HashedWDFeatures.cpp

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00001 /*
00002  * This program is free software; you can redistribute it and/or modify
00003  * it under the terms of the GNU General Public License as published by
00004  * the Free Software Foundation; either version 3 of the License, or
00005  * (at your option) any later version.
00006  *
00007  * Written (W) 2010 Soeren Sonnenburg
00008  * Copyright (C) 2010 Berlin Institute of Technology
00009  */
00010 
00011 #include <shogun/features/HashedWDFeatures.h>
00012 #include <shogun/io/SGIO.h>
00013 
00014 using namespace shogun;
00015 
00016 CHashedWDFeatures::CHashedWDFeatures() :CDotFeatures()
00017 {
00018     SG_UNSTABLE("CHashedWDFeatures::CHashedWDFeatures()", "\n");
00019 
00020     strings = NULL;
00021 
00022     degree = 0;
00023     start_degree = 0;
00024     from_degree = 0;
00025     string_length = 0;
00026     num_strings = 0;
00027     alphabet_size = 0;
00028     w_dim = 0;
00029     partial_w_dim = 0;
00030     wd_weights = NULL;
00031     mask = 0;
00032     m_hash_bits = 0;
00033 
00034     normalization_const = 0.0;
00035 }
00036 
00037 CHashedWDFeatures::CHashedWDFeatures(CStringFeatures<uint8_t>* str,
00038         int32_t start_order, int32_t order, int32_t from_order,
00039         int32_t hash_bits) : CDotFeatures()
00040 {
00041     ASSERT(start_order>=0);
00042     ASSERT(start_order<order);
00043     ASSERT(order<=from_order);
00044     ASSERT(hash_bits>0);
00045     ASSERT(str);
00046     ASSERT(str->have_same_length());
00047     SG_REF(str);
00048 
00049     strings=str;
00050     string_length=str->get_max_vector_length();
00051     num_strings=str->get_num_vectors();
00052     CAlphabet* alpha=str->get_alphabet();
00053     alphabet_size=alpha->get_num_symbols();
00054     SG_UNREF(alpha);
00055 
00056     degree=order;
00057     start_degree=start_order;
00058     from_degree=from_order;
00059     m_hash_bits=hash_bits;
00060     set_wd_weights();
00061     set_normalization_const();
00062 }
00063 
00064 CHashedWDFeatures::CHashedWDFeatures(const CHashedWDFeatures& orig)
00065     : CDotFeatures(orig), strings(orig.strings),
00066     degree(orig.degree), start_degree(orig.start_degree), 
00067     from_degree(orig.from_degree), m_hash_bits(orig.m_hash_bits),
00068     normalization_const(orig.normalization_const)
00069 {
00070     SG_REF(strings);
00071     string_length=strings->get_max_vector_length();
00072     num_strings=strings->get_num_vectors();
00073     CAlphabet* alpha=strings->get_alphabet();
00074     alphabet_size=alpha->get_num_symbols();
00075     SG_UNREF(alpha);
00076 
00077     set_wd_weights();
00078 }
00079 
00080 CHashedWDFeatures::~CHashedWDFeatures()
00081 {
00082     SG_UNREF(strings);
00083     SG_FREE(wd_weights);
00084 }
00085 
00086 float64_t CHashedWDFeatures::dot(int32_t vec_idx1, CDotFeatures* df, int32_t vec_idx2)
00087 {
00088     ASSERT(df);
00089     ASSERT(df->get_feature_type() == get_feature_type());
00090     ASSERT(df->get_feature_class() == get_feature_class());
00091     CHashedWDFeatures* wdf = (CHashedWDFeatures*) df;
00092 
00093     int32_t len1, len2;
00094     bool free_vec1, free_vec2;
00095 
00096     uint8_t* vec1=strings->get_feature_vector(vec_idx1, len1, free_vec1);
00097     uint8_t* vec2=wdf->strings->get_feature_vector(vec_idx2, len2, free_vec2);
00098 
00099     ASSERT(len1==len2);
00100 
00101     float64_t sum=0.0;
00102 
00103     for (int32_t i=0; i<len1; i++)
00104     {
00105         for (int32_t j=0; (i+j<len1) && (j<degree); j++)
00106         {
00107             if (vec1[i+j]!=vec2[i+j])
00108                 break;
00109             if (j>=start_degree)
00110                 sum += wd_weights[j]*wd_weights[j];
00111         }
00112     }
00113     strings->free_feature_vector(vec1, vec_idx1, free_vec1);
00114     wdf->strings->free_feature_vector(vec2, vec_idx2, free_vec2);
00115     return sum/CMath::sq(normalization_const);
00116 }
00117 
00118 float64_t CHashedWDFeatures::dense_dot(int32_t vec_idx1, const float64_t* vec2, int32_t vec2_len)
00119 {
00120     if (vec2_len != w_dim)
00121         SG_ERROR("Dimensions don't match, vec2_dim=%d, w_dim=%d\n", vec2_len, w_dim);
00122 
00123     float64_t sum=0;
00124     int32_t lim=CMath::min(degree, string_length);
00125     int32_t len;
00126     bool free_vec1;
00127     uint8_t* vec = strings->get_feature_vector(vec_idx1, len, free_vec1);
00128     uint32_t* val=SG_MALLOC(uint32_t, len);
00129 
00130     uint32_t offs=0;
00131 
00132     if (start_degree>0)
00133     {
00134         // compute hash for strings of length start_degree-1
00135         for (int32_t i=0; i+start_degree < len; i++) 
00136             val[i]=CHash::MurmurHash2(&vec[i], start_degree, 0xDEADBEAF);
00137     }
00138     else
00139         CMath::fill_vector(val, len, 0xDEADBEAF);
00140 
00141     for (int32_t k=start_degree; k<lim; k++)
00142     {
00143         float64_t wd = wd_weights[k];
00144 
00145         uint32_t o=offs;
00146         for (int32_t i=0; i+k < len; i++) 
00147         {
00148             const uint32_t h=CHash::IncrementalMurmurHash2(vec[i+k], val[i]);
00149             val[i]=h;
00150 #ifdef DEBUG_HASHEDWD
00151             SG_PRINT("vec[i]=%d, k=%d, offs=%d o=%d h=%d \n", vec[i], k,offs, o, h);
00152 #endif
00153             sum+=vec2[o+(h & mask)]*wd;
00154             o+=partial_w_dim;
00155         }
00156         offs+=partial_w_dim*len;
00157     }
00158     SG_FREE(val);
00159     strings->free_feature_vector(vec, vec_idx1, free_vec1);
00160 
00161     return sum/normalization_const;
00162 }
00163 
00164 void CHashedWDFeatures::add_to_dense_vec(float64_t alpha, int32_t vec_idx1, float64_t* vec2, int32_t vec2_len, bool abs_val)
00165 {
00166     if (vec2_len != w_dim)
00167         SG_ERROR("Dimensions don't match, vec2_dim=%d, w_dim=%d\n", vec2_len, w_dim);
00168 
00169     int32_t lim=CMath::min(degree, string_length);
00170     int32_t len;
00171     bool free_vec1;
00172     uint8_t* vec = strings->get_feature_vector(vec_idx1, len, free_vec1);
00173     uint32_t* val=SG_MALLOC(uint32_t, len);
00174 
00175     uint32_t offs=0;
00176 
00177     if (start_degree>0)
00178     {
00179         // compute hash for strings of length start_degree-1
00180         for (int32_t i=0; i+start_degree < len; i++) 
00181             val[i]=CHash::MurmurHash2(&vec[i], start_degree, 0xDEADBEAF);
00182     }
00183     else
00184         CMath::fill_vector(val, len, 0xDEADBEAF);
00185 
00186     for (int32_t k=start_degree; k<lim; k++)
00187     {
00188         float64_t wd = alpha*wd_weights[k]/normalization_const;
00189 
00190         if (abs_val)
00191             wd=CMath::abs(wd);
00192 
00193         uint32_t o=offs;
00194         for (int32_t i=0; i+k < len; i++) 
00195         {
00196             const uint32_t h=CHash::IncrementalMurmurHash2(vec[i+k], val[i]);
00197             val[i]=h;
00198 
00199 #ifdef DEBUG_HASHEDWD
00200             SG_PRINT("offs=%d o=%d h=%d \n", offs, o, h);
00201             SG_PRINT("vec[i]=%d, k=%d, offs=%d o=%d h=%d \n", vec[i], k,offs, o, h);
00202 #endif
00203             vec2[o+(h & mask)]+=wd;
00204             o+=partial_w_dim;
00205         }
00206         offs+=partial_w_dim*len;
00207     }
00208 
00209     SG_FREE(val);
00210     strings->free_feature_vector(vec, vec_idx1, free_vec1);
00211 }
00212 
00213 void CHashedWDFeatures::set_wd_weights()
00214 {
00215     ASSERT(degree>0);
00216 
00217     mask=(uint32_t) (((uint64_t) 1)<<m_hash_bits)-1;
00218     partial_w_dim=1<<m_hash_bits;
00219     w_dim=partial_w_dim*string_length*(degree-start_degree);
00220 
00221     wd_weights=SG_MALLOC(float64_t, degree);
00222 
00223     for (int32_t i=0; i<degree; i++)
00224         wd_weights[i]=sqrt(2.0*(from_degree-i)/(from_degree*(from_degree+1)));
00225 
00226     SG_DEBUG("created HashedWDFeatures with d=%d (%d), alphabetsize=%d, "
00227             "dim=%d partial_dim=%d num=%d, len=%d\n", 
00228             degree, from_degree, alphabet_size, 
00229             w_dim, partial_w_dim, num_strings, string_length);
00230 }
00231 
00232 
00233 void CHashedWDFeatures::set_normalization_const(float64_t n)
00234 {
00235     if (n==0)
00236     {
00237         normalization_const=0;
00238         for (int32_t i=0; i<degree; i++)
00239             normalization_const+=(string_length-i)*wd_weights[i]*wd_weights[i];
00240 
00241         normalization_const=CMath::sqrt(normalization_const);
00242     }
00243     else
00244         normalization_const=n;
00245 
00246     SG_DEBUG("normalization_const:%f\n", normalization_const);
00247 }
00248 
00249 CFeatures* CHashedWDFeatures::duplicate() const
00250 {
00251     return new CHashedWDFeatures(*this);
00252 }
00253 
00254 
00255 int32_t CHashedWDFeatures::get_nnz_features_for_vector(int32_t num)
00256 {
00257     int32_t vlen=-1;
00258     bool free_vec;
00259     uint8_t* vec=strings->get_feature_vector(num, vlen, free_vec);
00260     strings->free_feature_vector(vec, num, free_vec);
00261     return degree*vlen;
00262 }
00263 
00264 void* CHashedWDFeatures::get_feature_iterator(int32_t vector_index)
00265 {
00266     SG_NOTIMPLEMENTED;
00267     return NULL;
00268 }
00269 
00270 bool CHashedWDFeatures::get_next_feature(int32_t& index, float64_t& value,
00271         void* iterator)
00272 {
00273     SG_NOTIMPLEMENTED;
00274     return NULL;
00275 }
00276 
00277 void CHashedWDFeatures::free_feature_iterator(void* iterator)
00278 {
00279     SG_NOTIMPLEMENTED;
00280 }
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