/* Like tensor_compress, but also compress into one dimension any
group of dimensions that form a contiguous block of indices with
some stride. (This can safely be done for transform vector sizes.) */
tensor *X(tensor_compress_contiguous)(const tensor *sz)
{
int i, rnk;
tensor *sz2, *x;
if (X(tensor_sz)(sz) == 0)
return X(mktensor)(RNK_MINFTY);
sz2 = X(tensor_compress)(sz);
A(FINITE_RNK(sz2->rnk));
if (sz2->rnk < 2) /* nothing to compress */
return sz2;
for (i = rnk = 1; i < sz2->rnk; ++i)
if (!strides_contig(sz2->dims + i - 1, sz2->dims + i))
++rnk;
x = X(mktensor)(rnk);
x->dims[0] = sz2->dims[0];
for (i = rnk = 1; i < sz2->rnk; ++i) {
if (strides_contig(sz2->dims + i - 1, sz2->dims + i)) {
x->dims[rnk - 1].n *= sz2->dims[i].n;
x->dims[rnk - 1].is = sz2->dims[i].is;
x->dims[rnk - 1].os = sz2->dims[i].os;
} else {
A(rnk < x->rnk);
x->dims[rnk++] = sz2->dims[i];
}
}
X(tensor_destroy)(sz2);
return x;
}
/* Like tensor_compress, but also compress into one dimension any
group of dimensions that form a contiguous block of indices with
some stride. (This can safely be done for transform vector sizes.) */
tensor *X(tensor_compress_contiguous)(const tensor *sz)
{
int i, rnk;
tensor *sz2, *x;
if (X(tensor_sz)(sz) == 0)
return X(mktensor)(RNK_MINFTY);
sz2 = really_compress(sz);
A(FINITE_RNK(sz2->rnk));
if (sz2->rnk <= 1) { /* nothing to compress. */
if (0) {
/* this call is redundant, because "sz->rnk <= 1" implies
that the tensor is already canonical, but I am writing
it explicitly because "logically" we need to canonicalize
the tensor before returning. */
canonicalize(sz2);
}
return sz2;
}
/* sort in descending order of |istride|, so that compressible
dimensions appear contigously */
qsort(sz2->dims, (unsigned)sz2->rnk, sizeof(iodim),
(int (*)(const void *, const void *))compare_by_istride);
/* compute what the rank will be after compression */
for (i = rnk = 1; i < sz2->rnk; ++i)
if (!strides_contig(sz2->dims + i - 1, sz2->dims + i))
++rnk;
/* merge adjacent dimensions whenever possible */
x = X(mktensor)(rnk);
x->dims[0] = sz2->dims[0];
for (i = rnk = 1; i < sz2->rnk; ++i) {
if (strides_contig(sz2->dims + i - 1, sz2->dims + i)) {
x->dims[rnk - 1].n *= sz2->dims[i].n;
x->dims[rnk - 1].is = sz2->dims[i].is;
x->dims[rnk - 1].os = sz2->dims[i].os;
} else {
A(rnk < x->rnk);
x->dims[rnk++] = sz2->dims[i];
}
}
X(tensor_destroy)(sz2);
/* reduce to canonical form */
canonicalize(x);
return x;
}
