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108dc0f01d
re: https://github.com/Unidata/netcdf-c/issues/972 The current szip plugin code in the HDF5 library has some unexpected behaviors that require some changes to how nc_inq_var_szip is implemented and to the corresponding tests: nc_test4/{test_szip,tst_vars3}. Specifically, the following can happen: 1. The number of parameters provided by the user will be two, but the number of parameters returned by nc_inq_var_filter will be four because the HDF5 code (H5Zszip) will add two extra parameters for internal use. It turns out that the two parameters provided when calling nc_def_var_filter correspond to the first two parameters of the four parameters returned by nc_inq_var_filter. 2. The nc_inq_var_szip values corresponding to the ones provided by the caller may be different than those provided by nc_def_var_filter. The value of the options_mask argument is known to add additional flag bits, and the pixels_per_block parameter may be modified.
157 lines
3.7 KiB
C
157 lines
3.7 KiB
C
/* This is part of the netCDF package.
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Copyright 2005 University Corporation for Atmospheric Research/Unidata
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See COPYRIGHT file for conditions of use.
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*/
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/*
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* Example illustrates the use of SZIP compression in netCDF5
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* Taken from HDF5 example.
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include "nc_tests.h"
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#include "err_macros.h"
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#include "netcdf.h"
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#undef PLAIN
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#define USECLOSE
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/* Szip Constants. */
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#define HDF5_FILTER_SZIP 4
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#define H5_SZIP_MAX_PIXELS_PER_BLOCK_IN 32
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#define H5_SZIP_MAX_PIXELS_PER_BLOCK_OUT 64
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/* Option Mask Flags (Refere to HDF5 szip documentation) */
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#define H5_SZIP_ALLOW_K13_OPTION_MASK 1 /*Allows k split = 13 compression mode. (Default)*/
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#define H5_SZIP_CHIP_OPTION_MASK 2 /*Compresses exactly as in hardware*/
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#define H5_SZIP_EC_OPTION_MASK 4 /*Selects entropy coding method. (Default)*/
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#define H5_SZIP_NN_OPTION_MASK 32 /*Selects nearest neighbor coding method*/
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#define NX 500
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#define NY 600
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#define CH_NX 100
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#define CH_NY 25
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static void initialize(void);
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static int compare(void);
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static float buf[NX][NY];
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static float buf_r[NX][NY];
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int
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main(void)
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{
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int ncid, varid, dimids[2];
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size_t dims[2], chunk_size[2];
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unsigned int szip_params[2]; /* [0]=options_mask [1]=pixels_per_block */
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int errcnt = 0;
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/* Create a new file using read/write access. */
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if(nc_create("testszip.nc", NC_CLOBBER|NC_NETCDF4, &ncid)) ERR;
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/* Create dims */
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dims[0] = NX;
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dims[1] = NY;
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if(nc_def_dim(ncid, "x", dims[0], &dimids[0])) ERR;
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if(nc_def_dim(ncid, "y", dims[1], &dimids[1])) ERR;
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/* Create a dimensioned variable */
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if(nc_def_var(ncid, "datasetF32", NC_FLOAT, 2, dimids, &varid)) ERR;
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/* no fill */
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if(nc_def_var_fill(ncid, varid, 1, NULL)) ERR;
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/* Define chunking for the variable:
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* the raw data is to be partitioned into 100x100 element chunks.
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*/
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chunk_size[0] = CH_NX;
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chunk_size[1] = CH_NY;
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if(nc_def_var_chunking(ncid, varid, NC_CHUNKED, chunk_size)) ERR;
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#ifndef PLAIN
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/*
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* Set parameters for SZIP compression; check the description of
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* the H5Pset_szip function in the HDF5 Reference Manual for more
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* information.
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*/
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szip_params[0] = H5_SZIP_NN_OPTION_MASK;
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szip_params[1] = H5_SZIP_MAX_PIXELS_PER_BLOCK_IN;
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{ int stat = nc_def_var_filter(ncid, varid, HDF5_FILTER_SZIP, 2, szip_params);
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if(stat) {
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fprintf(stderr,"XXX: %d %s\b",stat,nc_strerror(stat));
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ERR;
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}
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}
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#endif
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if(nc_enddef(ncid)) ERR;
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initialize();
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/* Write the array to the file */
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if(nc_put_var_float(ncid, varid, &buf[0][0])) ERR;
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#ifdef USECLOSE
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/* Close and re-open the file */
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if(nc_close(ncid)) ERR;
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if(nc_open("testszip.nc", NC_NETCDF4, &ncid)) ERR;
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if(nc_inq_varid(ncid, "datasetF32", &varid)) ERR;
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#endif
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/*
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* Read the array. This is similar to writing data,
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* except the data flows in the opposite direction.
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* Note: Decompression should be automatic.
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*/
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memset(buf_r,0,sizeof(buf_r));
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if(nc_get_var_float(ncid, varid, &buf_r[0][0])) ERR;
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/* Do comparison */
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errcnt = compare();
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if(nc_close(ncid)) ERR;
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if(errcnt) ERR;
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SUMMARIZE_ERR;
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FINAL_RESULTS;
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return (errcnt==0?0:1);
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}
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static int
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compare()
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{
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int i,j;
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int errs = 0;
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/* Do comparison */
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for (i=0; i < NX; i++) {
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for (j=0; j < NY; j++) {
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if(buf[i][j] != buf_r[i][j]) {
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errs++;
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printf("mismatch: [%d][%d]: write = %f read=%f\n",
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i,j,buf[i][j],buf_r[i][j]);
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}
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}
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}
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return errs;
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}
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static void
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initialize(void)
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{
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int i, j;
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/* Initialize data buffer with some bogus data. */
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for(i=0; i < NX; i++) {
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for(j=0; j < NY; j++) {
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buf[i][j] = (float)(i + j);
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}
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}
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}
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