Re: [Pytables-users] searching for group names
Hi, I don't know if this is related in any way to Gergo's problem, but I have slow responses when querying which children a group contains, if that group contains big leafs. I am using pytables 2.5 and hdf5 1.8.9 on linux 64 bit. Specifically, I found that using the _g_get_objinfo method (which is used by other methods that I use) is slow when used on a large leaf. The slowness is proportional to the size of the leaf. It is almost as if some process is actually reading the data instead of just info on the type of data. I am noticing this because my data is on an external usb3 disk. To give you an idea: that method takes almost 80 seconds to return the string 'Leaf' when used on a 5 Gb EArray. That should roughly correspond to reading the complete disk-based array. The info is cached somehow, because if I run the method a second time in the same python session it is very fast. If I copy my hdf5 file to my SSD disk, things are much faster, but running the method still takes 2 seconds or so on a 5 Gb leaf. Is this expected behavior and should I just avoid this method in my applications, or is something wrong? Best, Gabriel Anthony Scopatz scop...@gmail.com schreef: On Mon, Aug 5, 2013 at 4:11 AM, Nyirő Gergő gergo.ny...@gmail.com wrote: Hello, We develop a measurement evaluation tool, and we'd like to use pytables/hdf5 as a middle layer for signal accessing. We have to deal with the silly structure of the recorder device measurement format. The signals can be accessed via two identifiers: * device name: source of the signal-channel of the message-another tag-yet another tag * signal name The first identifier says the source information of the signal, which can be quite long. Therefore I grouped the device name into two layers: /source of the signal /channel of the message... /signal name So if you have the same message from two channels, than you will get /foo-device-name /channel-1 /bar /baz /channel-2 /bar /baz Besides signal loading, we have to search for signal name as fast as possible, and return with the shortest unique device name part and the signal name. Using the structure above, iterating over the group names is quite slow. So I build up a table from device and signal name. As far as I know, the pytables query does not support string searching (e.g. startswidth, *foo[0-9]ch*, etc.), so fetching this table lead us to a pure python loop which is slow again. Therefore I build up a python dictionary from the table, which provide fast iteration against the table, but the init time increased from 100 ms to 3-4 sec (we have more than 40 000 signals). Do you have any advice how to search for group names in hdf5 with pytables in an efficient way? Hi grego, Searching through group names, like accessing all HDF5 metadata, is slow. For group names this is because rather than searching through a list you are traversing a B-tree, IIRC. So you have to use the couple of tricks that you used: 1) have another Table / Array of all table names, 2) read this in once to a native Python data structure (dict here). However, 4 sec to read in this table seems excessive for data of this size. You are probably not reading this in properly. You should be using: raw_grps = f.root.grp_names[:] or similar. Maybe other people have some other ideas. Be Well Anthony ps: I would be most happy with a glob interface. thanks for your advices in advance, gergo -- Get your SQL database under version control now! Version control is standard for application code, but databases havent caught up. So what steps can you take to put your SQL databases under version control? Why should you start doing it? Read more to find out. http://pubads.g.doubleclick.net/gampad/clk?id=49501711iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
[Pytables-users] should I use pytables?
Dear all, I have a hierachical nested python dictionaries with the end of the branch as either pandas dataframe, or np.ndarray or list or plain scalars. let's say the different levels of keys are: 1st level: ['top1', 'top2', 'top3'] 2nd level: ['mid1','mid2','mid3'] 3rd level: ['bot1','bot2','bot3','bot4'] I think I am looking for some data strucuture that allow easy retrieving of the data at different levels as dictionaries (I cannot think out something better yet). for example: data.ix['top1',:,'bot1'] will have keys only at the middle levels. I have a quick look of pytables document but not very sure, should I use pytables for this purpose? thanks a lot for any idea. cheers, Chao -- *** Chao YUE Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL) UMR 1572 CEA-CNRS-UVSQ Batiment 712 - Pe 119 91191 GIF Sur YVETTE Cedex Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16 -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
[Pytables-users] suitable for storing data like k-v style?
Hi all, I'm developing data processing service and evaluating if Pytable. Since hdf5 supports hierarchical data like a tree of folder, can I use such a tree-like structure as a K-V store like possibly store million of tables or arrays under one group and randomly access any one of them in O(1) time? e.g. root/ user_log/ uid1- table / array, (of tens of thousand rows / elements, ETL'ed user log info in int format) uid2- table / array, uid3- table / array, uid4- table / array, uid5- table / array, …… (perhaps million user) Just wondering how the hierarchical structure is implemented and such usage pattern is supported? if no, is there any running or better way to store such type of information? We adopt Pytables because the data is stored in higher density, faster loaded and no ACID / concurrency overhead, so traditional DB and no-sql db is not our option.. Thanks, Jason -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
Re: [Pytables-users] should I use pytables?
Thanks Anthony, I think I will give a try, apprently at some stage I would like to flush the data into disk :p cheers, Chao On Wed, Aug 7, 2013 at 6:44 PM, Anthony Scopatz scop...@gmail.com wrote: On Wed, Aug 7, 2013 at 5:44 AM, Chao YUE chaoyue...@gmail.com wrote: Dear all, I have a hierachical nested python dictionaries with the end of the branch as either pandas dataframe, or np.ndarray or list or plain scalars. let's say the different levels of keys are: 1st level: ['top1', 'top2', 'top3'] 2nd level: ['mid1','mid2','mid3'] 3rd level: ['bot1','bot2','bot3','bot4'] I think I am looking for some data strucuture that allow easy retrieving of the data at different levels as dictionaries (I cannot think out something better yet). for example: data.ix['top1',:,'bot1'] will have keys only at the middle levels. I have a quick look of pytables document but not very sure, should I use pytables for this purpose? Hello Chao, If you are only ever going to use this data structure in memory, you shouldn't use pytables. If you are going to persist this information to disk than pytables is a great choice! Every dictionary will become a group and every leaf data structure will become an Array or a Table. Be Well Anthony thanks a lot for any idea. cheers, Chao -- *** Chao YUE Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL) UMR 1572 CEA-CNRS-UVSQ Batiment 712 - Pe 119 91191 GIF Sur YVETTE Cedex Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16 -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- *** Chao YUE Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL) UMR 1572 CEA-CNRS-UVSQ Batiment 712 - Pe 119 91191 GIF Sur YVETTE Cedex Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16 -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
Re: [Pytables-users] suitable for storing data like k-v style?
Hi Jason, A key-value store pattern is definitely supported. However, be forewarned that groups are implemented using B-trees, not hash tables. However, with data of your size most of the access time will be in the leaf nodes and not getting the group. I'd say try it out and see. Be Well Anthony On Wed, Aug 7, 2013 at 11:33 AM, Xianli Xu xiaolou.c...@gmail.com wrote: Hi all, I'm developing data processing service and evaluating if Pytable. Since hdf5 supports hierarchical data like a tree of folder, can I use such a tree-like structure as a K-V store like possibly store million of tables or arrays under one group and randomly access any one of them in O(1) time? e.g. root/ user_log/ uid1- table / array, (of tens of thousand rows / elements, ETL'ed user log info in int format) uid2- table / array, uid3- table / array, uid4- table / array, uid5- table / array, …… (perhaps million user) Just wondering how the hierarchical structure is implemented and such usage pattern is supported? if no, is there any running or better way to store such type of information? We adopt Pytables because the data is stored in higher density, faster loaded and no ACID / concurrency overhead, so traditional DB and no-sql db is not our option.. Thanks, Jason -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk ___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users -- Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with 2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031iu=/4140/ostg.clktrk___ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
[Pytables-users] Numpy Arrays to Structure Array or Table
Hi there,
I have some generic functions that take time series data with 2 numpy array
arguments, time and value, and return 2 numpy arrays of time and value.
I would like to place these arrays into a Numpy structured array or
directly into a new pytables table with fields, time and value.
Now Ive found I could do this:
t, v = some_func(t, v)
A = np.empty(len(t), dtype=[('time', np.float64), ('value',
np.float64)])
A['time'] = t
A['value'] = v
hfile.createTable(grp, 'signal', description=A)
hfile.flush()
But this seems rather clunky and inefficient. Any suggestions to make this
repackaging a little smoother?
--
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