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Format for raw output files from MITgcmUV |
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========================================= |
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|
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Introduction |
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------------ |
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When running in parallel mode with multiple processes the MITgcmUV |
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model operates as N separate programs, each responsible for its "local" |
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region of the "total" model domain. Synchronisation and sharing of data between |
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these processes is done explicitly by calls to data exchange and |
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barrier routines. Consequently there is no single program that has |
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a view of the whole model domain as the code is running. Any simple |
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I/O can only operate on the local region of the model domain - I/O |
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operations to and from datasets that represent the total domain need |
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to address the multiple process behavior explicitly. |
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Under MITgcmUV there are a set of I/O support routines that mask the |
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details of this process and enable end-users to read and write datasets |
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in a straight-forward manner. The routines use the following design |
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strategy: |
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o Input datasets are for the total domain |
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o Output datasets are for the local domain |
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o A separate program "joinds" is provided which joins a set of |
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local domain datasets together to form total model domain dataset. |
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|
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MITgcmUV IO support routines |
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---------------------------- |
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- READ_FLD_XY_RS |
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- READ_FLD_XY_RL |
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- READ_FLD_XYZ_RS |
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- READ_FLD_XYZ_RL |
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|
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- WRITE_FLD_XY_RS |
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- WRITE_FLD_XY_RL |
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- WRITE_FLD_XYZ_RS |
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- WRITE_FLD_XYZ_RL |
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|
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Dataset format |
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-------------- |
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Datasets are written using the standard Fortran 77 sequential binary |
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file format. The Fortran IO statements in he model code do not specify any |
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particular format, however, compile and run-time flags are used on some platforms. |
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On DEC platforms by default the IO form is set to big-endian with a compile time |
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flag. On CRAY platforms a runtime flag is normally used to select IEEE |
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representation. The Fortran 77 sequential binary file format is |
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4 byte header |
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data |
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4 byte terminator |
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The header and terminator are unsigned integers which give the length |
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of the data section in bytes. This is format is standard over all UNIX |
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platforms. In Fortran this style of file is generated by code of the |
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form |
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|
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REAL A(dim1, dim2, ..... ) |
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OPEN(unitnumber,filename,FORM='FORMATTED') |
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WRITE(unitnumber) A |
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END |
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|
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The data is sequenced in the standard Fortran convention of the left-most |
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index varying fastest. This convention holds for any dimension of datsets |
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one-dimensional, two-dimensional, three-dimensional and four-dimensional or |
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more datasets are all written this way. |
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|
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Multiprocess support |
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-------------------- |
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The format described above is used for multi-process simulations. In this |
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case the data written to separate files with each process writing data that |
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is local to it. To support this approach a file naming convention is used and a second |
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file of "meta" information accompanines the data. The naming convention |
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is used to avoid duplicate names and to make it easy to identify sets of |
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files that together represent the total domain data. The meta file contains |
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information about the extent of the sub-domain within each file. |
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The naming convention used is |
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PREF.SUFF.pPNUMBER.tTNUMBER.data |
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PREF.SUFF.pPNUMBER.tTNUMBER.meta |
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|
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where |
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PREF - Is a field identifying the data within the file. For |
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temperature PREF is T, for zonal velocity PREF is U etc... |
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SUFF - Is a field identifying the "instance" of the data within the |
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file. The instance is typically the time level. In general |
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the instance will be a model timestep number. |
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PNUMBER - Is a process number used to identitfy which process of |
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a multi-process run generated this data. The number ranges |
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from 0 to (number of processors)-1. |
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TNUMBER - Is a thread number used to identify which thread of a |
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multi-threaded run generated this data. The number ranges |
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from 0 to (number of threads)-1. |
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|
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the .data suffix identifies the file containing the actual data. |
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the .meta suffix identifies the file containing textual information |
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indicating the extent of the domain written to the .data file. |
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|
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.meta file Format |
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----------------- |
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This file contains a set of parameters that are specified using the |
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generic parameter specification format used in GCMPACK software. This |
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format consists of a sequence of assignments and comments |
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Assignments have the form |
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keyword =[ val-list ]; |
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|
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where |
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keyword is a text string |
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val-list is a sequence of one or more fields separated by commas |
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|
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Comments are preceeded by // or # characters or contained in |
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/* */ pairs. |
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The keywords contained in a .meta file are |
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id - This is a numeric identifier. It can be used to |
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verify consistency over a set of .meta files. |
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nDims - This is a single integer indicating the dimensionality |
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of the data in the .data file. |
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dimList - This is a sequence of triplets. There is one triplet for |
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each dimension and the triplets are ordered in the same |
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way as the dimensions. Each triplet is made of three integers. |
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The first integer gives the domain extent globally for |
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the associated dimension. |
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The second integer gives the low coordinate for the values |
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within .data file for the associated dimension. |
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The third integer gives the high coordinate for the values |
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within .data file for the associated dimension. |
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Thus for a .data file containing the north-west quadrant of |
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a global domain of size 90 x 40 the .meta might read |
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nDims = [ 2 ]; |
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dimList = [ 90, 46, 90, 40, 1, 20]; |
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For a global domain of size 90 x 40 x 33 the .meta file |
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would read |
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nDims = [ 3 ]; |
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dimList = [ 90, 46, 90, 40, 1, 20, 33, 1, 33]; |
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|
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|
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|
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Example matlab program to join files |
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------------------------------------ |
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The following matlab script joins together a collection of files that |
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were written in split form. The files to join are indicated by a user |
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defined PREF.SUFF pair. e.g. T.0000002800. The script uses the UNIX |
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ls command to find all files starting with T.0000002800 and then |
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scans the .meta files to extract the dimensions. It then merges all |
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the sections together to form a complete representation of the global |
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dataset. |
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>> function [AA] = rdmeta(fname,varargin) |
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>> % |
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>> % Read MITgcmUV Meta/Data files |
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>> % |
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>> % A = RDMETA(FNAME) reads data described by meta/data file format. |
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>> % FNAME is a string containing the "head" of the file names. |
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>> % |
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>> % eg. To load the meta-data files |
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>> % T.0000002880.p0000.t0000.meta, T.0000002880.p0000.t0000.data |
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>> % T.0000002880.p0001.t0000.meta, T.0000002880.p0001.t0000.data |
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>> % T.0000002880.p0002.t0000.meta, T.0000002880.p0002.t0000.data |
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>> % T.0000002880.p0003.t0000.meta, T.0000002880.p0003.t0000.data |
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>> % use |
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>> % >> A=rdmeta('T.0000002880'); |
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>> % |
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>> % A = RDMETA(FNAME,MACHINEFORMAT) allows the machine format to be specified |
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>> % which MACHINEFORMAT is on of the following strings: |
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>> % |
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>> % 'native' or 'n' - local machine format - the default |
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>> % 'ieee-le' or 'l' - IEEE floating point with little-endian |
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>> % byte ordering |
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>> % 'ieee-be' or 'b' - IEEE floating point with big-endian |
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>> % byte ordering |
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>> % 'vaxd' or 'd' - VAX D floating point and VAX ordering |
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>> % 'vaxg' or 'g' - VAX G floating point and VAX ordering |
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>> % 'cray' or 'c' - Cray floating point with big-endian |
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>> % byte ordering |
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>> % 'ieee-le.l64' or 'a' - IEEE floating point with little-endian |
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>> % byte ordering and 64 bit long data type |
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>> % 'ieee-be.l64' or 's' - IEEE floating point with big-endian byte |
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>> % ordering and 64 bit long data type. |
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>> % |
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>> |
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>> % Default options |
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>> ieee='n'; |
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>> |
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>> % Check optional arguments |
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>> args=char(varargin); |
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>> while (size(args,1) > 0) |
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>> if deblank(args(1,:)) == 'n' | deblank(args(1,:)) == 'native' |
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>> ieee='n'; |
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>> elseif deblank(args(1,:)) == 'l' | deblank(args(1,:)) == 'ieee-le' |
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>> ieee='l'; |
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>> elseif deblank(args(1,:)) == 'b' | deblank(args(1,:)) == 'ieee-be' |
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>> ieee='b'; |
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>> elseif deblank(args(1,:)) == 'c' | deblank(args(1,:)) == 'cray' |
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>> ieee='c'; |
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>> elseif deblank(args(1,:)) == 'a' | deblank(args(1,:)) == 'ieee-le.l64' |
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>> ieee='a'; |
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>> elseif deblank(args(1,:)) == 's' | deblank(args(1,:)) == 'ieee-be.l64' |
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>> ieee='s'; |
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>> else |
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>> sprintf(['Optional argument ' args(1,:) ' is unknown']) |
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>> return |
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>> end |
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>> args=args(2:end,:); |
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>> end |
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>> |
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>> % Match name of all meta-files |
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>> eval(['ls ' fname '*.meta;']); |
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>> allfiles=ans; |
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>> |
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>> % Beginning and end of strings |
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>> Iend=findstr(allfiles,'.meta')+4; |
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>> Ibeg=[1 Iend(1:end-1)+2]; |
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>> |
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>> % Loop through allfiles |
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>> for j=1:prod(size(Ibeg)), |
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>> |
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>> % Read meta- and data-file |
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>> [A,N] = localrdmeta(allfiles(Ibeg(j):Iend(j)),ieee); |
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>> |
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>> bdims=N(1,:); |
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>> r0=N(2,:); |
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>> rN=N(3,:); |
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>> ndims=prod(size(bdims)); |
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>> if (ndims == 1) |
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>> AA(r0(1):rN(1))=A; |
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>> elseif (ndims == 2) |
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>> AA(r0(1):rN(1),r0(2):rN(2))=A; |
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>> elseif (ndims == 3) |
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>> AA(r0(1):rN(1),r0(2):rN(2),r0(3):rN(3))=A; |
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>> elseif (ndims == 4) |
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>> AA(r0(1):rN(1),r0(2):rN(2),r0(3):rN(3),r0(4):rN(4))=A; |
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>> else |
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>> sprintf('Dimension of data set is larger than currently coded. Sorry!') |
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>> return |
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>> end |
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>> |
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>> end |
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>> |
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>> %------------------------------------------------------------------------------- |
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>> |
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>> function [A,N] = localrdmeta(fname,ieee) |
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>> |
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>> mname=fname; |
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>> dname=strrep(mname,'.meta','.data'); |
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>> |
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>> % Read and interpret Meta file |
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>> fid = fopen(mname,'r'); |
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>> if (fid == -1) |
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>> sprintf(['Fila e' mname ' could not be opened']) |
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>> return |
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>> end |
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>> |
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>> % Scan each line of the Meta file |
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>> allstr=' '; |
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>> keepgoing = 1; |
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>> while keepgoing > 0, |
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>> line = fgetl(fid); |
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>> if (line == -1) |
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>> keepgoing=-1; |
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>> else |
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>> % Strip out "(PID.TID *.*)" by finding first ")" |
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>> ind=findstr([line ')'],')'); line=line(ind(1)+1:end); |
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>> % Remove comments of form // |
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>> line=[line ' //']; ind=findstr(line,'//'); line=line(1:ind(1)-1); |
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>> % Add to total string |
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>> allstr=[allstr line]; |
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>> end |
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>> end |
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>> |
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>> % Close meta file |
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>> fclose(fid); |
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>> |
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>> % Strip out comments of form /* ... */ |
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>> ind1=findstr(allstr,'/*'); ind2=findstr(allstr,'*/'); |
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>> if size(ind1) ~= size(ind2) |
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>> sprintf('The /* ... */ comments are not properly paired') |
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>> return |
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>> end |
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>> while size(ind1,2) > 0 |
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>> allstr=[allstr(1:ind1(1)-1) allstr(ind2(1)+3:end)]; |
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>> ind1=findstr(allstr,'/*'); ind2=findstr(allstr,'*/'); |
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>> end |
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>> |
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>> eval(lower(allstr)); |
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>> |
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>> N=reshape( dimlist , 3 , prod(size(dimlist))/3 ); |
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>> |
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>> A=allstr; |
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>> % Open data file |
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>> fid=fopen(dname,'r',ieee); |
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>> |
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>> % Read record size in bytes |
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>> recsz=fread(fid,1,'uint32'); |
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>> ldims=N(3,:)-N(2,:)+1; |
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>> numels=prod(ldims); |
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>> |
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>> rat=recsz/numels; |
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>> if rat == 4 |
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>> A=fread(fid,numels,'real*4'); |
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>> elseif rat == 8 |
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>> A=fread(fid,numels,'real*8'); |
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>> else |
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>> sprintf('Ratio between record size and size in meta-file inconsistent') |
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>> sprintf(' Implied size in meta-file = %d', numels ) |
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>> sprintf(' Record size in data-file = %d', recsz ) |
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>> return |
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>> end |
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>> |
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>> erecsz=fread(fid,1,'uint32'); |
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>> if erecsz ~= recsz |
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>> sprintf('WARNING: Record sizes at beginning and end of file are inconsistent') |
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>> end |
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>> |
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>> fclose(fid); |
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>> |
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>> A=reshape(A,ldims); |
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>> |
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