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added a simple reversible block wise shuffle

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This commit is contained in:
Ahmet Inan 2023-03-28 11:44:15 +02:00
commit e55c2bc083
1 changed files with 42 additions and 0 deletions
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42
permute.hh
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@ -35,6 +35,48 @@ public:
}
};
template <int SIZE, int BLOCK>
class ReversibleBlockShuffle
{
static_assert(SIZE >= 2 * BLOCK, "SIZE not large enough");
static_assert(SIZE % BLOCK == 0, "BLOCK does not divide SIZE");
static constexpr int BLOCKS = SIZE / BLOCK;
int seq[SIZE-1];
public:
ReversibleBlockShuffle()
{
CODE::Xorshift32 prng;
for (int j = 0; j < BLOCKS; ++j) {
if (j < BLOCKS-1)
seq[BLOCK*j] = j + prng() % (BLOCKS - j);
for (int i = 0; i < BLOCK-1; ++i)
seq[BLOCK*j+1+i] = i + prng() % (BLOCK - i);
}
}
template <typename TYPE>
void forward(TYPE *array)
{
for (int j = 0; j < BLOCKS; ++j) {
if (j < BLOCKS-1)
for (int i = 0; i < BLOCK; ++i)
std::swap(array[BLOCK*j+i], array[BLOCK*seq[BLOCK*j]+i]);
for (int i = 0; i < BLOCK-1; ++i)
std::swap(array[BLOCK*j+i], array[BLOCK*j+seq[BLOCK*j+1+i]]);
}
}
template <typename TYPE>
void reverse(TYPE *array)
{
for (int j = BLOCKS-1; j >= 0; --j) {
for (int i = BLOCK-2; i >= 0; --i)
std::swap(array[BLOCK*j+i], array[BLOCK*j+seq[BLOCK*j+1+i]]);
if (j < BLOCKS-1)
for (int i = 0; i < BLOCK; ++i)
std::swap(array[BLOCK*j+i], array[BLOCK*seq[BLOCK*j]+i]);
}
}
};
template <int SIZE, typename TYPE>
static void BitReversalPermute(TYPE *array)
{