fix the row split recovery, add per iteration random number seed

src/learner/learner-inl.hpp

@@ -34,6 +34,8 @@ class BoostLearner : public rabit::ISerializable {
     prob_buffer_row = 1.0f;
     distributed_mode = 0;
     pred_buffer_size = 0;
+    seed_per_iteration = 0;
+    seed = 0;
   }
   virtual ~BoostLearner(void) {
     if (obj_ != NULL) delete obj_;
@@ -102,7 +104,10 @@ class BoostLearner : public rabit::ISerializable {
       this->SetParam("updater", "grow_colmaker,refresh,prune");
     }
     if (!strcmp(name, "eval_metric")) evaluator_.AddEval(val);
-    if (!strcmp("seed", name)) random::Seed(atoi(val));
+    if (!strcmp("seed", name)) {
+      this->seed = seed; random::Seed(atoi(val));
+    }
+    if (!strcmp("seed_per_iter", name)) seed_per_iteration = atoi(val);
     if (!strcmp(name, "num_class")) this->SetParam("num_output_group", val);
     if (!strcmp(name, "nthread")) {
       omp_set_num_threads(atoi(val));
@@ -222,6 +227,9 @@ class BoostLearner : public rabit::ISerializable {
    * \param p_train pointer to the data matrix
    */
   inline void UpdateOneIter(int iter, const DMatrix &train) {
+    if (seed_per_iteration || rabit::IsDistributed()) {
+      random::Seed(this->seed * kRandSeedMagic);
+    }
     this->PredictRaw(train, &preds_);
     obj_->GetGradient(preds_, train.info, iter, &gpair_);
     gbm_->DoBoost(train.fmat(), this->FindBufferOffset(train), train.info.info, &gpair_);
@@ -369,6 +377,12 @@ class BoostLearner : public rabit::ISerializable {
     }
   };
   // data fields
+  // stored random seed
+  int seed;
+  // whether seed the PRNG each iteration
+  // this is important for restart from existing iterations
+  // default set to no, but will auto switch on in distributed mode
+  int seed_per_iteration;
   // silent during training
   int silent;
   // distributed learning mode, if any, 0:none, 1:col, 2:row
@@ -397,6 +411,8 @@ class BoostLearner : public rabit::ISerializable {
   std::vector<bst_gpair> gpair_;
 
  protected:
+  // magic number to transform random seed
+  const static int kRandSeedMagic = 127;
   // cache entry object that helps handle feature caching
   struct CacheEntry {
     const DMatrix *mat_;