diff --git a/libsrc4/nc4var.c b/libsrc4/nc4var.c index 4f9f04160..49e1b2c0e 100644 --- a/libsrc4/nc4var.c +++ b/libsrc4/nc4var.c @@ -324,6 +324,74 @@ nc4_find_default_chunksizes(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var) return NC_NOERR; } +/* Find the default chunk nelems (i.e. length of chunk along each + * dimension). */ +static int +nc4_find_default_chunksizes2(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var) +{ + int d; + size_t type_size; + float num_values = 1, num_set = 0; + float total_chunk_size; + int retval; + + if (var->type_info->nc_typeid == NC_STRING) + type_size = sizeof(char *); + else + type_size = var->type_info->size; + + /* Later this will become the total number of bytes in the default + * chunk. */ + total_chunk_size = type_size; + + /* How many values in the variable (or one record, if there are + * unlimited dimensions); which is the largest dimension, and how + * long is it? */ + for (d = 0; d < var->ndims; d++) + { + assert(var->dim[d]); + if (var->dim[d]->len) + num_values *= (float)var->dim[d]->len; + else + num_set++; + + LOG((4, "d %d num_values %f", d, num_values)); + } + + /* Pick a chunk length for each dimension, if one has not already + * been picked above. */ + for (d = 0; d < var->ndims; d++) + if (!var->chunksizes[d]) + { + size_t suggested_size; + suggested_size = (pow((double)DEFAULT_CHUNK_SIZE/(num_values * type_size), + 1/(double)(var->ndims - num_set)) * var->dim[d]->len - .5); + if (suggested_size > var->dim[d]->len) + suggested_size = var->dim[d]->len; + var->chunksizes[d] = suggested_size ? suggested_size : 1; + total_chunk_size *= var->chunksizes[d]; + LOG((4, "nc_def_var_nc4: name %s dim %d DEFAULT_CHUNK_SIZE %d num_values %f type_size %d " + "chunksize %ld", var->name, d, DEFAULT_CHUNK_SIZE, num_values, type_size, var->chunksizes[d])); + } + LOG((4, "total_chunk_size %f", total_chunk_size)); + + /* But did this add up to a chunk that is too big? */ + retval = check_chunksizes(grp, var, var->chunksizes); + if (retval) + { + /* Other error? */ + if (retval != NC_EBADCHUNK) + return retval; + + /* Chunk is too big! Reduce each dimension by half and try again. */ + for ( ; retval == NC_EBADCHUNK; retval = check_chunksizes(grp, var, var->chunksizes)) + for (d = 0; d < var->ndims; d++) + var->chunksizes[d] = var->chunksizes[d]/2 ? var->chunksizes[d]/2 : 1; + } + + return NC_NOERR; +} + /* This is called when a new netCDF-4 variable is defined. Break it * down! */ static int @@ -487,7 +555,7 @@ nc_def_var_nc4(int ncid, const char *name, nc_type xtype, if (!(var->chunksizes = calloc(var->ndims, sizeof(size_t)))) return NC_ENOMEM; - if ((retval = nc4_find_default_chunksizes(grp, var))) + if ((retval = nc4_find_default_chunksizes2(grp, var))) return retval; /* Is this a variable with a chunksize greater than the current @@ -858,7 +926,7 @@ nc_def_var_extra(int ncid, int varid, int *shuffle, int *deflate, { /* Determine default chunksizes for this variable. */ if (!var->chunksizes[0]) - if ((retval = nc4_find_default_chunksizes(grp, var))) + if ((retval = nc4_find_default_chunksizes2(grp, var))) return retval; /* Adjust the cache. */