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<div class="title">/usr/local/google/home/jbreiden/tesseract-ocr-read-only/ccstruct/dppoint.cpp</div> </div>
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<a href="a00744.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/**********************************************************************</span>
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<a name="l00002"></a>00002 <span class="comment"> * File: dppoint.cpp</span>
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<a name="l00003"></a>00003 <span class="comment"> * Description: Simple generic dynamic programming class.</span>
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<a name="l00004"></a>00004 <span class="comment"> * Author: Ray Smith</span>
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<a name="l00005"></a>00005 <span class="comment"> * Created: Wed Mar 25 19:08:01 PDT 2009</span>
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<a name="l00006"></a>00006 <span class="comment"> *</span>
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<a name="l00007"></a>00007 <span class="comment"> * (C) Copyright 2009, Google Inc.</span>
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<a name="l00008"></a>00008 <span class="comment"> ** Licensed under the Apache License, Version 2.0 (the "License");</span>
111
<a name="l00009"></a>00009 <span class="comment"> ** you may not use this file except in compliance with the License.</span>
112
<a name="l00010"></a>00010 <span class="comment"> ** You may obtain a copy of the License at</span>
113
<a name="l00011"></a>00011 <span class="comment"> ** http://www.apache.org/licenses/LICENSE-2.0</span>
114
<a name="l00012"></a>00012 <span class="comment"> ** Unless required by applicable law or agreed to in writing, software</span>
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<a name="l00013"></a>00013 <span class="comment"> ** distributed under the License is distributed on an "AS IS" BASIS,</span>
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<a name="l00014"></a>00014 <span class="comment"> ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span>
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<a name="l00015"></a>00015 <span class="comment"> ** See the License for the specific language governing permissions and</span>
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<a name="l00016"></a>00016 <span class="comment"> ** limitations under the License.</span>
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<a name="l00017"></a>00017 <span class="comment"> *</span>
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<a name="l00018"></a>00018 <span class="comment"> **********************************************************************/</span>
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<a name="l00019"></a>00019
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<a name="l00020"></a>00020 <span class="preprocessor">#include "<a class="code" href="a00745.html">dppoint.h</a>"</span>
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<a name="l00021"></a>00021 <span class="preprocessor">#include "<a class="code" href="a00860.html">tprintf.h</a>"</span>
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<a name="l00022"></a>00022
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<a name="l00023"></a>00023 <span class="keyword">namespace </span><a class="code" href="a01266.html#afed58feacb84df2de88bdd613cfdba6d">tesseract</a> {
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<a name="l00024"></a>00024
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<a name="l00025"></a>00025 <span class="comment">// Solve the dynamic programming problem for the given array of points, with</span>
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<a name="l00026"></a>00026 <span class="comment">// the given size and cost function.</span>
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<a name="l00027"></a>00027 <span class="comment">// Steps backwards are limited to being between min_step and max_step</span>
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<a name="l00028"></a>00028 <span class="comment">// inclusive.</span>
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<a name="l00029"></a>00029 <span class="comment">// The return value is the tail of the best path.</span>
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<a name="l00030"></a><a class="code" href="a00359.html#a9d0050679afe827f7e0434c70916a07a">00030</a> <a class="code" href="a00359.html">DPPoint</a>* <a class="code" href="a00359.html#a9d0050679afe827f7e0434c70916a07a">DPPoint::Solve</a>(<span class="keywordtype">int</span> min_step, <span class="keywordtype">int</span> max_step, <span class="keywordtype">bool</span> debug,
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<a name="l00031"></a>00031 CostFunc cost_func, <span class="keywordtype">int</span> size, <a class="code" href="a00359.html">DPPoint</a>* points) {
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<a name="l00032"></a>00032 <span class="keywordflow">if</span> (size <= 0 || max_step < min_step || min_step >= size)
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<a name="l00033"></a>00033 <span class="keywordflow">return</span> NULL; <span class="comment">// Degenerate, but not necessarily an error.</span>
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<a name="l00034"></a>00034 <a class="code" href="a00823.html#a93a603f4063a6b9403d81caa245a583b">ASSERT_HOST</a>(min_step > 0); <span class="comment">// Infinite loop possible if this is not true.</span>
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<a name="l00035"></a>00035 <span class="keywordflow">if</span> (debug)
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<a name="l00036"></a>00036 <a class="code" href="a00860.html#a02aa7cca2c3857c14716e8cca96ace6c">tprintf</a>(<span class="stringliteral">"min = %d, max=%d\n"</span>,
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<a name="l00037"></a>00037 min_step, max_step);
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<a name="l00038"></a>00038 <span class="comment">// Evaluate the total cost at each point.</span>
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<a name="l00039"></a>00039 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i < size; ++i) {
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<a name="l00040"></a>00040 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> offset = min_step; offset <= max_step; ++offset) {
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<a name="l00041"></a>00041 <a class="code" href="a00359.html">DPPoint</a>* prev = offset <= i ? points + i - offset : NULL;
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<a name="l00042"></a>00042 <a class="code" href="a00831.html#ac53c9cafaf7fe16f985994c49f6b0964">inT64</a> new_cost = (points[i].*cost_func)(prev);
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<a name="l00043"></a>00043 <span class="keywordflow">if</span> (points[i].best_prev_ != NULL && offset > min_step * 2 &&
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<a name="l00044"></a>00044 new_cost > points[i].total_cost_)
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<a name="l00045"></a>00045 <span class="keywordflow">break</span>; <span class="comment">// Find only the first minimum if going over twice the min.</span>
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<a name="l00046"></a>00046 }
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<a name="l00047"></a>00047 points[i].total_cost_ += points[i].local_cost_;
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<a name="l00048"></a>00048 <span class="keywordflow">if</span> (debug) {
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<a name="l00049"></a>00049 <a class="code" href="a00860.html#a02aa7cca2c3857c14716e8cca96ace6c">tprintf</a>(<span class="stringliteral">"At point %d, local cost=%d, total_cost=%d, steps=%d\n"</span>,
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<a name="l00050"></a>00050 i, points[i].local_cost_, points[i].total_cost_,
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<a name="l00051"></a>00051 points[i].total_steps_);
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<a name="l00052"></a>00052 }
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<a name="l00053"></a>00053 }
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<a name="l00054"></a>00054 <span class="comment">// Now find the end of the best path and return it.</span>
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<a name="l00055"></a>00055 <span class="keywordtype">int</span> best_cost = points[size - 1].total_cost_;
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<a name="l00056"></a>00056 <span class="keywordtype">int</span> best_end = size - 1;
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<a name="l00057"></a>00057 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> end = best_end - 1; end >= size - min_step; --end) {
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<a name="l00058"></a>00058 <span class="keywordtype">int</span> cost = points[end].total_cost_;
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<a name="l00059"></a>00059 <span class="keywordflow">if</span> (cost < best_cost) {
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<a name="l00060"></a>00060 best_cost = cost;
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<a name="l00061"></a>00061 best_end = end;
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<a name="l00062"></a>00062 }
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<a name="l00063"></a>00063 }
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<a name="l00064"></a>00064 <span class="keywordflow">return</span> points + best_end;
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<a name="l00065"></a>00065 }
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<a name="l00066"></a>00066
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<a name="l00067"></a>00067 <span class="comment">// A CostFunc that takes the variance of step into account in the cost.</span>
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<a name="l00068"></a><a class="code" href="a00359.html#a4d01fa4702020ea2e3cbd89f754fc9e5">00068</a> <a class="code" href="a00831.html#ac53c9cafaf7fe16f985994c49f6b0964">inT64</a> <a class="code" href="a00359.html#a4d01fa4702020ea2e3cbd89f754fc9e5">DPPoint::CostWithVariance</a>(<span class="keyword">const</span> <a class="code" href="a00359.html">DPPoint</a>* prev) {
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<a name="l00069"></a>00069 <span class="keywordflow">if</span> (prev == NULL || prev == <span class="keyword">this</span>) {
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<a name="l00070"></a>00070 UpdateIfBetter(0, 1, NULL, 0, 0, 0);
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<a name="l00071"></a>00071 <span class="keywordflow">return</span> 0;
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<a name="l00072"></a>00072 }
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<a name="l00073"></a>00073
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<a name="l00074"></a>00074 <span class="keywordtype">int</span> delta = <span class="keyword">this</span> - prev;
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<a name="l00075"></a>00075 <a class="code" href="a00831.html#aba1f582fd0168f3ff9225d8c90fa9eb8">inT32</a> n = prev->n_ + 1;
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<a name="l00076"></a>00076 <a class="code" href="a00831.html#aba1f582fd0168f3ff9225d8c90fa9eb8">inT32</a> sig_x = prev->sig_x_ + delta;
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<a name="l00077"></a>00077 <a class="code" href="a00831.html#ac53c9cafaf7fe16f985994c49f6b0964">inT64</a> sig_xsq = prev->sig_xsq_ + delta * delta;
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<a name="l00078"></a>00078 <a class="code" href="a00831.html#ac53c9cafaf7fe16f985994c49f6b0964">inT64</a> cost = (sig_xsq - sig_x * sig_x / n) / n;
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<a name="l00079"></a>00079 cost += prev->total_cost_;
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<a name="l00080"></a>00080 UpdateIfBetter(cost, prev->total_steps_ + 1, prev, n, sig_x, sig_xsq);
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<a name="l00081"></a>00081 <span class="keywordflow">return</span> cost;
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<a name="l00082"></a>00082 }
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<a name="l00083"></a>00083
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<a name="l00084"></a>00084 <span class="comment">// Update the other members if the cost is lower.</span>
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<a name="l00085"></a>00085 <span class="keywordtype">void</span> DPPoint::UpdateIfBetter(<a class="code" href="a00831.html#ac53c9cafaf7fe16f985994c49f6b0964">inT64</a> cost, <a class="code" href="a00831.html#aba1f582fd0168f3ff9225d8c90fa9eb8">inT32</a> steps, <span class="keyword">const</span> <a class="code" href="a00359.html">DPPoint</a>* prev,
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<a name="l00086"></a>00086 <a class="code" href="a00831.html#aba1f582fd0168f3ff9225d8c90fa9eb8">inT32</a> n, <a class="code" href="a00831.html#aba1f582fd0168f3ff9225d8c90fa9eb8">inT32</a> sig_x, <a class="code" href="a00831.html#ac53c9cafaf7fe16f985994c49f6b0964">inT64</a> sig_xsq) {
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<a name="l00087"></a>00087 <span class="keywordflow">if</span> (cost < total_cost_) {
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<a name="l00088"></a>00088 total_cost_ = cost;
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<a name="l00089"></a>00089 total_steps_ = steps;
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<a name="l00090"></a>00090 best_prev_ = prev;
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<a name="l00091"></a>00091 n_ = n;
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<a name="l00092"></a>00092 sig_x_ = sig_x;
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<a name="l00093"></a>00093 sig_xsq_ = sig_xsq;
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<a name="l00094"></a>00094 }
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<a name="l00095"></a>00095 }
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<a name="l00096"></a>00096
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<a name="l00097"></a>00097 } <span class="comment">// namespace tesseract.</span>
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<a name="l00098"></a>00098
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<li class="navelem"><a class="el" href="a00744.html">dppoint.cpp</a> </li>
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