="p">;</span><span class="c1">//(rand()%100)/10.0;</span>

<span class="w">  </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">&lt;</span><span class="n">sizeofc</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span>
<span class="w">    </span><span class="n">C</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">i</span><span class="o">%</span><span class="mi">3</span><span class="o">+</span><span class="mi">1</span><span class="p">;</span><span class="c1">//(rand()%100)/10.0;</span>
<span class="w">  </span><span class="c1">//#if 0</span>
<span class="w">  </span><span class="n">printf</span><span class="p">(</span><span class="s">&quot;m=%d,n=%d,k=%d,alpha=%lf,beta=%lf,sizeofc=%d</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">,</span><span class="n">k</span><span class="p">,</span><span class="n">alpha</span><span class="p">,</span><span class="n">beta</span><span class="p">,</span><span class="n">sizeofc</span><span class="p">);</span>
<span class="w">  </span><span class="n">gettimeofday</span><span class="p">(</span><span class="o">&amp;</span><span class="n">start</span><span class="p">,</span><span class="w"> </span><span class="nb">NULL</span><span class="p">);</span>
<span class="w">  </span><span class="n">dgemm_</span><span class="p">(</span><span class="o">&amp;</span><span class="n">ta</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">tb</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">alpha</span><span class="p">,</span><span class="w"> </span><span class="n">A</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">beta</span><span class="p">,</span><span class="w"> </span><span class="n">C</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">m</span><span class="p">);</span>
<span class="w">  </span><span class="n">gettimeofday</span><span class="p">(</span><span class="o">&amp;</span><span class="n">finish</span><span class="p">,</span><span class="w"> </span><span class="nb">NULL</span><span class="p">);</span>

<span class="w">  </span><span class="n">duration</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">((</span><span class="kt">double</span><span class="p">)(</span><span class="n">finish</span><span class="p">.</span><span class="n">tv_sec</span><span class="o">-</span><span class="n">start</span><span class="p">.</span><span class="n">tv_sec</span><span class="p">)</span><span class="o">*</span><span class="mi">1000000</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="p">)(</span><span class="n">finish</span><span class="p">.</span><span class="n">tv_usec</span><span class="o">-</span><span class="n">start</span><span class="p">.</span><span class="n">tv_usec</span><span class="p">))</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mi">1000000</span><span class="p">;</span>
<span class="w">  </span><span class="kt">double</span><span class="w"> </span><span class="n">gflops</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mf">2.0</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">m</span><span class="w"> </span><span class="o">*</span><span class="n">n</span><span class="o">*</span><span class="n">k</span><span class="p">;</span>
<span class="w">  </span><span class="n">gflops</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">gflops</span><span class="o">/</span><span class="n">duration</span><span class="o">*</span><span class="mf">1.0e-6</span><span class="p">;</span>

<span class="w">  </span><span class="kt">FILE</span><span class="w"> </span><span class="o">*</span><span class="n">fp</span><span class="p">;</span>
<span class="w">  </span><span class="n">fp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fopen</span><span class="p">(</span><span class="s">&quot;timeDGEMM.txt&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;a&quot;</span><span class="p">);</span>
<span class="w">  </span><span class="n">fprintf</span><span class="p">(</span><span class="n">fp</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;%dx%dx%d</span><span class="se">\t</span><span class="s">%lf s</span><span class="se">\t</span><span class="s">%lf MFLOPS</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">k</span><span class="p">,</span><span class="w"> </span><span class="n">duration</span><span class="p">,</span><span class="w"> </span><span class="n">gflops</span><span class="p">);</span>
<span class="w">  </span><span class="n">fclose</span><span class="p">(</span><span class="n">fp</span><span class="p">);</span>

<span class="w">  </span><span class="n">free</span><span class="p">(</span><span class="n">A</span><span class="p">);</span>
<span class="w">  </span><span class="n">free</span><span class="p">(</span><span class="n">B</span><span class="p">);</span>
<span class="w">  </span><span class="n">free</span><span class="p">(</span><span class="n">C</span><span class="p">);</span>
<span class="w">  </span><span class="k">return</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
<div class="highlight"><pre><span></span><code>gcc -o time_dgemm time_dgemm.c /your/path/libopenblas.a -lpthread
./time_dgemm &lt;m&gt; &lt;n&gt; &lt;k&gt;
</code></pre></div>
<h2 id="troubleshooting">Troubleshooting</h2>
<ul>
<li>Please read <a href="../faq/">Faq</a> at first.</li>
<li>Please use gcc version 4.6 and above to compile Sandy Bridge AVX kernels on Linux/MingW/BSD.</li>
<li>Please use Clang version 3.1 and above to compile the library on Sandy Bridge microarchitecture. The Clang 3.0 will generate the wrong AVX binary code.</li>
<li>The number of CPUs/Cores should less than or equal to 256. On Linux x86_64(amd64), there is experimental support for up to 1024 CPUs/Cores and 128 numa nodes if you build the library with BIGNUMA=1.</li>
<li>OpenBLAS does not set processor affinity by default. On Linux, you can enable processor affinity by commenting the line NO_AFFINITY=1 in Makefile.rule. But this may cause <a href="https://stat.ethz.ch/pipermail/r-sig-hpc/2012-April/001348.html">the conflict with R parallel</a>.</li>
<li>On Loongson 3A. make test would be failed because of pthread_create error. The error code is EAGAIN. However, it will be OK when you run the same testcase on shell.</li>
</ul>
<h2 id="blas-reference-manual">BLAS reference manual</h2>
<p>If you want to understand every BLAS function and definition, please read <a href="https://software.intel.com/en-us/intel-mkl/documentation">Intel MKL reference manual</a> or <a href="http://netlib.org/blas/">netlib.org</a></p>
<p>Here are <a href="../extensions/">OpenBLAS extension functions</a></p>


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