softmax.h

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#ifndef TVM_TOPI_CUDA_SOFTMAX_H_
#define TVM_TOPI_CUDA_SOFTMAX_H_
 
#include <tvm/target/generic_func.h>
#include <tvm/te/operation.h>
#include <tvm/te/schedule_pass.h>
#include <tvm/topi/detail/fuse.h>
#include <tvm/topi/tags.h>
 
namespace tvm {
namespace topi {
 
using namespace tvm::te;
 
namespace cuda {
 
inline Schedule schedule_softmax(const Target& target, const Array<Tensor>& outs) {
  Array<Operation> out_ops;
  for (auto t : outs) {
    out_ops.push_back(t->op);
  }
  auto s = create_schedule(out_ops);
 
  auto softmax = outs[0];
  tvm::te::Tensor max_elem;
  tvm::te::Tensor expsum;
  tvm::te::Tensor exp;
  bool has_exp = false;
 
  auto tag = softmax->op.as<ComputeOpNode>()->tag;
  if (tag == "softmax_output") {
    expsum = softmax->op->InputTensors()[1];
    exp = softmax->op->InputTensors()[0];
    max_elem = s[exp]->op->InputTensors()[1];
    has_exp = true;
  } else if (tag == "log_softmax_output") {
    max_elem = softmax->op->InputTensors()[1];
    expsum = softmax->op->InputTensors()[2];
  } else {
    LOG(ERROR) << "Tag is expected to be softmax_output or log_softmax_output. Got " << tag;
  }
 
  int num_thread = 64;
  auto block_x = tvm::te::thread_axis(Range(), "blockIdx.x");
  auto thread_x = tvm::te::thread_axis(Range(0, num_thread), "threadIdx.x");
 
  if (has_exp) {
    s[exp].bind(exp->op.as<ComputeOpNode>()->axis[0], block_x);
  }
 
  s[max_elem].bind(max_elem->op.as<ComputeOpNode>()->axis[0], block_x);
 
  auto k = expsum->op.as<ComputeOpNode>()->reduce_axis[0];
  IterVar ko, ki;
  s[expsum].split(k, num_thread, &ko, &ki);
  auto EF = s.rfactor(expsum, ki)[0];
  s[expsum].bind(s[expsum]->op.as<ComputeOpNode>()->axis[0], block_x);
  s[expsum].bind(s[expsum]->op.as<ComputeOpNode>()->reduce_axis[0], thread_x);
  s[EF].compute_at(s[expsum], s[expsum]->op.as<ComputeOpNode>()->reduce_axis[0]);
  s[expsum].set_store_predicate(thread_x->var == 0);
 
  IterVar tx, xi;
  s[softmax].split_by_nparts(softmax->op.as<ComputeOpNode>()->axis[1], num_thread, &tx, &xi);
  s[softmax].bind(tx, thread_x);
 
  return s;
}
 
}  // namespace cuda
}  // namespace topi
}  // namespace tvm
#endif  // TVM_TOPI_CUDA_SOFTMAX_H_