std::vector<ParallelTensor*> parallel_inputs;
  std::vector<std::unique_ptr<ParallelTensor>> implicitly_broadcast_tensors;
  parallel_inputs.reserve(inputs.size());
  implicitly_broadcast_tensors.reserve(inputs.size());  // not tight
  for (const auto& input : inputs) {
    if (absl::holds_alternative<TFE_TensorHandle*>(input)) {
      if (operation_name == std::string("_EagerConst")) {

In our experience and testing, these types force us to represent data in inefficient ways because they are general purpose.
Ztunnel is not general purpose; it has an extremely tight goal.
We can exploit this to make a more efficient protocol, which is critical to achieve our resource footprint goals.

  pop_backward_tape.release()();

  std::vector<int64_t> targets;
  std::vector<Gradient*> used_in_grads;
  // We may end up with slightly fewer elements than we reserve, but grad.size()
  // should be a reasonably tight upper bound.
  targets.reserve(grad.size());
  used_in_grads.reserve(grad.size());
  std::unordered_map<int64_t, TapeTensor> sources_that_are_targets;

I say--that's the same thing, you know.'

  `Not the same thing a bit!' said the Hatter.  `You might just
as well say that "I see what I eat" is the same thing as "I eat
what I see"!'

  `You might just as well say,' added the March Hare, `that "I
like what I get" is the same thing as "I get what I like"!'

  `You might just as well say,' added the Dormouse, who seemed to

I say--that's the same thing, you know.'

  `Not the same thing a bit!' said the Hatter.  `You might just
as well say that "I see what I eat" is the same thing as "I eat
what I see"!'

  `You might just as well say,' added the March Hare, `that "I
like what I get" is the same thing as "I get what I like"!'

  `You might just as well say,' added the Dormouse, who seemed to

 * annotated with LargeTest.
 *
 * <p>Why use a custom annotation instead of {@code android.test.suitebuilder.annotation.Suppress}?
 * I'm not completely sure that this is the right choice, but it has various advantages:
 *
 * <ul>
 *   <li>An annotation named just "Suppress" might someday be treated by a non-Android tool as a
 *       suppression. This would follow the precedent of many of our annotation processors, which

<component name="ProjectRunConfigurationManager">
  <configuration default="false" name="Symbol Light Classes Tests" type="GradleRunConfiguration" factoryName="Gradle" folderName="Analysis">
    <ExternalSystemSettings>
      <option name="executionName" />
      <option name="externalProjectPath" value="$PROJECT_DIR$" />
      <option name="externalSystemIdString" value="GRADLE" />
      <option name="scriptParameters" value="" />
      <option name="taskDescriptions">

 * annotated with LargeTest.
 *
 * <p>Why use a custom annotation instead of {@code android.test.suitebuilder.annotation.Suppress}?
 * I'm not completely sure that this is the right choice, but it has various advantages:
 *
 * <ul>
 *   <li>An annotation named just "Suppress" might someday be treated by a non-Android tool as a
 *       suppression. This would follow the precedent of many of our annotation processors, which

<component name="ProjectRunConfigurationManager">
  <configuration default="false" name="Test: Commonizer / Light" type="GradleRunConfiguration" factoryName="Gradle" folderName="Tests">
    <ExternalSystemSettings>
      <option name="executionName" />
      <option name="externalProjectPath" value="$PROJECT_DIR$" />
      <option name="externalSystemIdString" value="GRADLE" />
      <option name="scriptParameters" value="" />
      <option name="taskDescriptions">

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