# Boolean values **URL:** \ **Category:** Hdf-forum archives\ **Created:** [February 10, 2016, 9:12pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683 "2016-02-10T21:12:17Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![David1](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/73ab20/32.png) [@David1](https://forum.hdfgroup.org/u/David1)\ **Post date:** [February 10, 2016, 9:12pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/1 "2016-02-10T21:12:17Z")
Is there a way to read/write compact boolean or bitfield values? I see the bitfield types but I can't understand how it's different than writing ints. The API examples show hand packing/unpacking of the bits. How is H5T\_NATIVE\_B8 different from H5T\_NATIVE\_UINT8? Ideally I'd like 8-bit bools in memory packed into 1-bit bools on disk so it's easy to work with when loaded but stored compactly. Thanks, David ---
**Author:** ![Scott\_Mitchell](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/s/ba9def/32.png) [@Scott\_Mitchell](https://forum.hdfgroup.org/u/Scott_Mitchell)\ **Post date:** [February 10, 2016, 9:22pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/2 "2016-02-10T21:22:45Z")
I don’t think the hdf Boolean is any different than an integer. If you create a Boolean dataset and query the type, it comes back that it’s an int. You can’t tell after the fact that the data was specified as Boolean. I suppose you can create a packed Boolean type, but you’ll have to do the grunt work of muxing and de-muxing the Booleans. Ultimately, I stuck my bools in separate sbytes. > **···** > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)] On Behalf Of David > Sent: Wednesday, February 10, 2016 4:12 PM > To: HDF Users Discussion List > Subject: [Hdf-forum] Boolean values > > Is there a way to read/write compact boolean or bitfield values? I see the bitfield types but I can't understand how it's different than writing ints. The API examples show hand packing/unpacking of the bits. How is H5T\_NATIVE\_B8 different from H5T\_NATIVE\_UINT8? > Ideally I'd like 8-bit bools in memory packed into 1-bit bools on disk so it's easy to work with when loaded but stored compactly. > > Thanks, > David ---
**Author:** ![Dan](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/eada6e/32.png) [@Dan](https://forum.hdfgroup.org/u/Dan)\ **Post date:** [February 11, 2016, 9:29am UTC](https://forum.hdfgroup.org/t/boolean-values/3683/3 "2016-02-11T09:29:59Z")
You could try making your dataset using an N-bit type based on a copy of an 8-bit type, and then using the N-bit filter. You can then end up handling each Boolean value as a byte in memory, but they’re stored more compactly on disk. Might even compress well too. Dan > **···** > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)] On Behalf Of [SMITCH12@harris.com](mailto:SMITCH12@harris.com) > Sent: 10 February 2016 21:23 > To: HDF Users Discussion List > Subject: Re: [Hdf-forum] Boolean values > > I don’t think the hdf Boolean is any different than an integer. If you create a Boolean dataset and query the type, it comes back that it’s an int. You can’t tell after the fact that the data was specified as Boolean. > > I suppose you can create a packed Boolean type, but you’ll have to do the grunt work of muxing and de-muxing the Booleans. > > Ultimately, I stuck my bools in separate sbytes. > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)] On Behalf Of David > Sent: Wednesday, February 10, 2016 4:12 PM > To: HDF Users Discussion List > Subject: [Hdf-forum] Boolean values > > Is there a way to read/write compact boolean or bitfield values? I see the bitfield types but I can't understand how it's different than writing ints. The API examples show hand packing/unpacking of the bits. How is H5T\_NATIVE\_B8 different from H5T\_NATIVE\_UINT8? > Ideally I'd like 8-bit bools in memory packed into 1-bit bools on disk so it's easy to work with when loaded but stored compactly. > > Thanks, > David ---
**Author:** ![David1](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/73ab20/32.png) [@David1](https://forum.hdfgroup.org/u/David1)\ **Post date:** [February 11, 2016, 4:09pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/4 "2016-02-11T16:09:52Z")
Daniel: What are the N-bit type and filter and types you are referring to? Do you mean something I would write or are you talking about something in HDF5? Also can anyone explain how H5T\_NATIVE\_B8 is different from H5T\_NATIVE\_UINT8. > **···** > > On Thu, Feb 11, 2016 at 1:29 AM, Daniel Tetlow \ wrote: > > > You could try making your dataset using an N-bit type based on a copy of > > an 8-bit type, and then using the N-bit filter. You can then end up > > handling each Boolean value as a byte in memory, but they’re stored more > > compactly on disk. Might even compress well too. > > > > Dan > > > > \*From:\* Hdf-forum [mailto:hdf-forum-bounces@lists.hdfgroup.org] \*On > > Behalf Of \*SMITCH12@harris.com > > \*Sent:\* 10 February 2016 21:23 > > \*To:\* HDF Users Discussion List > > \*Subject:\* Re: [Hdf-forum] Boolean values > > > > I don’t think the hdf Boolean is any different than an integer. If you > > create a Boolean dataset and query the type, it comes back that it’s an > > int. You can’t tell after the fact that the data was specified as Boolean. > > > > I suppose you can create a packed Boolean type, but you’ll have to do the > > grunt work of muxing and de-muxing the Booleans. > > > > Ultimately, I stuck my bools in separate sbytes. > > > > \*From:\* Hdf-forum [mailto:hdf-forum-bounces@lists.hdfgroup.org > > \] \*On Behalf Of \*David > > \*Sent:\* Wednesday, February 10, 2016 4:12 PM > > \*To:\* HDF Users Discussion List > > \*Subject:\* [Hdf-forum] Boolean values > > > > Is there a way to read/write compact boolean or bitfield values? I see the > > bitfield types but I can't understand how it's different than writing ints. > > The API examples show hand packing/unpacking of the bits. How is > > H5T\_NATIVE\_B8 different from H5T\_NATIVE\_UINT8? > > > > Ideally I'd like 8-bit bools in memory packed into 1-bit bools on disk so > > it's easy to work with when loaded but stored compactly. > > > > Thanks, > > > > David > > > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > > Hdf-forum is for HDF software users discussion. > > Hdf-forum@lists.hdfgroup.org > > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > > Twitter: [x.com](https://twitter.com/hdf5) ---
**Author:** ![Dan](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/eada6e/32.png) [@Dan](https://forum.hdfgroup.org/u/Dan)\ **Post date:** [February 11, 2016, 4:35pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/5 "2016-02-11T16:35:26Z")
Hi, I was referring to features in HDF5. Looks like these pages in their docs might help: [https://www.hdfgroup.org/HDF5/doc/RM/RM\_H5P.html#Property-SetNbit](https://www.hdfgroup.org/HDF5/doc/RM/RM_H5P.html#Property-SetNbit) [https://www.hdfgroup.org/HDF5/doc/UG/HDF5\_Users\_Guide-Responsive%20HTML5/#t=HDF5\_Users\_Guide%2FDatasets%2FHDF5\_Datasets.htm%23TOC\_5\_6\_1\_Using\_the\_N\_bitbc-21&rhtocid=5.4.0\_1](https://www.hdfgroup.org/HDF5/doc/UG/HDF5_Users_Guide-Responsive%20HTML5/#t=HDF5_Users_Guide%2FDatasets%2FHDF5_Datasets.htm%23TOC_5_6_1_Using_the_N_bitbc-21&rhtocid=5.4.0_1) > **···** > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)] On Behalf Of David > Sent: 11 February 2016 16:10 > To: HDF Users Discussion List > Subject: Re: [Hdf-forum] Boolean values > > Daniel: What are the N-bit type and filter and types you are referring to? Do you mean something I would write or are you talking about something in HDF5? > Also can anyone explain how H5T\_NATIVE\_B8 is different from H5T\_NATIVE\_UINT8. > > On Thu, Feb 11, 2016 at 1:29 AM, Daniel Tetlow \<[daniel.tetlow@optasense.com](mailto:daniel.tetlow@optasense.com)\<[mailto:daniel.tetlow@optasense.com](mailto:daniel.tetlow@optasense.com)\>\> wrote: > You could try making your dataset using an N-bit type based on a copy of an 8-bit type, and then using the N-bit filter. You can then end up handling each Boolean value as a byte in memory, but they’re stored more compactly on disk. Might even compress well too. > > Dan > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)\<[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)\>] On Behalf Of [SMITCH12@harris.com](mailto:SMITCH12@harris.com)\<[mailto:SMITCH12@harris.com](mailto:SMITCH12@harris.com)\> > Sent: 10 February 2016 21:23 > To: HDF Users Discussion List > Subject: Re: [Hdf-forum] Boolean values > > I don’t think the hdf Boolean is any different than an integer. If you create a Boolean dataset and query the type, it comes back that it’s an int. You can’t tell after the fact that the data was specified as Boolean. > > I suppose you can create a packed Boolean type, but you’ll have to do the grunt work of muxing and de-muxing the Booleans. > > Ultimately, I stuck my bools in separate sbytes. > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)] On Behalf Of David > Sent: Wednesday, February 10, 2016 4:12 PM > To: HDF Users Discussion List > Subject: [Hdf-forum] Boolean values > > Is there a way to read/write compact boolean or bitfield values? I see the bitfield types but I can't understand how it's different than writing ints. The API examples show hand packing/unpacking of the bits. How is H5T\_NATIVE\_B8 different from H5T\_NATIVE\_UINT8? > Ideally I'd like 8-bit bools in memory packed into 1-bit bools on disk so it's easy to work with when loaded but stored compactly. > > Thanks, > David > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > Hdf-forum is for HDF software users discussion. > [Hdf-forum@lists.hdfgroup.org](mailto:Hdf-forum@lists.hdfgroup.org)\<[mailto:Hdf-forum@lists.hdfgroup.org](mailto:Hdf-forum@lists.hdfgroup.org)\> > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > Twitter: [https://twitter.com/hdf5](https://twitter.com/hdf5) ---
**Author:** ![David1](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/73ab20/32.png) [@David1](https://forum.hdfgroup.org/u/David1)\ **Post date:** [February 11, 2016, 4:39pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/6 "2016-02-11T16:39:28Z")
That looks perfect. Thank you so much. Do you know what is the purpose of the H5T\_NATIVE\_Bxx types? ---
**Author:** ![David1](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/73ab20/32.png) [@David1](https://forum.hdfgroup.org/u/David1)\ **Post date:** [February 13, 2016, 10:35pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/7 "2016-02-13T22:35:55Z")
Daniel. It looks like HDF5 data types are all sized in bytes. So while you can define a 1 bit type it is always stored as a byte. I guess I need to make my own packer. I will however use the N-bit stuff for another issue I have which is 24-bit data. Much more straight forward. David > **···** > > On Thu, Feb 11, 2016 at 8:39 AM, David \ wrote: > > > That looks perfect. Thank you so much. Do you know what is the purpose of > > the H5T\_NATIVE\_Bxx types? ---
**Author:** ![epourmal](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/e/c67d28/32.png) [@epourmal](https://forum.hdfgroup.org/u/epourmal)\ **Post date:** [February 17, 2016, 6:43pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/8 "2016-02-17T18:43:56Z")
David, > That looks perfect. Thank you so much. Do you know what is the purpose of the H5T\_NATIVE\_Bxx types? Good question 🙂 B stands for bitfield. See [https://www.hdfgroup.org/HDF5/doc1.6/Datatypes.htm](https://www.hdfgroup.org/HDF5/doc1.6/Datatypes.htm), Section 6 and current [https://www.hdfgroup.org/HDF5/doc/RM/PredefDTypes.html](https://www.hdfgroup.org/HDF5/doc/RM/PredefDTypes.html) Elena > **···** > > On Feb 11, 2016, at 10:39 AM, David \ wrote: > > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > > Hdf-forum is for HDF software users discussion. > > Hdf-forum@lists.hdfgroup.org > > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > > Twitter: [x.com](https://twitter.com/hdf5) ---
**Author:** ![David1](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/73ab20/32.png) [@David1](https://forum.hdfgroup.org/u/David1)\ **Post date:** [February 17, 2016, 6:22am UTC](https://forum.hdfgroup.org/t/boolean-values/3683/9 "2016-02-17T06:22:53Z")
Hi Daniel, It turns out I just didn't fully understand the n-bit types and filters yet. The bit types always store in bytes in but then the filter will pack things further on read/write. So I got what I wanted working with bytes in memory but bits on disk for bool data sets. Thanks again for your suggestions. David > **···** > > On Sat, Feb 13, 2016 at 2:35 PM, David \ wrote: > > > Daniel. > > > > It looks like HDF5 data types are all sized in bytes. So while you can > > define a 1 bit type it is always stored as a byte. I guess I need to make > > my own packer. > > > > I will however use the N-bit stuff for another issue I have which is > > 24-bit data. Much more straight forward. > > > > David > > > > On Thu, Feb 11, 2016 at 8:39 AM, David \ wrote: > > > > > That looks perfect. Thank you so much. Do you know what is the purpose of > > > the H5T\_NATIVE\_Bxx types? ---
**Author:** ![David1](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/73ab20/32.png) [@David1](https://forum.hdfgroup.org/u/David1)\ **Post date:** [February 17, 2016, 8:04pm UTC](https://forum.hdfgroup.org/t/boolean-values/3683/10 "2016-02-17T20:04:29Z")
Hi Elena, What I don't understand is how H5T\_NATIVE\_B32 is different from H5T\_NATIVE\_UINT32. David > **···** > > On Wed, Feb 17, 2016 at 10:43 AM, Elena Pourmal \ wrote: > > > David, > > > > On Feb 11, 2016, at 10:39 AM, David \ wrote: > > > > \> That looks perfect. Thank you so much. Do you know what is the purpose > > of the H5T\_NATIVE\_Bxx types? > > Good question 🙂 > > > > B stands for bitfield. See > > [https://www.hdfgroup.org/HDF5/doc1.6/Datatypes.htm](https://www.hdfgroup.org/HDF5/doc1.6/Datatypes.htm), Section 6 and current > > [https://www.hdfgroup.org/HDF5/doc/RM/PredefDTypes.html](https://www.hdfgroup.org/HDF5/doc/RM/PredefDTypes.html) > > > > Elena > > \> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > > \> Hdf-forum is for HDF software users discussion. > > \> Hdf-forum@lists.hdfgroup.org > > \> [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > > \> Twitter: [x.com](https://twitter.com/hdf5) > > > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > > Hdf-forum is for HDF software users discussion. > > Hdf-forum@lists.hdfgroup.org > > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > > Twitter: [x.com](https://twitter.com/hdf5) ---
**Author:** ![epourmal](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/e/c67d28/32.png) [@epourmal](https://forum.hdfgroup.org/u/epourmal)\ **Post date:** [February 18, 2016, 4:35am UTC](https://forum.hdfgroup.org/t/boolean-values/3683/11 "2016-02-18T04:35:46Z")
David, Integer type can be converted by the HDF5 library to other numeric types; bitfield cannot be converted. I hope other HDF folks will chime in if I am wrong. Elena > **···** > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Elena Pourmal The HDF Group [http://hdfgroup.org](http://hdfgroup.org) > 1800 So. Oak St., Suite 203, Champaign IL 61820 > 217.531.6112 > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > On Feb 17, 2016, at 2:04 PM, David \\> wrote: > > Hi Elena, > > What I don't understand is how H5T\_NATIVE\_B32 is different from H5T\_NATIVE\_UINT32. > > David > > On Wed, Feb 17, 2016 at 10:43 AM, Elena Pourmal \\> wrote: > David, > > On Feb 11, 2016, at 10:39 AM, David \\> wrote: > > > That looks perfect. Thank you so much. Do you know what is the purpose of the H5T\_NATIVE\_Bxx types? > > Good question 🙂 > > B stands for bitfield. See [https://www.hdfgroup.org/HDF5/doc1.6/Datatypes.htm](https://www.hdfgroup.org/HDF5/doc1.6/Datatypes.htm), Section 6 and current [https://www.hdfgroup.org/HDF5/doc/RM/PredefDTypes.html](https://www.hdfgroup.org/HDF5/doc/RM/PredefDTypes.html) > > Elena > > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > > Hdf-forum is for HDF software users discussion. > > Hdf-forum@lists.hdfgroup.org\ > > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > > Twitter: [x.com](https://twitter.com/hdf5) > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > Hdf-forum is for HDF software users discussion. > Hdf-forum@lists.hdfgroup.org\ > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > Twitter: [x.com](https://twitter.com/hdf5) > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > Hdf-forum is for HDF software users discussion. > Hdf-forum@lists.hdfgroup.org\ > [http://lists.hdfgroup.org/mailman/listinfo/hdf-forum\_lists.hdfgroup.org](http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org) > Twitter: [x.com](https://twitter.com/hdf5) ---
**Author:** ![Dan](https://forum.hdfgroup.org/letter_avatar_proxy/v4/letter/d/eada6e/32.png) [@Dan](https://forum.hdfgroup.org/u/Dan)\ **Post date:** [February 17, 2016, 9:50am UTC](https://forum.hdfgroup.org/t/boolean-values/3683/12 "2016-02-17T09:50:13Z")
Hi, Good to know that works! If you anticipate having a large dataset of bits, you might also want to try enabling the deflate filter \*after\* the n-bit filter to make the size on disk even smaller. Cheers, > **···** > > From: Hdf-forum [[mailto:hdf-forum-bounces@lists.hdfgroup.org](mailto:hdf-forum-bounces@lists.hdfgroup.org)] On Behalf Of David > Sent: 17 February 2016 06:23 > To: HDF Users Discussion List > Subject: Re: [Hdf-forum] Boolean values > > Hi Daniel, > It turns out I just didn't fully understand the n-bit types and filters yet. The bit types always store in bytes in but then the filter will pack things further on read/write. So I got what I wanted working with bytes in memory but bits on disk for bool data sets. Thanks again for your suggestions. > David > > On Sat, Feb 13, 2016 at 2:35 PM, David \<[list@aue.org](mailto:list@aue.org)\<[mailto:list@aue.org](mailto:list@aue.org)\>\> wrote: > Daniel. > > It looks like HDF5 data types are all sized in bytes. So while you can define a 1 bit type it is always stored as a byte. I guess I need to make my own packer. > I will however use the N-bit stuff for another issue I have which is 24-bit data. Much more straight forward. > > David > > On Thu, Feb 11, 2016 at 8:39 AM, David \<[list@aue.org](mailto:list@aue.org)\<[mailto:list@aue.org](mailto:list@aue.org)\>\> wrote: > That looks perfect. Thank you so much. Do you know what is the purpose of the H5T\_NATIVE\_Bxx types?