Add the backward support for QR

paddle/fluid/operators/qr_op.h

@@ -19,6 +19,7 @@
 #include "paddle/fluid/framework/op_registry.h"
 #include "paddle/fluid/framework/operator.h"
 #include "paddle/fluid/operators/math/complex_functors.h"
+#include "paddle/fluid/operators/svd_helper.h"
 #include "paddle/fluid/platform/for_range.h"
 
 namespace paddle {
@@ -79,9 +80,11 @@ class QrCPUKernel : public framework::OpKernel<T> {
       q_data = q.mutable_data<math::Real<T>>(
           context.GetPlace(),
           size_t(batch_size * m * k * sizeof(math::Real<T>)));
+      memset(q_data, 0, size_t(batch_size * m * k * sizeof(math::Real<T>)));
     }
     auto* r_data = r.mutable_data<math::Real<T>>(
         context.GetPlace(), size_t(batch_size * k * n * sizeof(math::Real<T>)));
+    memset(r_data, 0, size_t(batch_size * k * n * sizeof(math::Real<T>)));
 
     // Implement QR by calling Eigen
     for (int i = 0; i < batch_size; ++i) {
@@ -126,8 +129,124 @@ template <typename DeviceContext, typename T>
 class QrGradKernel : public framework::OpKernel<T> {
  public:
   void Compute(const framework::ExecutionContext& ctx) const {
-    PADDLE_THROW(platform::errors::InvalidArgument(
-        "QR doesn't have the backward kernel now and will be supported soon."));
+    const framework::Tensor& Q = *ctx.Input<framework::Tensor>("Q");
+    const framework::Tensor& R = *ctx.Input<framework::Tensor>("R");
+    // Use a different name A instead of X
+    const framework::Tensor& A = *ctx.Input<framework::Tensor>("X");
+    const framework::Tensor& dQ =
+        *ctx.Input<framework::Tensor>(framework::GradVarName("Q"));
+    const framework::Tensor& dR =
+        *ctx.Input<framework::Tensor>(framework::GradVarName("R"));
+    // Use a different name dA instead of dX
+    framework::Tensor& dA =
+        *ctx.Output<framework::Tensor>(framework::GradVarName("X"));
+    dA.mutable_data<math::Real<T>>(ctx.GetPlace());
+    auto& dev_ctx = ctx.template device_context<DeviceContext>();
+    math::SetConstant<DeviceContext, T>()(dev_ctx, &dA, T(0));
+
+    auto dito = math::DeviceIndependenceTensorOperations<DeviceContext, T>(ctx);
+
+    std::string mode = ctx.Attr<std::string>("mode");
+    bool compute_q, reduced;
+    std::tie(compute_q, reduced) = _parse_qr_mode(mode);
+    if (!compute_q) {
+      PADDLE_THROW(platform::errors::InvalidArgument(
+          "The derivative of qr is not implemented when mode='r'."));
+    }
+
+    auto a_dims = A.dims();
+    int a_rank = a_dims.size();
+    int m = a_dims[a_rank - 2];
+    int n = a_dims[a_rank - 1];
+
+    if ((m > n) && (!reduced)) {
+      PADDLE_THROW(platform::errors::InvalidArgument(
+          "The derivative of qr is not implemented when mode='complete' and "
+          "nrows > ncols."));
+    }
+
+    // m >= n case
+    auto m_gt_n_case = [](
+        const framework::ExecutionContext& ctx,
+        math::DeviceIndependenceTensorOperations<DeviceContext, T>& dito,
+        const Tensor& dQ, const Tensor& dR, const Tensor& A, const Tensor& Q,
+        const Tensor& R) -> framework::Tensor {
+      // Hai-Jun Liao, Jin-Guo Liu, Lei Wang, Tao Xiang (2019). Differentiable
+      // Programming Tensor Networks.
+      // https://arxiv.org/abs/1903.09650 Section 3. QR factorization
+
+      // dR^H
+      framework::Tensor R_term;
+      if (ctx.HasInput(framework::GradVarName("R"))) {
+        R_term = dito.Matmul(R, dito.Transpose(dR));
+      } else {
+        R_term = dito.Fill(framework::vectorize<int>(R.dims()), 0);
+      }
+
+      // dQ^H * Q
+      framework::Tensor Q_term;
+      if (ctx.HasInput(framework::GradVarName("Q"))) {
+        Q_term = dito.Matmul(dito.Transpose(dQ), Q);
+      } else {
+        Q_term = dito.Fill(framework::vectorize<int>(R.dims()), 0);
+      }
+
+      framework::Tensor M_tmp1 = dito.Sub(R_term, Q_term);
+
+      // Compute M = (tril(M) + tril(M).mH()) * 0.5 Identity
+      framework::Tensor M_tril_0 = dito.TrilTriu(M_tmp1, 0, true);
+      framework::Tensor M_tril_1 = dito.TrilTriu(M_tmp1, -1, true);
+      framework::Tensor M = dito.Add(M_tril_0, dito.Transpose(M_tril_1));
+
+      framework::Tensor rhs_term;
+      if (ctx.HasInput(framework::GradVarName("Q"))) {
+        rhs_term = dito.Add(dQ, dito.Matmul(Q, M));
+      } else {
+        rhs_term = dito.Matmul(Q, M);
+      }
+
+      // dA * R^H = rhs_term
+      auto dA =
+          dito.TriangularSolve(dito.Transpose(dito.Conj(dito.Transpose(R))),
+                               dito.Transpose(rhs_term),
+                               /*upper=*/true,
+                               /*transpose=*/false,
+                               /*unitriangular=*/false);
+
+      return dito.Transpose(dA);
+    };
+
+    if (m >= n) {
+      auto dA_tmp = m_gt_n_case(ctx, dito, dQ, dR, A, Q, R);
+      framework::TensorCopy(dA_tmp, dA.place(), &dA);
+    } else {
+      // If m < n for input matrices A, we partition A = [X|Y] and R = [U|V]
+      // Calculate dX and dY individually and concatenate them to get dA
+      dA.mutable_data<math::Real<T>>(ctx.GetPlace());
+
+      auto Y = dito.Slice(A, {-1}, {m}, {n});
+      auto U = dito.Slice(R, {-1}, {0}, {m});
+      framework::Tensor dY, dX, dV, dR_tmp, dQ_prime;
+
+      if (ctx.HasInput(framework::GradVarName("R"))) {
+        dV = dito.Slice(dR, {-1}, {m}, {n});
+        dR_tmp = dito.Slice(dR, {-1}, {0}, {m});
+        // Y * dV^H
+        dQ_prime = dito.Matmul(Y, dito.Transpose(dV));
+      } else {
+        dV = dito.Fill(framework::vectorize<int>(Y.dims()), 0);
+        dQ_prime = dito.Fill(framework::vectorize<int>(Q.dims()), 0);
+      }
+
+      if (ctx.HasInput(framework::GradVarName("Q"))) {
+        dQ_prime = dito.Add(dQ_prime, dQ);
+      }
+      dX = m_gt_n_case(ctx, dito, dQ_prime, dR_tmp, A, Q, U);
+      dY = dito.Matmul(Q, dV);
+      // Concatenate dX and dY to get dA.
+      auto dA_tmp = dito.ConcatTwoTensors(dX, dY, -1);
+      framework::TensorCopy(dA_tmp, dA.place(), &dA);
+    }
   }
 };
 

paddle/fluid/operators/svd_helper.h

@@ -146,6 +146,93 @@ static std::vector<int> GetBroadcastShape(InTensors ins) {
   return broadcast_shape;
 }
 
+static inline framework::DDim ComputeAndCheckShapeForConcatOp(
+    const bool is_runtime, const std::vector<framework::DDim>& inputs_dims,
+    const size_t axis) {
+  const size_t n = inputs_dims.size();
+  auto out_dims = inputs_dims[0];
+  size_t in_zero_dims_size = out_dims.size();
+  for (size_t i = 1; i < n; i++) {
+    PADDLE_ENFORCE_EQ(inputs_dims[i].size(), out_dims.size(),
+                      platform::errors::InvalidArgument(
+                          "The shape of input[0] and input[%d] "
+                          "is expected to be equal."
+                          "But received input[0]'s shape = "
+                          "[%s], input[%d]'s shape = [%s].",
+                          i, inputs_dims[0], i, inputs_dims[i]));
+    for (size_t j = 0; j < in_zero_dims_size; j++) {
+      if (j == axis) {
+        if (is_runtime) {
+          out_dims[axis] += inputs_dims[i][j];
+        } else {
+          if (inputs_dims[i][j] == -1 || out_dims[j] == -1) {
+            out_dims[axis] = -1;
+          } else {
+            out_dims[axis] += inputs_dims[i][j];
+          }
+        }
+      } else {
+        bool check_shape =
+            is_runtime || (inputs_dims[0][j] > 0 && inputs_dims[i][j] > 0);
+        if (check_shape) {
+          // check all shape in run time
+          PADDLE_ENFORCE_EQ(inputs_dims[0][j], inputs_dims[i][j],
+                            platform::errors::InvalidArgument(
+                                "The %d-th dimension of input[0] and input[%d] "
+                                "is expected to be equal."
+                                "But received input[0]'s shape = "
+                                "[%s], input[%d]'s shape = [%s].",
+                                j, i, inputs_dims[0], i, inputs_dims[i]));
+        }
+        if (!is_runtime && out_dims[j] == -1 && inputs_dims[i][j] > 0) {
+          out_dims[j] = inputs_dims[i][j];
+        }
+      }
+    }
+  }
+  return out_dims;
+}
+
+static inline int64_t ComputeAxisForConcatOp(int64_t axis, int64_t rank) {
+  PADDLE_ENFORCE_EQ(
+      axis >= -rank && axis < rank, true,
+      platform::errors::InvalidArgument(
+          "The axis is expected to be in range of [%d, %d), but got %d", -rank,
+          rank, axis));
+  if (axis < 0) {
+    axis = axis + rank;
+  }
+  return axis > 0 ? axis : 0;
+}
+
+// Prepared for the broadcast operation
+static std::vector<int64_t> get_broadcast_batch_portion(
+    std::vector<int64_t> x, std::vector<int64_t> y) {
+  size_t size_x = x.size();
+  size_t size_y = y.size();
+  size_t size = std::max(size_x, size_y);
+  std::vector<int64_t> batchPortion(size);
+
+  ptrdiff_t i = (ptrdiff_t)size - 1;
+  for (; i >= 0; --i) {
+    ptrdiff_t offset = size - i - 1;
+    ptrdiff_t dim_x = size_x - offset - 1;
+    ptrdiff_t dim_y = size_y - offset - 1;
+    int64_t x_size = (dim_x >= 0) ? x[dim_x] : 1;
+    int64_t y_size = (dim_y >= 0) ? y[dim_y] : 1;
+
+    PADDLE_ENFORCE_EQ(
+        (x_size == y_size || x_size == 1 || y_size == 1), true,
+        platform::errors::PreconditionNotMet(
+            "The size of tensor x (%d) must match the size of tensor y "
+            "(%d) at non-singleton dimension %d.",
+            x_size, y_size, i));
+
+    batchPortion[i] = x_size != 1 ? x_size : y_size;
+  }
+  return batchPortion;
+}
+
 #define DITO_TRANSPOSE_RANK_CASE(N)             \
   case N: {                                     \
     math::Transpose<DeviceContext, T, N> trans; \
@@ -515,6 +602,54 @@ struct DeviceIndependenceTensorOperations {
     return CreateOpRunAndReturnTensor("tril_triu", inputs, attrs, out_shape);
   }
 
+  framework::Tensor TriangularSolve(const framework::Tensor& x,
+                                    const framework::Tensor& y, bool upper,
+                                    bool transpose, bool unitriangular) {
+    framework::AttributeMap attrs;
+    attrs["upper"] = upper;
+    attrs["transpose"] = transpose;
+    attrs["unitriangular"] = unitriangular;
+    NameInTensorMap inputs({{"X", {&x}}, {"Y", {&y}}});
+    auto x_dims = x.dims();
+    auto y_dims = y.dims();
+    auto y_dims_n = y_dims.size();
+    std::vector<int64_t> x_dims_vec =
+        paddle::framework::vectorize<int64_t>(x_dims);
+    std::vector<int64_t> y_dims_vec =
+        paddle::framework::vectorize<int64_t>(y_dims);
+    std::vector<int64_t> x_dims_vec_cut(x_dims_vec.begin(),
+                                        x_dims_vec.end() - 2);
+    std::vector<int64_t> y_dims_vec_cut(y_dims_vec.begin(),
+                                        y_dims_vec.end() - 2);
+    std::vector<int64_t> expand_batch_portion =
+        get_broadcast_batch_portion(x_dims_vec_cut, y_dims_vec_cut);
+    std::vector<int64_t> y_broadcast_dims({expand_batch_portion});
+    y_broadcast_dims.insert(y_broadcast_dims.end(), {y_dims_vec[y_dims_n - 2],
+                                                     y_dims_vec[y_dims_n - 1]});
+    std::vector<int> out_shape(y_broadcast_dims.begin(),
+                               y_broadcast_dims.end());
+    return CreateOpRunAndReturnTensor("triangular_solve", inputs, attrs,
+                                      out_shape);
+  }
+
+  framework::Tensor ConcatTwoTensors(const framework::Tensor& x,
+                                     const framework::Tensor& y, int axis) {
+    framework::AttributeMap attrs;
+    attrs["axis"] = axis;
+    std::vector<framework::DDim> inputs_dims({x.dims(), y.dims()});
+    NameInTensorMap inputs({{"X", {&x, &y}}});
+    size_t axis_ =
+        ComputeAxisForConcatOp(static_cast<int64_t>(axis),
+                               static_cast<int64_t>(inputs_dims[0].size()));
+    framework::DDim out_dims =
+        ComputeAndCheckShapeForConcatOp(true, inputs_dims, axis_);
+    if (out_dims[axis_] < 0) {
+      out_dims[axis_] = -1;
+    }
+    std::vector<int> out_shape = framework::vectorize<int>(out_dims);
+    return CreateOpRunAndReturnTensor("concat", inputs, attrs, out_shape);
+  }
+
   Tensor Conj(const Tensor& x) {
     Tensor out;
     auto* out_data = out.mutable_data<T>(x.dims(), context.GetPlace());

python/paddle/fluid/tests/unittests/CMakeLists.txt

@@ -975,6 +975,7 @@ set_tests_properties(test_lstm_cudnn_op PROPERTIES TIMEOUT 120)
 set_tests_properties(test_stack_op PROPERTIES TIMEOUT 120)
 set_tests_properties(test_bilinear_interp_v2_op PROPERTIES TIMEOUT 120)
 set_tests_properties(test_svd_op PROPERTIES TIMEOUT 80)
+set_tests_properties(test_qr_op PROPERTIES TIMEOUT 60)
 set_tests_properties(test_deformable_psroi_pooling PROPERTIES TIMEOUT 120)
 set_tests_properties(test_trilinear_interp_v2_op PROPERTIES TIMEOUT 120)
 set_tests_properties(test_imperative_static_runner_mnist PROPERTIES TIMEOUT 120)