d44457fc32
* bump snarkvm rev * update default gitignore * impl leo execute * bump snarkvm 0.14.5 * modify examples wip * update run.sh examples * impl env file * clippy warning * fix auction example * fix auction example env * generate new private key for new env - tests failing due to env not found err * commit error changes * Fix tests; clippy * Get examples working * leo build checks that build dir is well formed; clippy * Clean up * Update examples/README.md Co-authored-by: d0cd <pranavsaig@gmail.com> Signed-off-by: Collin Chin <16715212+collinc97@users.noreply.github.com> * do not commit .avm files * use snarkvm commands --------- Signed-off-by: Collin Chin <16715212+collinc97@users.noreply.github.com> Co-authored-by: Pranav Gaddamadugu <pranav@aleo.org> Co-authored-by: d0cd <pranavsaig@gmail.com> |
||
|---|---|---|
| .. | ||
| build | ||
| inputs | ||
| src | ||
| .env | ||
| .gitignore | ||
| program.json | ||
| README.md | ||
src/ntzdebruijn.leo
Build Guide
To compile and run this Leo program, run:
leo run
The Algorithm
This algorithm is detailed in "Hacker's Delight, 2nd edition" by Henry S. Warren, section 5-4, figure 5-26. Here is a summary.
After handling the all-zeros case,
we isolate the rightmost 1 bit in the 32-bit input by
using the C idiom x & (-x). In Leo, the -x is
written as 0u32.sub_wrapped(x).
A constant was discovered with the property that when it was multiplied
by 1, 2, 4, ... 2**31, the 32 values all had different high 5-bit patterns.
This constant is 0x04D7651F.
In the algorithm, the 5 high bits are used as an index into the table
{0, 1, 2, 24, 3, 19, ...}. The table's values were chosen so that
they gave the correct number of trailing zeros for the inputs.
For example, if the isolated bit has 4 trailing zeros, the number is 2**4.
The high 5 bits of 2**4 * 0x04D7651F are 01001 which is 9. The table
value at index 9 is therefore 4.
This algorithm was proposed by Danny Dubé in the comp.compression.research newsgroup: https://groups.google.com/g/comp.compression.research/c/x0NaZ3CJ6O4/m/PfGuchA7o60J
A description of de Bruijn cycles and their use for bit indexing can be seen here: http://supertech.csail.mit.edu/papers/debruijn.pdf