path: root/lib/TH/generic/THTensorRandom.c

#ifndef TH_GENERIC_FILE
#define TH_GENERIC_FILE "generic/THTensorRandom.c"
#else

void THTensor_(random)(THTensor *self, THGenerator *_generator)
{
#if defined(TH_REAL_IS_BYTE)
  TH_TENSOR_APPLY(real, self, *self_data = (unsigned char)(THRandom_random(_generator) % (UCHAR_MAX+1)););
#elif defined(TH_REAL_IS_CHAR)
  TH_TENSOR_APPLY(real, self, *self_data = (char)(THRandom_random(_generator) % (CHAR_MAX+1)););
#elif defined(TH_REAL_IS_SHORT)
  TH_TENSOR_APPLY(real, self, *self_data = (short)(THRandom_random(_generator) % (SHRT_MAX+1)););
#elif defined(TH_REAL_IS_INT)
  TH_TENSOR_APPLY(real, self, *self_data = (int)(THRandom_random(_generator) % (INT_MAX+1UL)););
#elif defined(TH_REAL_IS_LONG)
  TH_TENSOR_APPLY(real, self, *self_data = (long)(THRandom_random(_generator) % (LONG_MAX+1UL)););
#elif defined(TH_REAL_IS_FLOAT)
  TH_TENSOR_APPLY(real, self, *self_data = (float)(THRandom_random(_generator) % ((1UL << FLT_MANT_DIG)+1)););
#elif defined(TH_REAL_IS_DOUBLE)
  TH_TENSOR_APPLY(real, self, *self_data = (double)(THRandom_random(_generator) % ((1ULL << DBL_MANT_DIG)+1)););
#else
#error "Unknown type"
#endif
}

void THTensor_(geometric)(THTensor *self, THGenerator *_generator, double p)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_geometric(_generator, p););
}

void THTensor_(bernoulli)(THTensor *self, THGenerator *_generator, double p)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_bernoulli(_generator, p););
}

void THTensor_(bernoulli_FloatTensor)(THTensor *self, THGenerator *_generator, THFloatTensor *p)
{
  TH_TENSOR_APPLY2(real, self, float, p, *self_data = (real)THRandom_bernoulli(_generator, (double)*p_data););
}

void THTensor_(bernoulli_DoubleTensor)(THTensor *self, THGenerator *_generator, THDoubleTensor *p)
{
  TH_TENSOR_APPLY2(real, self, double, p, *self_data = (real)THRandom_bernoulli(_generator, (double)*p_data););
}

#if defined(TH_REAL_IS_FLOAT) || defined(TH_REAL_IS_DOUBLE)

void THTensor_(uniform)(THTensor *self, THGenerator *_generator, double a, double b)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_uniform(_generator, a, b););
}

void THTensor_(normal)(THTensor *self, THGenerator *_generator, double mean, double stdv)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_normal(_generator, mean, stdv););
}

void THTensor_(normal_means)(THTensor *self, THGenerator *gen, THTensor *means, double stddev)
{
  THTensor_(resizeAs)(self, means);
  THTensor_(normal)(self, gen, 0, stddev);
  THTensor_(cadd)(self, self, 1, means);
}

void THTensor_(normal_stddevs)(THTensor *self, THGenerator *gen, double mean, THTensor *stddevs)
{
  THTensor_(resizeAs)(self, stddevs);
  THTensor_(normal)(self, gen, 0, 1);
  THTensor_(cmul)(self, self, stddevs);
  THTensor_(add)(self, self, mean);
}

void THTensor_(normal_means_stddevs)(THTensor *self, THGenerator *gen, THTensor *means, THTensor *stddevs)
{
  THTensor_(resizeAs)(self, means);
  THTensor_(normal)(self, gen, 0, 1);
  THTensor_(cmul)(self, self, stddevs);
  THTensor_(cadd)(self, self, 1, means);
}

void THTensor_(exponential)(THTensor *self, THGenerator *_generator, double lambda)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_exponential(_generator, lambda););
}

void THTensor_(cauchy)(THTensor *self, THGenerator *_generator, double median, double sigma)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_cauchy(_generator, median, sigma););
}

void THTensor_(logNormal)(THTensor *self, THGenerator *_generator, double mean, double stdv)
{
  TH_TENSOR_APPLY(real, self, *self_data = (real)THRandom_logNormal(_generator, mean, stdv););
}


void THTensor_(multinomialAliasSetup)(THTensor *probs, THLongTensor *J, THTensor *q)
{
  long inputsize = THTensor_(nElement)(probs);
  long i = 0;
  THLongTensor *smaller = THLongTensor_newWithSize1d(inputsize);
  THLongTensor *larger = THLongTensor_newWithSize1d(inputsize);
  long small_c = 0;
  long large_c = 0;
  THLongTensor_resize1d(J, inputsize);
  THTensor_(resize1d)(q, inputsize);
  real *q_data = THTensor_(data)(q);
  long *J_data = THLongTensor_data(J);
      
  for(i = 0; i < inputsize; i++)
    {
      THTensor_fastSet1d(J, i, 0L);
      real val = THTensor_fastGet1d(probs, i);
      THTensor_fastSet1d(q, i, inputsize*val);
      
      if (inputsize * val < 1.0)
        {
          THTensor_fastSet1d(smaller, small_c, i);
          small_c += 1;
        }
      else
        {
          THTensor_fastSet1d(larger, large_c, i);
          large_c += 1;
        }
    }

  // Loop through and create little binary mixtures that
  // appropriately allocate the larger outcomes over the
  // overall uniform mixture.
  long large, small;
  while(small_c > 0 && large_c > 0)
    {
      large = THTensor_fastGet1d(larger, large_c-1);
      small = THTensor_fastGet1d(smaller, small_c-1);
      
      THTensor_fastSet1d(J, small, large);
      q_data[large * q->stride[0]] -= 1.0 - THTensor_fastGet1d(q, small);

      if(q_data[large] < 1.0)
        {
          THTensor_fastSet1d(smaller, small_c-1, large);
          large_c -= 1;
        }
      else
        {
          THTensor_fastSet1d(larger, large_c-1, large);
          small_c -= 1;
        }
    }

  real q_min = THTensor_fastGet1d(q, inputsize-1);
  real q_max = q_min;
  real q_temp;
  for(i=0; i < inputsize; i++)
    {
      q_temp = THTensor_fastGet1d(q, i);
      if(q_temp < q_min)
        q_min = q_temp;
      else if(q_temp > q_max)
        q_max = q_temp;
    }
  THArgCheckWithCleanup((q_min > 0),
                        THCleanup(THLongTensor_free(smaller); THLongTensor_free(larger);), 2,
                        "q_min is less than 0");
  
  if(q_max > 1)
    {
      for(i=0; i < inputsize; i++)
        {
          q_data[i*q->stride[0]] /= q_max;
        }
    }
  for(i=0; i<inputsize; i++)
    {
      // sometimes an large index isn't added to J. 
      // fix it by making the probability 1 so that J isn't indexed.
      if(J_data[i] <= 0)
        q_data[i] = 1.0;
    }
  THLongTensor_free(smaller);
  THLongTensor_free(larger);
}
void THTensor_(multinomialAliasDraw)(THLongTensor *self, THGenerator *_generator, THLongTensor *J, THTensor *q)
{
  long K = THLongTensor_nElement(J);
  long output_nelem = THLongTensor_nElement(self);
  
  int i = 0, _mask=0;
  real _q;
  long rand_ind, sample_idx, J_sample, kk_sample;
  for(i=0; i< output_nelem; i++)
    {
      rand_ind = (long)THRandom_uniform(_generator, 0, K) ;
      _q = THTensor_fastGet1d(q, rand_ind);

      _mask = THRandom_bernoulli(_generator, _q);
      
      J_sample = THTensor_fastGet1d(J, rand_ind);

      sample_idx = J_sample*(1 -_mask) + (rand_ind+1L) * _mask;

      THTensor_fastSet1d(self, i, sample_idx-1L);
    }
}
void THTensor_(multinomial)(THLongTensor *self, THGenerator *_generator, THTensor *prob_dist, int n_sample, int with_replacement)
{
  int start_dim = THTensor_(nDimension)(prob_dist);
  long n_dist;
  long n_categories;
  THDoubleTensor* cum_dist;
  int i,j,k;

  if (start_dim == 1)
  {
    THTensor_(resize2d)(prob_dist, 1, THTensor_(size)(prob_dist, 0));
  }

  n_dist = THTensor_(size)(prob_dist, 0);
  n_categories = THTensor_(size)(prob_dist, 1);

  THArgCheck(n_sample > 0, 2, "cannot sample n_sample < 0 samples");

  if (!with_replacement)
  {
    THArgCheck((!with_replacement) && (n_sample <= n_categories), 2, \
    "cannot sample n_sample > prob_dist:size(1) samples without replacement");
  }

  /* cumulative probability distribution vector */
  cum_dist = THDoubleTensor_newWithSize1d(n_categories);

  /* will contain multinomial samples (category indices to be returned) */
  THLongTensor_resize2d(self, n_dist , n_sample);

  for (i=0; i<n_dist; i++)
  {
    /* Get normalized cumulative distribution from prob distribution */
    double sum = 0;
    for (j=0; j<n_categories; j++)
    {
      sum += THStorage_(get)( \
        prob_dist->storage, \
        prob_dist->storageOffset+i*prob_dist->stride[0]+j*prob_dist->stride[1] \
      );
      THDoubleStorage_set(
        cum_dist->storage, \
        cum_dist->storageOffset+j*cum_dist->stride[0], \
        sum \
      );
    }
    THArgCheckWithCleanup((sum > 0), THCleanup(THDoubleTensor_free(cum_dist);), 2,
                          "invalid multinomial distribution (sum of probabilities <= 0)");
    /* normalize cumulative probability distribution so that last val is 1
    i.e. doesn't assume original prob_dist row sums to one */
    if ( (sum > 0) || ( ( sum < 1.00001) && (sum > 0.99999) ) )
    {
      for (j=0; j<n_categories; j++)
      {
        THDoubleTensor_data(cum_dist)[j*cum_dist->stride[0]] /= sum;
      }
    }

    for (j=0; j<n_sample; j++)
    {
      /* sample a probability mass from a uniform distribution */
      double uniform_sample = THRandom_uniform(_generator, 0, 1);
      /* Do a binary search for the slot in which the prob falls
      ie cum_dist[row][slot-1] < uniform_prob < cum_distr[row][slot] */
      int left_pointer = 0;
      int right_pointer = n_categories;
      int mid_pointer;
      double cum_prob;
      int sample_idx;
      /* Make sure the last cumulative distribution bucket sums to 1 */
      THDoubleTensor_data(cum_dist)[(n_categories-1)*cum_dist->stride[0]] = 1;

      while(right_pointer - left_pointer > 0)
      {
          mid_pointer = left_pointer + (right_pointer - left_pointer) / 2;
          cum_prob = THDoubleStorage_get( \
            cum_dist->storage, \
            cum_dist->storageOffset+mid_pointer*cum_dist->stride[0] \
          );
          if (cum_prob < uniform_sample)
          {
            left_pointer = mid_pointer + 1;
          }
          else
          {
            right_pointer = mid_pointer;
          }
      }
      sample_idx = left_pointer;

       /* store in result tensor (will be incremented for lua compat by wrapper) */
      THLongStorage_set( \
        self->storage, \
        self->storageOffset+i*self->stride[0]+j*self->stride[1], \
        sample_idx \
      );

      /* Once a sample is drawn, it cannot be drawn again. ie sample without replacement */
      if (!with_replacement)
      {
        /* update cumulative distribution so that sample cannot be drawn again */
        double diff;
        double new_val = 0;
        double sum;

        if (sample_idx != 0)
        {
          new_val = THDoubleStorage_get( \
            cum_dist->storage, \
            cum_dist->storageOffset+(sample_idx-1)*cum_dist->stride[0] \
          );
        }
        /* marginal cumulative mass (i.e. original probability) of sample */
        diff = THDoubleStorage_get( \
          cum_dist->storage, \
          cum_dist->storageOffset+sample_idx*cum_dist->stride[0] \
        ) - new_val;
        /* new sum of marginals is not one anymore... */
        sum = 1.0 - diff;
        for (k=0; k<n_categories; k++)
        {
          new_val = THDoubleStorage_get( \
            cum_dist->storage, \
            cum_dist->storageOffset+k*cum_dist->stride[0] \
          );
          if (k >= sample_idx)
          {
            /* remove sampled probability mass from later cumulative probabilities */
            new_val -= diff;
          }
          /* make total marginals sum to one */
          new_val /= sum;
          THDoubleStorage_set( \
            cum_dist->storage, \
            cum_dist->storageOffset+k*cum_dist->stride[0], \
            new_val \
          );
        }
      }
    }
  }

  THDoubleTensor_free(cum_dist);

  if (start_dim == 1)
  {
    THLongTensor_resize1d(self, n_sample);
    THTensor_(resize1d)(prob_dist, n_categories);
  }
}

#endif

#if defined(TH_REAL_IS_BYTE)
void THTensor_(getRNGState)(THGenerator *_generator, THTensor *self)
{
  static const size_t size = sizeof(THGenerator);
  THGenerator *rng_state;
  THTensor_(resize1d)(self, size);
  THArgCheck(THTensor_(nElement)(self) == size, 1, "RNG state is wrong size");
  THArgCheck(THTensor_(isContiguous)(self), 1, "RNG state needs to be contiguous");
  rng_state = (THGenerator *)THTensor_(data)(self);
  THGenerator_copy(rng_state, _generator);
}

void THTensor_(setRNGState)(THGenerator *_generator, THTensor *self)
{
  static const size_t size = sizeof(THGenerator);
  THGenerator *rng_state;
  THArgCheck(THTensor_(nElement)(self) == size, 1, "RNG state is wrong size");
  THArgCheck(THTensor_(isContiguous)(self), 1, "RNG state needs to be contiguous");
  rng_state = (THGenerator *)THTensor_(data)(self);
  THArgCheck(THGenerator_isValid(rng_state), 1, "Invalid RNG state");
  THGenerator_copy(_generator, rng_state);
}
#endif

#endif