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-rw-r--r--extractor/sampler.cc36
1 files changed, 36 insertions, 0 deletions
diff --git a/extractor/sampler.cc b/extractor/sampler.cc
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+++ b/extractor/sampler.cc
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+#include "sampler.h"
+
+#include "phrase_location.h"
+#include "suffix_array.h"
+
+Sampler::Sampler(shared_ptr<SuffixArray> suffix_array, int max_samples) :
+ suffix_array(suffix_array), max_samples(max_samples) {}
+
+PhraseLocation Sampler::Sample(const PhraseLocation& location) const {
+ vector<int> sample;
+ int num_subpatterns;
+ if (location.matchings == NULL) {
+ num_subpatterns = 1;
+ int low = location.sa_low, high = location.sa_high;
+ double step = max(1.0, (double) (high - low) / max_samples);
+ for (double i = low; i < high && sample.size() < max_samples; i += step) {
+ sample.push_back(suffix_array->GetSuffix(Round(i)));
+ }
+ } else {
+ num_subpatterns = location.num_subpatterns;
+ int num_matchings = location.matchings->size() / num_subpatterns;
+ double step = max(1.0, (double) num_matchings / max_samples);
+ for (double i = 0, num_samples = 0;
+ i < num_matchings && num_samples < max_samples;
+ i += step, ++num_samples) {
+ int start = Round(i) * num_subpatterns;
+ sample.insert(sample.end(), location.matchings->begin() + start,
+ location.matchings->begin() + start + num_subpatterns);
+ }
+ }
+ return PhraseLocation(sample, num_subpatterns);
+}
+
+int Sampler::Round(double x) const {
+ return x + 0.5;
+}