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| 34 | <li><a href="../index.html">COIN-OR Home</a></li> |
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| 35 | <li><a href="index.html">CLP Home</a></li> |
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| 36 | <li><a href="documentation.html">CLP Documentation</a></li> |
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| 37 | <li><a href="faq.html">CLP FAQ</a></li> |
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| 38 | </ul> |
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| 41 | </TD> |
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| 42 | <!-- --> |
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| 43 | <!-- MAIN CONTENT --> |
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| 44 | <!-- --> |
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| 45 | <td> |
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| 46 | <div class="main-content"> |
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| 47 | |
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| 48 | <!-- DO NOT CHANGE THIS FAQ by hand. The content is automatically generated |
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| 49 | via DocBook. The source is in COIN/Clp/Docs. Read the DocBook for CLP |
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| 50 | document for more info. |
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| 51 | --> |
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| 52 | |
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| 53 | <!-- --> |
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| 54 | <!-- Begin DocBook content here --> |
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| 55 | <!-- --> |
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| 56 | <div class="qandaset"><dl><dt>Q: <a href="#id4693599"> |
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| 57 | What is CLP? |
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| 58 | </a></dt><dt>Q: <a href="#id4694311"> |
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| 59 | What are some of the features of CLP? |
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| 60 | </a></dt><dt>Q: <a href="#id4694338"> |
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| 61 | How do I obtain and install CLP? |
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| 62 | </a></dt><dt>Q: <a href="#id4695264"> |
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| 63 | Is CLP reliable? |
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| 64 | </a></dt><dt>Q: <a href="#id4695295"> |
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| 65 | On which platforms does CLP run? |
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| 66 | </a></dt><dt>Q: <a href="#id4695346"> |
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| 67 | Is there any documentation for CLP? |
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| 68 | </a></dt><dt>Q: <a href="#id4757343"> |
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| 69 | Is CLP as fast as OSL? |
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| 70 | </a></dt><dt>Q: <a href="#id4757364"> |
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| 71 | When will version 1.0 of CLP be available? |
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| 72 | </a></dt><dt>Q: <a href="#id4757396"> |
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| 73 | The barrier method sounds interesting, what are some of the details? |
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| 74 | </a></dt><dt>Q: <a href="#id4757421"> |
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| 75 | Which Cholesky factorizations codes are supported by CLP's barrier method? |
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| 76 | </a></dt><dt>Q: <a href="#id4757485"> |
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| 77 | When will CLP have a good native ordering? |
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| 78 | </a></dt><dt>Q: <a href="#id4757506"> |
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| 79 | Is the barrier code as mature as the simplex code? |
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| 80 | </a></dt><dt>Q: <a href="#id4757531"> |
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| 81 | Which algorithm should I use for quadratic programming and should I keep an |
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| 82 | eye open for any issues? |
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| 83 | </a></dt><dt>Q: <a href="#id4757563"> |
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| 84 | What can the community do to help? |
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| 85 | </a></dt></dl><table border="0" summary="Q and A Set"><col align="left" width="1%"><tbody><tr class="question"><td align="left" valign="top"><a name="id4693599"></a><a name="id4693601"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 86 | What is <a href="http://www.coin-or.org/Clp/" target="_top">CLP</a>? |
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| 87 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 88 | (DN 08/27/04) The <a href="http://www.coin-or.org/" target="_top">COIN-OR</a> LP code |
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| 89 | is designed to be a high quality Simplex code provided under the terms of the |
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| 90 | <a href="http://opensource.org/licenses/cpl.php" target="_top">Common Public License</a>. |
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| 91 | CLP is written in C++, and is primarily intended to be used as a callable |
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| 92 | library (though a rudimentary stand-alone executable exists). |
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| 93 | The first release was version .90. The current release is version .99.9. |
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| 94 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4694311"></a><a name="id4694314"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 95 | What are some of the features of CLP? |
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| 96 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 97 | (DN 08/27/04) CLP includes primal and dual Simplex solvers. Both dual and primal algorithms |
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| 98 | can use matrix storage methods provided by the user (0-1 and network matrices |
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| 99 | are already supported in addition to the default sparse matrix). The dual algorithm |
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| 100 | has Dantzig and Steepest edge row pivot choices; new ones may be provided by |
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| 101 | the user. The same is true for the column pivot choice of the primal algorithm. |
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| 102 | The primal can also use a non linear cost which should work for piecewise |
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| 103 | linear convex functions. CLP also includes a barrier method for solving LPs. |
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| 104 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4694338"></a><a name="id4694340"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 105 | How do I obtain and install CLP? |
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| 106 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 107 | (DN 08/27/04) Please see the |
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| 108 | <a href="http://www.coin-or.org/faqs.html" target="_top">COIN-OR FAQ</a> |
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| 109 | for details on how to |
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| 110 | <a href="http://www.coin-or.org/faqs.html#ObtainSrcCode" target="_top">obtain</a> |
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| 111 | and |
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| 112 | <a href="http://www.coin-or.org/faqs.html#BuildCode" target="_top">install</a> |
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| 113 | COIN-OR modules. |
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| 114 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4695264"></a><a name="id4695266"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 115 | Is CLP reliable? |
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| 116 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 117 | (DN 09/07/04) CLP has been tested on many problems of up to 1.5 million |
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| 118 | constraints and has shown itself as reliable as OSL. It is also being tested |
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| 119 | in the context of |
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| 120 | SBB |
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| 121 | ("Simple Branch and Bound", which is used to solve integer |
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| 122 | programs), but more testing is needed before it can get to version 1.0. |
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| 123 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4695295"></a><a name="id4695297"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 124 | On which platforms does CLP run? |
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| 125 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 126 | (DN 08/27/04) CLP compiles and has been tested (to varying degrees) on the following |
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| 127 | platforms: |
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| 128 | </p><div class="itemizedlist"><ul type="disc"><li><p> |
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| 129 | Linux using g++ version 3.1.1 (or later) |
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| 130 | </p></li><li><p> |
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| 131 | Windows using Microsoft Visual C++ 6 |
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| 132 | </p></li><li><p> |
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| 133 | Windows using cygwin |
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| 134 | </p></li><li><p> |
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| 135 | AIX using xIC (not supported in the current Makefile) |
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| 136 | </p></li></ul></div></td></tr><tr class="question"><td align="left" valign="top"><a name="id4695346"></a><a name="id4695348"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 137 | Is there any documentation for CLP? |
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| 138 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 139 | (DN 09/16/04) An early release of a User Guide is available on the |
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| 140 | <a href="http://www.coin-or.org/Clp/documentation.html" target="_top">CLP documentation webpage</a>. |
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| 141 | Also available is a list of |
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| 142 | <a href="http://www.coin-or.org/Doxygen/Clp/" target="_top">CLP class descriptions</a> generated |
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| 143 | by <a href="http://www.doxygen.org" target="_top">Doxygen</a>. |
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| 144 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757343"></a><a name="id4757346"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 145 | Is CLP as fast as OSL? |
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| 146 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 147 | (DN 08/27/04) CLP uses sparse matrix techniques designed for very large |
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| 148 | problems. The design criteria were for it not to be too slow. Some speed |
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| 149 | has been sacrificed to make the code less opaque OSL (not difficult!). |
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| 150 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757364"></a><a name="id4757366"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 151 | When will version 1.0 of CLP be available? |
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| 152 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 153 | (DN 08/27/04) It is expected that version 1.0 will be released in time for the 2004 |
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| 154 | <a href="http://www.informs.org" target="_top">INFORMS</a> |
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| 155 | <a href="http://www.informs.org/Conf/Denver2004/" target="_top">Annual Meeting</a> |
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| 156 | (24-27 October, 2004). |
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| 157 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757396"></a><a name="id4757398"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 158 | The barrier method sounds interesting, what are some of the details? |
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| 159 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 160 | (DN 08/30/04) The CLP barrier method solves convex QPs as well as LPs. In |
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| 161 | general, a barrier method requires implementation of the algorithm, as |
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| 162 | well as a fast Cholesky factorization. CLP provides the algorithm, and is |
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| 163 | expected to have a reasonable factorization implementation by the release of |
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| 164 | CLP version 1.0. However, the sparse factorization requires a good ordering |
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| 165 | algorithm, which the user is expected to provide (perhaps a better |
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| 166 | factorization code as well). |
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| 167 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757421"></a><a name="id4757423"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 168 | Which Cholesky factorizations codes are supported by CLP's barrier method? |
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| 169 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 170 | (DN 09/16/04) The Cholesky interface is flexible enough so that a variety of Cholesky |
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| 171 | ordering and factorization codes can be used. Interfaces are provided to each |
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| 172 | of the following: |
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| 173 | </p><div class="itemizedlist"><ul type="disc"><li><p> |
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| 174 | Anshul Gupta's WSSMP parallel enabled ordering and factorization code |
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| 175 | </p></li><li><p> |
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| 176 | Sivan Toledo's TAUCS parallel enabled factorization code (the package includes |
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| 177 | third party ordering codes) |
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| 178 | </p></li><li><p> |
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| 179 | University of Florida's Approximate Minimum Degree (AMD) ordering code (the |
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| 180 | CLP native factorization code is used with this ordering code) |
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| 181 | </p></li><li><p> |
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| 182 | CLP native code: very weak ordering but competitive nonparallel factorization |
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| 183 | </p></li><li><p> |
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| 184 | Fast dense factorization |
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| 185 | </p></li></ul></div><p> |
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| 186 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757485"></a><a name="id4757487"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 187 | When will CLP have a good native ordering? |
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| 188 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 189 | (DN 09/16/04) The best outcome would be to have an existing ordering code available as part |
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| 190 | of the COIN distribution under the CPL. However, if this is not possible, the |
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| 191 | native ordering will be made respectable. |
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| 192 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757506"></a><a name="id4757508"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 193 | Is the barrier code as mature as the simplex code? |
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| 194 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 195 | (DN 09/16/04) The simplex code has been exposed to user testing for more than a year and |
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| 196 | and the principal author, John Forrest, knows more about simplex algorithms |
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| 197 | than interior point algorithms, so the answer is "no". However, it |
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| 198 | performs well on test sets and seems to be more reliable than some |
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| 199 | commercially available codes (including OSL). |
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| 200 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757531"></a><a name="id4757533"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 201 | Which algorithm should I use for quadratic programming and should I keep an |
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| 202 | eye open for any issues? |
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| 203 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 204 | (DN 09/16/04) The interior point algorithm for quadratic programming is much more elegant |
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| 205 | and normally much faster than the quadratic simplex code. Caution is |
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| 206 | suggested with the presolve as not all bugs have been found and squashed when |
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| 207 | a quadratic objective is used. One may wish to switch off the crossover to a |
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| 208 | basic feasible solution as the simplex code can be slow. The sequential |
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| 209 | linear code is useful as a "crash" to the simplex code; its |
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| 210 | convergence is poor but, say, 100 iterations could set up the problem well for |
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| 211 | the simplex code. |
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| 212 | </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id4757563"></a><a name="id4757565"></a><b>Q:</b></td><td align="left" valign="top"><p> |
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| 213 | What can the community do to help? |
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| 214 | </p></td></tr><tr class="answer"><td align="left" valign="top"><b>A:</b></td><td align="left" valign="top"><p> |
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| 215 | (DN 09/09/04) A lot! A good first step would be to join the CLP |
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| 216 | <a href="http://www.coin-or.org/mail.html" target="_top">mailing lists</a>. Some |
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| 217 | other possibilities: |
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| 218 | </p><div class="itemizedlist"><ul type="disc"><li><p> |
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| 219 | Comment on the design |
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| 220 | </p></li><li><p> |
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| 221 | Break the code, or better yet, mend it. |
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| 222 | </p></li><li><p> |
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| 223 | Add non-English language support in your own favo(u)rite language. |
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| 224 | </p></li><li><p> |
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| 225 | Improve the CLP executable. In particular it would be nice to be able to link |
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| 226 | the executable's online help system with the existing CLP Samples (e.g. entering |
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| 227 | <b class="userinput"><tt>presol???</tt></b> would give the user references to all |
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| 228 | CLP Sample files which use presolve). |
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| 229 | </p></li><li><p> |
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| 230 | Implement a dual Simplex method for QPs (quadratic programs) |
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| 231 | </p></li><li><p> |
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| 232 | Implement a parametric Simplex method |
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| 233 | </p></li><li><p> |
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| 234 | Implement a true network Simplex method (network matrix and factorization |
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| 235 | are already in place, but the method is not) |
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| 236 | </p></li><li><p> |
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| 237 | Fill the holes in the barrier method mentioned above. |
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| 238 | </p></li></ul></div></td></tr></tbody></table></div> |
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| 239 | |
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