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added overhang (not hangover) calculations to default chunksizes

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This commit is contained in:
Ed Hartnett 2011-02-14 19:15:36 +00:00
parent 3340b641fd
commit 8d91b49ad2
1 changed files with 30 additions and 3 deletions
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33
libsrc4/nc4var.c
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@ -329,8 +329,8 @@ nc4_find_default_chunksizes(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var)
static int
nc4_find_default_chunksizes2(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var)
{
int d;
size_t type_size;
int d, max_dim;
size_t type_size, max_len = 0;
float num_values = 1, num_set = 0;
float total_chunk_size;
int retval;
@ -355,9 +355,28 @@ nc4_find_default_chunksizes2(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var)
else
num_set++;
LOG((4, "d %d num_values %f", d, num_values));
if (var->dim[d]->len > max_len)
{
max_len = var->dim[d]->len;
max_dim = d;
}
LOG((4, "d = %d max_dim %d max_len %ld num_values %f", d, max_dim, max_len,
num_values));
}
/* If a dim is several orders of magnitude smaller than the max
* dimension, set it's chunk size to the full extent of the smaller
* dimension. */
#define NC_DIM_MULTIPLIER 1000
for (d = 0; d < var->ndims; d++)
if (var->dim[d]->unlimited)
var->chunksizes[d] = 1;
else if (!var->dim[d]->unlimited && var->dim[d]->len * NC_DIM_MULTIPLIER < max_len)
{
var->chunksizes[d] = var->dim[d]->len;
num_set++;
}
/* Pick a chunk length for each dimension, if one has not already
* been picked above. */
for (d = 0; d < var->ndims; d++)
@ -389,6 +408,14 @@ nc4_find_default_chunksizes2(NC_GRP_INFO_T *grp, NC_VAR_INFO_T *var)
var->chunksizes[d] = var->chunksizes[d]/2 ? var->chunksizes[d]/2 : 1;
}
/* Do we have any big data overhangs? They can be dangerous to
* babies, the elderly, or confused campers who have had too much
* beer. */
#define NC_ALLOWED_OVERHANG .1
for (d = 0; d < var->ndims; d++)
for ( ; var->dim[d]->len % var->chunksizes[d] > var->dim[d]->len * NC_ALLOWED_OVERHANG; )
var->chunksizes[d] -= var->dim[d]->len * NC_ALLOWED_OVERHANG;
return NC_NOERR;
}