Add NonMaxSuppressionV4.

[lina128]

Fixes #2450

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This change is 

[annxingyuan]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @annxingyuan, @lina128, and @pyu10055)

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tfjs-backend-wasm/src/kernels/NonMaxSuppression_util.ts, line 25 at r1 (raw file):

  selectedSize: number;
  pSelectedScores: number;
  pValidOutputs: number;

pNumValidOutputs?

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tfjs-backend-wasm/src/kernels/NonMaxSuppressionV4.ts, line 31 at r1 (raw file):

function setup(backend: BackendWasm): void {
  wasmFunc = backend.wasm.cwrap(
      'NonMaxSuppressionV4',

use symbol here

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tfjs-core/src/backends/non_max_suppression_impl.ts, line 55 at r1 (raw file):

      iouThreshold,
      scoreThreshold,
      0,                  /* softNmsSigma */

can we put the comments before the comma for consistency?

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tfjs-core/src/backends/non_max_suppression_impl.ts, line 153 at r1 (raw file):

  const elemsToPad = maxOutputSize - validOutputs;

  if (padToMaxOutputSize && elemsToPad > 0) {

padToMaxOutputSize != null

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tfjs-core/src/backends/non_max_suppression_impl.ts, line 166 at r1 (raw file):

  if (returnValidOutputs) {
    result['validOutputs'] = scalar(validOutputs, 'int32');

should this be numValidOutputs for consistency? also makes it clear that it's a scalar

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tfjs-core/src/ops/non_max_suppression_padded_async.ts, line 59 at r1 (raw file):

  const $maxOutputSize = params.maxOutputSize;
  const $iouThreshold = params.iouThreshold;
  const $scoreThreshold = params.scoreThreshold;

would it be easier just to destructure params and pass maxOutputSize, iouThreshold, scoreThreshold directly into nmsv4impl?

[lina128]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @annxingyuan, @lina128, and @pyu10055)

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tfjs-backend-wasm/src/kernels/NonMaxSuppressionV4.ts, line 31 at r1 (raw file):

Previously, annxingyuan (Ann Yuan) wrote…

use symbol here

Done.

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tfjs-core/src/backends/non_max_suppression_impl.ts, line 55 at r1 (raw file):

Previously, annxingyuan (Ann Yuan) wrote…

can we put the comments before the comma for consistency?

Done.

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tfjs-core/src/backends/non_max_suppression_impl.ts, line 153 at r1 (raw file):

Previously, annxingyuan (Ann Yuan) wrote…

padToMaxOutputSize != null

It's a boolean value, and we need to check truthy.

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tfjs-core/src/backends/non_max_suppression_impl.ts, line 166 at r1 (raw file):

Previously, annxingyuan (Ann Yuan) wrote…

should this be numValidOutputs for consistency? also makes it clear that it's a scalar

The api output name is validOutputs, so I change everything to that. Is there a naming convention for results that represent numbers should start with num_?

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tfjs-core/src/ops/non_max_suppression_padded_async.ts, line 59 at r1 (raw file):

Previously, annxingyuan (Ann Yuan) wrote…

would it be easier just to destructure params and pass maxOutputSize, iouThreshold, scoreThreshold directly into nmsv4impl?

That will mutate the inputs. Prefer to keep the input immutable.