Update webcam-transfer-learning with tf.data.webcam API

[kangyizhang]

This change is 

[bileschi]

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webcam-transfer-learning/package.json, line 13 at r1 (raw file):

@tensorflow/tfjs-data": "link:.yalc/@tensorflow/tfjs-data",

Probably didn't mean to include this?

[bileschi]

Reviewed 4 of 4 files at r1.
Reviewable status: 0 of 1 approvals obtained (waiting on @kangyizhang)

[caisq]

Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @caisq, @dsmilkov, and @kangyizhang)

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webcam-transfer-learning/index.js, line 160 at r2 (raw file):

return (await webcam.capture())

The intermediate tensors (i.e., the one output by expanDims(0)) should be tidied. Otherwise, you'll get memory leaks.

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webcam-transfer-learning/index.js, line 163 at r2 (raw file):

tf.scalar(127)

This can be simplified to div(127). Same for the sub() call below.

[kangyizhang]

Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @bileschi, @caisq, and @dsmilkov)

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webcam-transfer-learning/index.js, line 160 at r2 (raw file):

Previously, caisq (Shanqing Cai) wrote…

return (await webcam.capture())

The intermediate tensors (i.e., the one output by expanDims(0)) should be tidied. Otherwise, you'll get memory leaks.

The returned tensor is disposed at line: https://github.com/tensorflow/tfjs-examples/pull/267/files#diff-030148133b399b3f844d841a0514bfbbR58

It seems that tf.tidy() can not be used here, because webcamIterator.capture() is async function, and async functions are not allowed in tf.tidy().

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webcam-transfer-learning/index.js, line 163 at r2 (raw file):

Previously, caisq (Shanqing Cai) wrote…

tf.scalar(127)

This can be simplified to div(127). Same for the sub() call below.

Done.

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webcam-transfer-learning/package.json, line 13 at r1 (raw file):

Previously, bileschi (Stanley Bileschi) wrote…

@tensorflow/tfjs-data": "link:.yalc/@tensorflow/tfjs-data",

Probably didn't mean to include this?

removed.

[caisq]

Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @bileschi, @caisq, @dsmilkov, and @kangyizhang)

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webcam-transfer-learning/index.js, line 160 at r2 (raw file):

Previously, kangyizhang (Kangyi Zhang) wrote…

The returned tensor is disposed at line: https://github.com/tensorflow/tfjs-examples/pull/267/files#diff-030148133b399b3f844d841a0514bfbbR58

It seems that tf.tidy() can not be used here, because webcamIterator.capture() is async function, and async functions are not allowed in tf.tidy().

I understand you dispose the tensor returned by this function. However, this function allocates other tensors that are not cleaned up, which leads to memory leak. You can do something like the following:

const img = await webcam.capture();
const processedImg = tf.tidy(() => img.expandDims(0).toFloat().div(127).sub(1));
img.dispose();
return processedImg;

[kangyizhang]

Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @bileschi, @caisq, and @dsmilkov)

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webcam-transfer-learning/index.js, line 160 at r2 (raw file):

Previously, caisq (Shanqing Cai) wrote…

I understand you dispose the tensor returned by this function. However, this function allocates other tensors that are not cleaned up, which leads to memory leak. You can do something like the following:

const img = await webcam.capture();
const processedImg = tf.tidy(() => img.expandDims(0).toFloat().div(127).sub(1));
img.dispose();
return processedImg;

Done. Sorry I lost track of this PR and thank you for explaining this to me.

[kangyizhang]

Friendly ping.

[caisq]

Reviewable status: 1 change requests, 0 of 1 approvals obtained (waiting on @bileschi, @caisq, and @dsmilkov)

[caisq]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @bileschi, @caisq, and @dsmilkov)