Merge pull request apache#61 from tqchen/master

Add one hot encoder

guide/basic.cpp

@@ -65,7 +65,17 @@ int main(void) {
   for (index_t i = 0; i < choosed.size(0); ++i) {
     printf("%.2f ", choosed[i]);
   }
-  printf("\n ");
+  printf("\n");
+
+  rhs = one_hot_encode(index, 3);
+
+  for (index_t i = 0; i < lhs.size(0); ++i) {
+    for (index_t j = 0; j < lhs.size(1); ++j) {
+      printf("%.2f ", rhs[i][j]);
+    }
+    printf("\n");
+  }
+  printf("\n");
 
   // shutdown tensor enigne after usage
   ShutdownTensorEngine<cpu>();

mshadow/extension.h

@@ -24,4 +24,5 @@
 #include "./extension/concat.h"
 #include "./extension/implicit_gemm.h"
 #include "./extension/choose.h"
+#include "./extension/one_hot.h"
 #endif  // MSHADOW_EXTENSION_H_

mshadow/extension/choose.h

@@ -8,7 +8,6 @@
 #define MSHADOW_EXTENSION_CHOOSE_H_
 
 #include "../extension.h"
-#include "../packet-inl.h"
 
 namespace mshadow {
 namespace expr {
@@ -89,5 +88,3 @@ struct ExpInfo<MatChooseRowElementExp<SrcExp, IndexExp, DType> > {
 }  // namespace expr
 }  // namespace mshadow
 #endif  // MSHADOW_EXTENSION_CHOOSE_H_
-
-

mshadow/extension/one_hot.h

@@ -0,0 +1,87 @@
+/*!
+ *  Copyright (c) 2014 by Contributors
+ * \file one_hot.h
+ * \brief Create one-hot indicator array based on the index.
+ * \author Tianqi Chen
+ */
+#ifndef MSHADOW_EXTENSION_ONE_HOT_H_
+#define MSHADOW_EXTENSION_ONE_HOT_H_
+
+#include "../extension.h"
+
+
+namespace mshadow {
+namespace expr {
+/*!
+ * \brief Create a one-hot indicator array.
+ * \tparam IndexExp type of index expression
+ * \tparam DType the type of elements
+ */
+template<typename IndexExp, typename DType>
+struct OneHotEncodeExp:
+      public Exp<OneHotEncodeExp<IndexExp, DType>,
+                 DType, type::kChainer> {
+  /*! \brief index operand */
+  const IndexExp &index_;
+  /*! \brief number of choices we can have. */
+  index_t num_choices_;
+  /*! \brief constructor */
+  OneHotEncodeExp(const IndexExp &index, index_t num_choices)
+      : index_(index), num_choices_(num_choices) {}
+};
+
+template<typename IndexExp,
+         typename IDType, int e1>
+inline OneHotEncodeExp<IndexExp, default_real_t>
+one_hot_encode(const Exp<IndexExp, IDType, e1> &index, index_t num_choices) {
+  TypeCheckPass<ExpInfo<IndexExp>::kDim == 1>
+      ::Error_Expression_Does_Not_Meet_Dimension_Req();
+  return OneHotEncodeExp<IndexExp, default_real_t>(index.self(), num_choices);
+}
+
+//----------------------
+// Execution plan
+//----------------------
+template<typename IndexExp, typename DType>
+struct Plan<OneHotEncodeExp<IndexExp, DType>, DType> {
+ public:
+  explicit Plan(const OneHotEncodeExp<IndexExp, DType> &e)
+      : index_(MakePlan(e.index_)) {
+  }
+  MSHADOW_XINLINE DType Eval(index_t y, index_t x) const {
+    index_t idx = static_cast<index_t>(index_.Eval(0, y));
+    return static_cast<DType>(x == idx);
+  }
+
+ private:
+  expr::Plan<IndexExp, DType> index_;
+};
+
+template<typename IndexExp, typename DType>
+inline Plan<OneHotEncodeExp<IndexExp, DType>, DType>
+MakePlan(const OneHotEncodeExp<IndexExp, DType> &exp) {
+  return Plan<OneHotEncodeExp<IndexExp, DType>, DType>(exp);
+}
+
+template<int dim, typename IndexExp, typename DType>
+struct ShapeCheck<dim, OneHotEncodeExp<IndexExp, DType> > {
+  inline static Shape<dim>
+  Check(const OneHotEncodeExp<IndexExp, DType> &t) {
+    CHECK(dim == 2)
+        << "OneHotEncodeExp only support 2 dimension output";
+    Shape<1> shape = ShapeCheck<1, IndexExp>::Check(t.index_);
+    Shape<dim> ret;
+    ret[0] = shape[0];
+    ret[1] = t.num_choices_;
+    return ret;
+  }
+};
+
+template<typename IndexExp, typename DType>
+struct ExpInfo<OneHotEncodeExp<IndexExp, DType> > {
+  static const int kDim = 2;
+  static const int kDevMask = ExpInfo<IndexExp>::kDevMask;
+};
+}  // namespace expr
+}  // namespace mshadow
+#endif  // MSHADOW_EXTENSION_ONE_HOT_H_