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/*! \file
    \brief uncompress sparse matrix from the host side 
*/
#pragma once

#include "cutlass/coord.h"
#include "cutlass/util/host_tensor.h"
#include "cutlass/tensor_view.h"
#include "cutlass/util/tensor_view_io.h"
#include "cutlass/util/reference/host/gemm.h"

namespace cutlass {

template <typename ElementA, typename LayoutA, typename ElementE,
          typename LayoutE>
void uncompress(TensorRef<ElementA, LayoutA> uncompressed_tensor_a,
                TensorRef<ElementA, LayoutA> tensor_a,
                TensorRef<ElementE, LayoutE> tensor_e, int row, int col) {
  // How many uncompressed data we can get with ElementE meta data
  int DecompressedElementsPerElementE =
      256 / cutlass::sizeof_bits<ElementA>::value;

  // Process 4bit meta data a time 
  int step;

  // 1:2 or 2:4 or 4:8
  int a, b;

  if (cutlass::sizeof_bits<ElementA>::value == 4) {
    step = 8;
    a = 4;
    b = 8;
  } else if (cutlass::sizeof_bits<ElementA>::value == 8) {
    step = 4;
    a = 2;
    b = 4;
  } else if (cutlass::sizeof_bits<ElementA>::value == 16) {
    step = 4;
    a = 2;
    b = 4;
  } else if (cutlass::sizeof_bits<ElementA>::value == 32) {
    step = 2;
    a = 1;
    b = 2;
  }

  int ElementsPerE = (cutlass::sizeof_bits<ElementA>::value == 4) ? 2 : 1;

  for (int r = 0; r < row; ++r) {
    for (int c = 0; c < (col / DecompressedElementsPerElementE); ++c) {

      ElementE meta = tensor_e.at(MatrixCoord(r, c));

      for (int i = 0; i < DecompressedElementsPerElementE; i += step) {
        int e = (meta >> (i / step * 4)) & 0xf;
        int idx0 = e & 0x3;
        int idx1 = e >> 2;

        if (a == 1) idx0 = idx0 / 2;

        for (int ii = 0; ii < step; ii += ElementsPerE) {
          int real_col =
              c * DecompressedElementsPerElementE + i + ii;
          int compressed_col = (real_col / b) * a;

          if (ii == (idx0 * ElementsPerE)) {
            uncompressed_tensor_a.at(MatrixCoord(r, real_col)) =
                tensor_a.at(MatrixCoord(r, compressed_col));
            if (ElementsPerE == 2)
              uncompressed_tensor_a.at(MatrixCoord(r, real_col + 1)) =
                  tensor_a.at(MatrixCoord(r, compressed_col + 1));
          } else if ((ii == (idx1 * ElementsPerE)) && (a != 1)) {
            uncompressed_tensor_a.at(MatrixCoord(r, real_col)) =
                tensor_a.at(MatrixCoord(r, compressed_col + ElementsPerE));
            if (ElementsPerE == 2)
              uncompressed_tensor_a.at(MatrixCoord(r, real_col + 1)) =
                  tensor_a.at(
                      MatrixCoord(r, compressed_col + ElementsPerE + 1));
          } else {
            uncompressed_tensor_a.at(MatrixCoord(r, real_col)) =
                ElementA(0);
            if (ElementsPerE == 2)
              uncompressed_tensor_a.at(MatrixCoord(r, real_col + 1)) =
                  ElementA(0);
          }
        }
      }
    }
  }
}
} // namespace cutlass

