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clarification: approximation or exact search? #27

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kmgl opened this Issue Jun 4, 2016 · 4 comments

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kmgl commented Jun 4, 2016

When looking at your description I was wondering whether this library uses kd-trees to determine exact results in the knn and radius search or if there are approximations? For me it looks that you do not perform approximations; which would make sense for low-dimensional point-clouds.

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jlblancoc Jun 4, 2016

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Hi @kmgl ,

The original FLANN library included approximated (hence the A) methods, but nanoflann does only exact searches. Let me know if there is some confusing part in the docs regarding this point...

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jlblancoc commented Jun 4, 2016

Hi @kmgl ,

The original FLANN library included approximated (hence the A) methods, but nanoflann does only exact searches. Let me know if there is some confusing part in the docs regarding this point...

@jlblancoc jlblancoc closed this Jun 4, 2016

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kmgl Jun 4, 2016

Thank you very much @jlblancoc , for the clarification.
I guess the confusing part is that the library is called nanoflann (with the A), which I understand since it is based on FLANN. In the brief description it says:

nanoflann: a C++ header-only library for Nearest Neighbor (NN) search wih KD-trees

which indicates that it is without the approximation. You referred in the description to ANN algorithms (based on the original paper) and I had a look at the original paper and the main contribution of that paper is the approximation but than again your description also says:

There is no automatic algorithm configuration (as described in the original Muja & Lowe's paper).

which further indicates that you don't perform approximation. Maybe a clarifying statement in the:
Section:

1.5. What can nanoflann do?

might be also useful for others. I just wanted to make sure that my assumption that your library provides exact queries is correct. Since I want to use it for broadphase collision avoidance. Thank you again for the clarification.

kmgl commented Jun 4, 2016

Thank you very much @jlblancoc , for the clarification.
I guess the confusing part is that the library is called nanoflann (with the A), which I understand since it is based on FLANN. In the brief description it says:

nanoflann: a C++ header-only library for Nearest Neighbor (NN) search wih KD-trees

which indicates that it is without the approximation. You referred in the description to ANN algorithms (based on the original paper) and I had a look at the original paper and the main contribution of that paper is the approximation but than again your description also says:

There is no automatic algorithm configuration (as described in the original Muja & Lowe's paper).

which further indicates that you don't perform approximation. Maybe a clarifying statement in the:
Section:

1.5. What can nanoflann do?

might be also useful for others. I just wanted to make sure that my assumption that your library provides exact queries is correct. Since I want to use it for broadphase collision avoidance. Thank you again for the clarification.

jlblancoc added a commit that referenced this issue Jun 5, 2016

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jlblancoc Jun 5, 2016

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Ok, thanks for the feedback! I've just updated the README.

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jlblancoc commented Jun 5, 2016

Ok, thanks for the feedback! I've just updated the README.

codegrafix added a commit to codegrafix/nanoflann that referenced this issue Apr 26, 2017

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codingforfun Nov 3, 2017

Hi,
I was stumbling over the exact same question. From the README I got the idea that this library most probably does exact searches, but anyway wasn't not 100% sure. So maybe you could even make a stronger statement about this in the README to make this really 100% clear. Thx.

codingforfun commented Nov 3, 2017

Hi,
I was stumbling over the exact same question. From the README I got the idea that this library most probably does exact searches, but anyway wasn't not 100% sure. So maybe you could even make a stronger statement about this in the README to make this really 100% clear. Thx.

jlblancoc added a commit that referenced this issue Nov 3, 2017

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