eric-haibin-lin commented on a change in pull request #14683: Adding loss 
operator of a Hawkes self-exciting process
URL: https://github.com/apache/incubator-mxnet/pull/14683#discussion_r283107786
 
 

 ##########
 File path: src/operator/contrib/hawkes_ll-inl.h
 ##########
 @@ -0,0 +1,493 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/*!
+ * Copyright (c) 2018 by Contributors
+ * \file hawkes_ll-inl.h
+ * \brief Log likelihood of a marked self-exciting Hawkes process
+ * \author Caner Turkmen <[email protected]>
+ */
+#ifndef MXNET_OPERATOR_CONTRIB_HAWKES_LL_INL_H_
+#define MXNET_OPERATOR_CONTRIB_HAWKES_LL_INL_H_
+
+#include <mxnet/operator.h>
+#include <vector>
+
+#include "../operator_common.h"
+#include "../mshadow_op.h"
+#include "../mxnet_op.h"
+
+namespace mxnet {
+namespace op {
+
+namespace hawkesll {
+  enum HawkesLLOpInputs {kMu, kAlpha, kBeta, kState, kIATimes, kMarks,
+                         kValidLength, kMaxTime};
+  enum HawkesLLGradInputs {kOutGradLL, kOutGradStates, kGradMu, kGradAlpha,
+                           kGradBeta, kGradState, kGradIATimes, kGradMarks,
+                           kGradValidLength, kGradMaxTime};
+  enum HawkesLLOpOutputs {kOutLL, kOutStates};
+  enum HawkesLLOpResource {kTempSpace};
+}  // namespace hawkesll
+
+inline bool HawkesLLOpType(const nnvm::NodeAttrs& attrs,
+                            std::vector<int>* in_attrs,
+                            std::vector<int>* out_attrs) {
+  // check dimensions of the type vectors
+  CHECK_EQ(in_attrs->size(), 8U);
+  CHECK_EQ(out_attrs->size(), 2U);
+
+  TYPE_ASSIGN_CHECK(*out_attrs, hawkesll::kOutLL, in_attrs->at(0))
+  TYPE_ASSIGN_CHECK(*out_attrs, hawkesll::kOutStates, in_attrs->at(0))
+
+  for (index_t j = 0; j < 8; ++j) {
+    if (j != hawkesll::kMarks) {
+      TYPE_ASSIGN_CHECK(*in_attrs, j, out_attrs->at(0))
+    }
+  }
+  TYPE_ASSIGN_CHECK(*in_attrs, hawkesll::kMarks, 4)  // int32
+
+  return out_attrs->at(hawkesll::kOutLL) != -1;
+}
+
+inline bool HawkesLLOpShape(const nnvm::NodeAttrs& attrs,
+                             std::vector<TShape>* in_attrs,
+                             std::vector<TShape>* out_attrs) {
+  using namespace mshadow;
+  int N, T, K;
+
+  CHECK_EQ(in_attrs->size(), 8U);
+  CHECK_EQ(out_attrs->size(), 2U);
+
+  // check ndims
+  CHECK_EQ(in_attrs->at(hawkesll::kMu).ndim(), 2);  // mu (N, K)
+  CHECK_EQ(in_attrs->at(hawkesll::kAlpha).ndim(), 1);  // branching ratio (K,)
+  CHECK_EQ(in_attrs->at(hawkesll::kBeta).ndim(), 1);  // decay exponent (K,)
+  CHECK_EQ(in_attrs->at(hawkesll::kState).ndim(), 2);  // Hawkes states (N, K)
+  CHECK_EQ(in_attrs->at(hawkesll::kIATimes).ndim(), 2);  // i.a. times  (N, T)
+  CHECK_EQ(in_attrs->at(hawkesll::kMarks).ndim(), 2);  // marks (N, T)
+  CHECK_EQ(in_attrs->at(hawkesll::kValidLength).ndim(), 1);  // valid len (N,)
+  CHECK_EQ(in_attrs->at(hawkesll::kMaxTime).ndim(), 1);  // max_time (N,)
+
+  N = in_attrs->at(hawkesll::kIATimes)[0];  // number of samples in batch
+  T = in_attrs->at(hawkesll::kIATimes)[1];  // time length
+  K = in_attrs->at(hawkesll::kMu)[1];  // number of marks
+
+  // check inputs consistent
+  CHECK_EQ(in_attrs->at(hawkesll::kMu)[0], N);
+  CHECK_EQ(in_attrs->at(hawkesll::kMu)[1], K);
+  CHECK_EQ(in_attrs->at(hawkesll::kAlpha)[0], K);
+  CHECK_EQ(in_attrs->at(hawkesll::kBeta)[0], K);
+  CHECK_EQ(in_attrs->at(hawkesll::kState)[0], N);
+  CHECK_EQ(in_attrs->at(hawkesll::kState)[1], K);
+  CHECK_EQ(in_attrs->at(hawkesll::kMarks)[0], N);
+  CHECK_EQ(in_attrs->at(hawkesll::kMarks)[1], T);
+  CHECK_EQ(in_attrs->at(hawkesll::kValidLength)[0], N);
+  CHECK_EQ(in_attrs->at(hawkesll::kMaxTime)[0], N);
+
+  // infer output type
+  SHAPE_ASSIGN_CHECK(*out_attrs, hawkesll::kOutLL, Shape1(N))
+  SHAPE_ASSIGN_CHECK(*out_attrs, hawkesll::kOutStates, Shape2(N, K))
+
+  return out_attrs->at(hawkesll::kOutLL).ndim() != 0U &&
+    out_attrs->at(hawkesll::kOutStates).Size() != 0U;
+}
+
+template<int req>
+struct hawkesll_forward {
+  template<typename DType>
+  MSHADOW_XINLINE static void Map(int i,
+                                  DType* out_loglike,
+                                  DType* out_state,
+                                  const DType* mu,
+                                  const DType* alpha,
+                                  const DType* beta,
+                                  DType* state,
+                                  const DType* lags,
+                                  const int32_t* marks,
+                                  DType* valid_length,
+                                  DType* max_time,
+                                  int K,
+                                  int T,
+                                  DType* temp_register
+                                  ) {
+    int32_t ci;  // current mark
+    DType ll = 0;  // log likelihood
+    DType t = 0;  // current time
+    DType d, lda, comp;  //
+    DType *last_ = &temp_register[i * K];
+    const DType *lag_ = &lags[i * T];
+    const int32_t *mark_ = &marks[i * T];
+    DType *state_ = &out_state[i * K];
+
+    // iterate over points in sequence
+    for (index_t j = 0; j < valid_length[i]; ++j) {
+      ci = mark_[j];
+      t += lag_[j];
+      d = t - last_[ci];
+
+      lda = mu[i*K + ci] +
+            alpha[ci] * beta[ci] * state_[ci] * expf(-beta[ci] * d);
+      comp = mu[i*K + ci] * d +
+             alpha[ci] * state_[ci] * (1 - expf(-beta[ci] * d));
+
+      ll += logf(lda) - comp;
+
+      KERNEL_ASSIGN(state_[ci],
+                    req,
+                    1 + (state_[ci] * expf(-beta[ci] * d))
+                    )
+
+      last_[ci] = t;
+    }
+
+    KERNEL_ASSIGN(out_loglike[i], req, ll)
+  }
+};
+
+template<int req>
+struct hawkesll_forward_compensator {
+  template<typename DType>
+  MSHADOW_XINLINE static void Map(int i,
+                                  DType* rem_comp,
+                                  DType* out_state,
+                                  const DType* mu,
+                                  const DType* alpha,
+                                  const DType* beta,
+                                  const DType* max_time,
+                                  const int K,
+                                  const DType* last_buffer
+                                  ) {
+    DType d;
+    int m = i % K;  // mark
+    int j = i / K;  // particle
+
+    // take care of the remaining compensators and state update
+    d = max_time[j] - last_buffer[i];
+
+    // return the remaining compensator
+    KERNEL_ASSIGN(rem_comp[i], req,
+                  mu[i] * d +
+                  alpha[m] * out_state[i] * (1 - expf(-beta[m] * d)))
+
+    // update the state
+    KERNEL_ASSIGN(out_state[i], req, expf(-beta[m] * d) * out_state[i])
+  }
+};
+
+template<typename xpu>
+void HawkesLLForward(const nnvm::NodeAttrs& attrs,
+                      const OpContext& ctx,
+                      const std::vector<TBlob>& inputs,
+                      const std::vector<OpReqType>& req,
+                      const std::vector<TBlob>& outputs) {
+  using namespace mshadow;
+  using namespace mxnet_op;
+
+  Stream<xpu> *s = ctx.get_stream<xpu>();
+
+  CHECK_EQ(inputs.size(), 8U);
+  CHECK_EQ(outputs.size(), 2U);
+
+  const TBlob& out_loglike = outputs[hawkesll::kOutLL];
+  const TBlob& out_state = outputs[hawkesll::kOutStates];
+
+  int K = inputs[hawkesll::kMu].shape_[1];
+  int N = inputs[hawkesll::kIATimes].shape_[0];
+  int T = inputs[hawkesll::kIATimes].shape_[1];
+
+  MSHADOW_TYPE_SWITCH(out_loglike.type_flag_, DType, {
+    Tensor<xpu, 2, DType> temp_space = ctx.requested[hawkesll::kTempSpace]
+                                          .get_space_typed<xpu, 2, DType>(
+                                            Shape2(2*N, K),
+                                            s);
+
+    Tensor<xpu, 2, DType> last_buffer =
+        Tensor<xpu, 2, DType>(&temp_space.dptr_[0], Shape2(N, K), s);
+    Tensor<xpu, 2, DType> rem_comp =
+        Tensor<xpu, 2, DType>(&temp_space.dptr_[N*K], Shape2(N, K), s);
+
+    Tensor<xpu, 1, DType> out_loglike_ts =
+        out_loglike.get_with_shape<xpu, 1, DType>(Shape1(N), s);
+
+    last_buffer = DType(0.0);
+    rem_comp = DType(0.0);
+
+    Tensor<xpu, 2, DType> out_state_ts =
+        out_state.get_with_shape<xpu, 2, DType>(Shape2(N, K), s);
+    Tensor<xpu, 2, DType> in_state_ts =
+        inputs[hawkesll::kState].get_with_shape<xpu, 2, DType>(Shape2(N, K), 
s);
+
+    mshadow::Copy(out_state_ts, in_state_ts, s);
+
+    MXNET_ASSIGN_REQ_SWITCH(req[0], req_type, {
+      Kernel<hawkesll_forward<req_type>, xpu>::Launch(
+        s, N,
+        out_loglike.dptr<DType>(),
+        out_state.dptr<DType>(),
+        inputs[hawkesll::kMu].dptr<DType>(),  // mu
+        inputs[hawkesll::kAlpha].dptr<DType>(),  // alpha
+        inputs[hawkesll::kBeta].dptr<DType>(),  // beta
+        inputs[hawkesll::kState].dptr<DType>(),  // states
+        inputs[hawkesll::kIATimes].dptr<DType>(),  // interarrival times
+        inputs[hawkesll::kMarks].dptr<int32_t>(),  // marks
+        inputs[hawkesll::kValidLength].dptr<DType>(),  // valid_length
+        inputs[hawkesll::kMaxTime].dptr<DType>(),  // max_time
+        K,
+        T,
+        last_buffer.dptr_);
+    });
+
+    // in parallel, we take care of the remaining compensators
+    MXNET_ASSIGN_REQ_SWITCH(req[0], req_type, {
+      Kernel<hawkesll_forward_compensator<req_type>, xpu>::Launch(
+        s, N * K,
+        rem_comp.dptr_,
+        out_state.dptr<DType>(),
+        inputs[hawkesll::kMu].dptr<DType>(),  // mu
+        inputs[hawkesll::kAlpha].dptr<DType>(),  // alpha
+        inputs[hawkesll::kBeta].dptr<DType>(),  // beta
+        inputs[hawkesll::kMaxTime].dptr<DType>(),  // max_time
+        K,
+        last_buffer.dptr_);
+    });
+    out_loglike_ts -= mshadow::expr::sumall_except_dim<0>(rem_comp);
+  })
+}
+
+template<int req>
+struct hawkesll_backward {
+  template<typename DType>
+  MSHADOW_XINLINE static void Map(int i,  // indexes the sample (particle)
+                                  DType* mu_gbfr,
+                                  DType* alpha_gbfr,
+                                  DType* beta_gbfr,  // (N, K)
+                                  const DType* mu,   // (N, K)
+                                  const DType* alpha,   // (K,)
+                                  const DType* beta,    // (K,)
+                                  const DType* lags,    // (N, T)
+                                  const int32_t* marks,  // (N, T)
+                                  const DType* valid_length,  // (N,)
+                                  const DType* max_time,  // (N,)
+                                  const int K,
+                                  const int T,
+                                  DType* last_buffer,
+                                  DType* phi_buffer,
+                                  DType* phig_buffer
+                                  ) {
+    int32_t ci;
+    DType t = 0, d, lda, ed;
+    DType* last_ = &last_buffer[i * K];
+    DType* state_ = &phi_buffer[i * K];
+    DType* dstate_ = &phig_buffer[i * K];
+
+    DType* mug_ = &mu_gbfr[i * K];
+    DType* alphag_ = &alpha_gbfr[i * K];
+    DType* betag_ = &beta_gbfr[i * K];
+
+    const DType* lag_ = &lags[i * T];
+    const int32_t* mark_ = &marks[i * T];
+
+    // iterate over points
+    for (index_t j = 0; j < valid_length[i]; ++j){
+      ci = mark_[j];
+      t += lag_[j];
+      d = t - last_[ci];
+      ed = expf(-beta[ci] * d);
+
+      lda = mu[i*K + ci] + alpha[ci] * beta[ci] * state_[ci] * ed;
+
+      KERNEL_ASSIGN(mug_[ci], req, mug_[ci] + (1 / lda) - d)
+      KERNEL_ASSIGN(alphag_[ci], req,
+                    (
+                      alphag_[ci]
+                      + (beta[ci] * state_[ci] * ed) / lda
+                      - state_[ci] * (1 - ed)
+                    )
+      )
+      KERNEL_ASSIGN(betag_[ci], req,
+                    betag_[ci]
+                    + alpha[ci] * ed
+                    * (state_[ci] * (1 - beta[ci] * d) + beta[ci] * 
dstate_[ci])
+                    / lda
+                    - alpha[ci]
+                    * (dstate_[ci] * (1 - ed) + state_[ci] * d * ed)
+      )
+
+      KERNEL_ASSIGN(dstate_[ci], req, ed * (-d * state_[ci] + dstate_[ci]))
+      KERNEL_ASSIGN(state_[ci], req, 1 + (state_[ci] * ed))
+
+      last_[ci] = t;
+    }
+  }
+};
+
+
+template<int req>
+struct hawkesll_backward_compensator {
+  template<typename DType>
+  MSHADOW_XINLINE static void Map(int i,
+                                  DType* mu_gbfr,
+                                  DType* alpha_gbfr,
+                                  DType* beta_gbfr,  // (N, K)
+                                  DType* out_grad,  // read this  (N,)
+                                  const DType* mu,  // (N, K)
+                                  const DType* alpha,   // (K,)
+                                  const DType* beta,    // (K,)
+                                  const DType* max_time,  // (N,)
+                                  const int K,
+                                  DType* last_buffer,
+                                  DType* phi_buffer,
+                                  DType* phig_buffer
+                                  ) {
+    DType d;
+    int m = i % K;  // mark
+    int j = i / K;  // particle
+    DType* mug_ = &mu_gbfr[j * K];
+    DType* alphag_ = &alpha_gbfr[j * K];
+    DType* betag_ = &beta_gbfr[j * K];
+
+    // take care of the remaining compensators and state update
+    d = max_time[j] - last_buffer[i];
+
+    // take care of the gradients of the remaining compensator
+    KERNEL_ASSIGN(mug_[m], req, mug_[m] - d)
+    KERNEL_ASSIGN(alphag_[m], req,
+                  alphag_[m] - phi_buffer[i] * (1 - expf(-beta[m] * d))
+    )
+    KERNEL_ASSIGN(betag_[m], req,
+                  betag_[m] - alpha[m] * (
+                    phig_buffer[i] * (1 - expf(-beta[m] * d))
+                    + phi_buffer[i] * d * expf(-beta[m] * d)
+                  )
+    )
+
+    // // correct the gradients with respect to output gradients
+    KERNEL_ASSIGN(mug_[m], req, out_grad[j] * mug_[m])
+    KERNEL_ASSIGN(alphag_[m], req, out_grad[j] * alphag_[m])
+    KERNEL_ASSIGN(betag_[m], req, out_grad[j] * betag_[m])
+  }
+};
+
+template<typename xpu>
+void HawkesLLBackward(const nnvm::NodeAttrs& attrs,
+                         const OpContext& ctx,
+                         const std::vector<TBlob>& inputs,
+                         const std::vector<OpReqType>& req,
+                         const std::vector<TBlob>& outputs) {
+  CHECK_EQ(inputs.size(), 10U);
+  CHECK_EQ(outputs.size(), 8U);
+  CHECK_EQ(req.size(), 8U);
+
+  mshadow::Stream<xpu> *s = ctx.get_stream<xpu>();
+
+  int K = inputs[hawkesll::kGradMu].shape_[1];  // mu data
+  int N = inputs[hawkesll::kGradIATimes].shape_[0];
+  int T = inputs[hawkesll::kGradIATimes].shape_[1];
+
+  CHECK_EQ(inputs[hawkesll::kOutGradLL].shape_[0], N);  // grad of out 0 (LL)
+  CHECK_EQ(inputs[hawkesll::kOutGradStates].shape_[0], N);  // grad out 
1-states
+  CHECK_EQ(inputs[hawkesll::kOutGradStates].shape_[1], K);
+
+  const TBlob& out_grad = inputs[hawkesll::kOutGradLL];
+
+  using namespace mshadow;
+  using namespace mxnet_op;
+  MSHADOW_TYPE_SWITCH(out_grad.type_flag_, DType, {
+    // allocate gradient buffers
+    Tensor<xpu, 2, DType> bfr =
+        ctx.requested[hawkesll::kTempSpace]
+           .get_space_typed<xpu, 2, DType>(Shape2(6*N, K), s);
+
+    Tensor<xpu, 2, DType> alpha_gbfr =
+        Tensor<xpu, 2, DType>(&bfr.dptr_[N*K], Shape2(N, K), s);
+    Tensor<xpu, 2, DType> beta_gbfr =
+        Tensor<xpu, 2, DType>(&bfr.dptr_[2*N*K], Shape2(N, K), s);
+    Tensor<xpu, 2, DType> last_buffer =
+        Tensor<xpu, 2, DType>(&bfr.dptr_[3*N*K], Shape2(N, K), s);
+    Tensor<xpu, 2, DType> phig_buffer =
+        Tensor<xpu, 2, DType>(&bfr.dptr_[4*N*K], Shape2(N, K), s);
+    Tensor<xpu, 2, DType> phi_buffer =
+        Tensor<xpu, 2, DType>(&bfr.dptr_[5*N*K], Shape2(N, K), s);
+
+    alpha_gbfr = DType(0.0);
+    beta_gbfr = DType(0.0);
+    last_buffer = DType(0.0);
+    phig_buffer = DType(0.0);
+
+    mshadow::Copy(phi_buffer,
+                  inputs[hawkesll::kGradState]
+                    .get_with_shape<xpu, 2, DType>(Shape2(N, K), s),
+                  s);
+
+    // get the gradient to be output
+    Tensor<xpu, 2, DType> in_grad_mu =
+        outputs[hawkesll::kMu].get_with_shape<xpu, 2, DType>(Shape2(N, K), s);
+    Tensor<xpu, 1, DType> in_grad_alpha =
+        outputs[hawkesll::kAlpha].get_with_shape<xpu, 1, DType>(Shape1(K), s);
+    Tensor<xpu, 1, DType> in_grad_beta =
+        outputs[hawkesll::kBeta].get_with_shape<xpu, 1, DType>(Shape1(K), s);
+
+    in_grad_mu = DType(0.0);
+
+    MXNET_ASSIGN_REQ_SWITCH(req[0], req_type, {
 
 Review comment:
   `req` is a list of grad_reqs that indicates whether it is required to 
compute the gradient r.s.t. input[0], input[1], ... input[7] in the forward 
function. Is it possible that they have different values (req[0] = 'write', 
req[1] = 'add_to', req[2] = 'null'). 
   
   Specifically, `MXNET_ASSIGN_REQ_SWITCH ` returns immediately if req = 
'null': 
https://github.com/apache/incubator-mxnet/blob/2fd4720342f87be80f280176ffbecb8f37e49b73/src/operator/mxnet_op.h#L92
 
   
   It looks like the kernel assume the same value for all reqs. If so, can you 
add a CHECK_EQ statement for all these reqs? Thanks.

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