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Add support for signed modular inversion.

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This commit is contained in:
Adam Wick
2018-12-30 17:14:11 -08:00
parent a6a82773d3
commit 130a87ef43
3 changed files with 105 additions and 16 deletions
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72
src/signed/modinv.rs
View File

@@ -6,6 +6,33 @@ pub trait ModInv: Sized {
fn modinv(&self, phi: &Self) -> Option<Self>;
}
macro_rules! smodinv_impls {
($name: ident, $bigger: ident) => {
impl ModInv for $name {
fn modinv(&self, phi: &$name) -> Option<$name>
{
let (_, mut b, g) = phi.egcd(&self);
if g != $bigger::from(1u64) {
return None;
}
let bigphi = $bigger::from(phi);
while b.is_negative() {
b += &bigphi;
}
if b > bigphi {
b -= &bigphi;
}
Some($name::from(b))
}
}
}
}
macro_rules! modinv_impls {
($name: ident, $sname: ident, $uname: ident) => {
impl ModInv for $name {
@@ -17,8 +44,14 @@ macro_rules! modinv_impls {
return None;
}
let sphi = $sname::from($uname::from(phi));
while b.is_negative() {
b += $sname::from($uname::from(phi));
b += &sphi;
}
if b > sphi {
b -= &sphi;
}
Some($name::from($uname::from(b)))
@@ -54,6 +87,43 @@ macro_rules! generate_modinv_tests {
let b = $tname::from_bytes(bbytes);
let c = $tname::from_bytes(cbytes);
match a.modinv(&b) {
None => assert!(false),
Some(myc) => {
assert_eq!(c, myc);
}
}
});
};
}
#[cfg(test)]
macro_rules! generate_smodinv_tests {
($sname: ident, $tname: ident, $mname: ident) => {
#[test]
fn $mname() {
generate_smodinv_tests!(body $sname, $tname, $mname);
}
};
(ignore $sname: ident, $tname: ident, $mname: ident) => {
#[test]
#[ignore]
fn $mname() {
generate_smodinv_tests!(body $sname, $tname, $mname);
}
};
(body $sname: ident, $tname: ident, $mname: ident) => {
let fname = build_test_path("modinv", stringify!($sname));
run_test(fname.to_string(), 3, |case| {
let (nega, abytes) = case.get("a").unwrap();
let (negb, bbytes) = case.get("b").unwrap();
let (negc, cbytes) = case.get("c").unwrap();
assert!(!negb && !negc);
let a = $sname::new(*nega, $tname::from_bytes(abytes));
let b = $sname::new(false, $tname::from_bytes(bbytes));
let c = $sname::new(false, $tname::from_bytes(cbytes));
match a.modinv(&b) {
None => assert!(false),
Some(myc) => {

28
test-generator/Invocs.hs
View File

@@ -101,7 +101,8 @@ main = do
SignedSub -> hPutStrLn hndl ("subtraction_impls!(I" ++ show size ++ ", I" ++ show (size + 64) ++ ", U" ++ show (size + 64) ++ ");")
SignedMul -> hPutStrLn hndl ("mul_impls!(I" ++ show size ++ ", I" ++ show (size * 2) ++ ");")
SignedDiv -> hPutStrLn hndl ("div_impls!(I" ++ show size ++ ", U" ++ show size ++ ");")
EGCD -> hPutStrLn hndl ("egcd_impls!(I" ++ show (size + 64) ++ ", U" ++ show size ++ ", I" ++ show size ++ ");")
SignedModInv -> hPutStrLn hndl ("smodinv_impls!(I" ++ show size ++ ", I" ++ show (size + 64) ++ ");")
EGCD -> hPutStrLn hndl ("egcd_impls!(I" ++ show (size + 64) ++ ", U" ++ show size ++ ", I" ++ show size ++ ", I" ++ show ((size + 64) * 2) ++ ");")
ModDiv -> hPutStrLn hndl ("moddiv_impls!(I" ++ show size ++ ", I" ++ show (size * 2) ++ ");")
ModInv -> hPutStrLn hndl ("modinv_impls!(U" ++ show size ++ ", I" ++ show (size + 64) ++ ", U" ++ show (size + 64) ++ ");")
SigConvert v -> hPutStrLn hndl ("conversion_impls!(I" ++ show size ++ ", U" ++ show size ++ ", I" ++ show v ++ ", U" ++ show v ++ ");")
@@ -109,16 +110,17 @@ main = do
hPutStrLn hndl ""
hPutStrLn hndl "\n#[cfg(test)]"
hPutStrLn hndl "mod tests {"
generateSigTestBlock hndl "sigadd" SignedAdd True 16384 [(+ 64)] [(+ 64)]
generateSigTestBlock hndl "sigsub" SignedSub True 16384 [(+ 64)] [(+ 64)]
generateSigTestBlock hndl "signed" SignedBase True 90000 [] []
generateSigTestBlock hndl "sigconversion" SignedBase False 90000 [] []
generateSigTestBlock hndl "sigcmp" SignedCmp True 90000 [] []
generateSigTestBlock hndl "sigmul" SignedMul True 9000 [(* 2)] [(* 2)]
generateSigTestBlock hndl "sigdiv" SignedDiv True 2049 [] []
generateSigTestBlock hndl "sigshiftl" SignedShift True 16384 [] []
generateSigTestBlock hndl "sigshiftr" SignedShift True 16384 [] []
generateSigTestBlock hndl "egcd" EGCD True 1024 [(+ 64)] [(+ 64)]
generateSigTestBlock hndl "moddiv" ModDiv True 2048 [] []
generateSigTestBlock hndl "modinv" ModInv True 2048 [] []
generateSigTestBlock hndl "sigadd" SignedAdd True 16384 [(+ 64)] [(+ 64)]
generateSigTestBlock hndl "sigsub" SignedSub True 16384 [(+ 64)] [(+ 64)]
generateSigTestBlock hndl "signed" SignedBase True 90000 [] []
generateSigTestBlock hndl "sigconversion" SignedBase False 90000 [] []
generateSigTestBlock hndl "sigcmp" SignedCmp True 90000 [] []
generateSigTestBlock hndl "sigmul" SignedMul True 9000 [(* 2)] [(* 2)]
generateSigTestBlock hndl "sigdiv" SignedDiv True 2049 [] []
generateSigTestBlock hndl "sigshiftl" SignedShift True 16384 [] []
generateSigTestBlock hndl "sigshiftr" SignedShift True 16384 [] []
generateSigTestBlock hndl "egcd" EGCD True 1024 [(+ 64)] [(+ 64)]
generateSigTestBlock hndl "moddiv" ModDiv True 2048 [] []
generateSigTestBlock hndl "modinv" ModInv True 2048 [] []
generateSigTestBlock hndl "smodinv" SignedModInv True 2048 [] []
hPutStrLn hndl "}"

21
test-generator/Tests.hs
View File

@@ -309,5 +309,22 @@ modinvTest size memoryIn =
("c", showX c)]
in if c == 0
then attempt memory2
else assert ((c < b) && ((a * c) `mod` b == 1)) (res, c, memory2)
in attempt memoryIn
else assert (c < b) $
assert ((a * c) `mod` b == 1) $
(res, c, memory2)
in attempt memoryIn
smodinvTest :: Test
smodinvTest size memoryIn =
let attempt memory0 =
let (a, memory1) = genSign (generateNum memory0 "a" size)
(b, memory2) = generateNum memory1 "b" size
c = recipModInteger a b
res = Map.fromList [("a", showX a), ("b", showX b),
("c", showX c)]
in if c == 0
then attempt memory2
else assert (c < b) $
assert ((a * c) `mod` b == 1) $
(res, c, memory2)
in attempt memoryIn