add simple upsampling

guide/basic.cpp

@@ -107,6 +107,21 @@ int main(void) {
     printf("\n");
   }
 
+  printf("upsampling\n");
+  TensorContainer<cpu, 2> small(Shape2(2, 2));
+  small[0][0] = 1.0f;
+  small[0][1] = 2.0f;
+  small[1][0] = 3.0f;
+  small[1][1] = 4.0f;
+  TensorContainer<cpu, 2> large(Shape2(6, 6));
+  large = upsampling(small, 3);
+  for (index_t i = 0; i < large.size(0); ++i) {
+    for (index_t j = 0; j < large.size(1); ++j) {
+      printf("%.2f ", large[i][j]);
+    }
+    printf("\n");
+  }
+
   // shutdown tensor enigne after usage
   ShutdownTensorEngine<cpu>();
   return 0;

mshadow/extension.h

@@ -28,4 +28,5 @@
 #include "./extension/slice.h"
 #include "./extension/take.h"
 #include "./extension/take_grad.h"
+#include "./extension/spatial_upsampling.h"
 #endif  // MSHADOW_EXTENSION_H_

mshadow/extension/spatial_upsampling.h

@@ -0,0 +1,71 @@
+/*!
+ * Copyright (c) 2015 by Contributors
+ * \file spatial_upsampling.h
+ * \brief
+ * \author Bing Xu
+*/
+#ifndef MSHADOW_EXTENSION_SPATIAL_UPSAMPLING_H_
+#define MSHADOW_EXTENSION_SPATIAL_UPSAMPLING_H_
+#include "../extension.h"
+
+namespace mshadow {
+namespace expr {
+
+/*! \brief nearest neighboor upsampling
+ *         out(x, y) = in(int(x / scale_x), int(y / scale_y))
+ *  \tparam SrcExp source expression
+ *  \tparam DType data type
+ *  \tparam srcdim source dimension
+ */
+template<typename SrcExp, typename DType, int srcdim>
+struct UpSamplingExp :
+  public MakeTensorExp<UpSamplingExp<SrcExp, DType, srcdim>,
+                       SrcExp, srcdim, DType> {
+  /*! \brief source oprand */
+  const SrcExp &src_;
+  /*! \brief up sampling scale */
+  index_t scale_;
+  /*! \brief constructor */
+  UpSamplingExp(const SrcExp &src, index_t scale)
+    : src_(src), scale_(scale) {
+    this->shape_ = ShapeCheck<srcdim, SrcExp>::Check(src_);
+    this->shape_[srcdim - 2] *= scale_;
+    this->shape_[srcdim - 1] *= scale_;
+  }
+};
+
+
+template<typename SrcExp, typename DType, int etype>
+inline UpSamplingExp<SrcExp, DType, ExpInfo<SrcExp>::kDim>
+upsampling(const Exp<SrcExp, DType, etype> &src, index_t scale) {
+  TypeCheckPass<ExpInfo<SrcExp>::kDim >= 2>
+    ::Error_Expression_Does_Not_Meet_Dimension_Req();
+  return UpSamplingExp<SrcExp, DType, ExpInfo<SrcExp>::kDim>(src.self(), scale);
+}
+
+template<typename SrcExp, typename DType, int srcdim>
+struct Plan<UpSamplingExp<SrcExp, DType, srcdim>, DType> {
+ public:
+  explicit Plan(const UpSamplingExp<SrcExp, DType, srcdim> &e)
+    : src_(MakePlan(e.src_)),
+      scale_(e.scale_),
+      new_height_(e.shape_[srcdim - 2]),
+      src_height_(static_cast<index_t>(e.shape_[srcdim - 2] / 2)) {}
+  MSHADOW_XINLINE DType Eval(index_t i, index_t j) const {
+    const index_t x = j;
+    const index_t y = i % new_height_;
+    const index_t c = i / new_height_;
+    const index_t h = static_cast<index_t>(y / scale_);
+    const index_t w = static_cast<index_t>(x / scale_);
+    return src_.Eval(c * src_height_ + h, w);
+  }
+
+ private:
+  Plan<SrcExp, DType> src_;
+  const index_t scale_;
+  const index_t new_height_;
+  const index_t src_height_;
+};
+}  // namespace expr
+}  // namespace mshadow
+#endif  // MSHADOW_EXTENSION_SPATIAL_UPSAMPLING_H_