void
mulint ( lrs_mp a, lrs_mp b, lrs_mp c ) /* multiply two integers a*b --> c */
/***Handbook of Algorithms and Data Structures, p239 ***/
{
long nlength, i, j, la, lb;
/*** b and c may coincide ***/
la = length ( a );
lb = length ( b );
nlength = la + lb - 2;
if ( nlength > lrs_digits )
digits_overflow();
for ( i = 0; i < la - 2; i++ )
c[lb + i] = 0;
for ( i = lb - 1; i > 0; i-- ) {
for ( j = 2; j < la; j++ )
if ( ( c[i + j - 1] += b[i] * a[j] ) >
MAXD - ( BASE - 1 ) * ( BASE - 1 ) - MAXD / BASE ) {
c[i + j - 1] -= ( MAXD / BASE ) * BASE;
c[i + j] += MAXD / BASE;
}
c[i] = b[i] * a[1];
}
storelength ( c, nlength );
storesign ( c, sign ( a ) == sign ( b ) ? POS : NEG );
normalize ( c );
}
void
linint ( lrs_mp a, long ka, lrs_mp b, long kb ) /*compute a*ka+b*kb --> a */
/***Handbook of Algorithms and Data Structures P.239 ***/
{
long i, la, lb;
la = length ( a );
lb = length ( b );
for ( i = 1; i < la; i++ )
a[i] *= ka;
if ( sign ( a ) != sign ( b ) )
kb = ( -kb );
if ( lb > la ) {
storelength ( a, lb );
for ( i = la; i < lb; i++ )
a[i] = 0;
}
for ( i = 1; i < lb; i++ )
a[i] += kb * b[i];
normalize ( a );
}
void
normalize ( lrs_mp a ) {
long cy, i, la;
la = length ( a );
start:
cy = 0;
for ( i = 1; i < la; i++ ) {
cy = ( a[i] += cy ) / BASE;
a[i] -= cy * BASE;
if ( a[i] < 0 ) {
a[i] += BASE;
cy--;
}
}
while ( cy > 0 ) {
a[i++] = cy % BASE;
cy /= BASE;
}
if ( cy < 0 ) {
a[la - 1] += cy * BASE;
for ( i = 1; i < la; i++ )
a[i] = ( -a[i] );
storesign ( a, sign ( a ) == POS ? NEG : POS );
goto start;
}
while ( a[i - 1] == 0 && i > 2 )
i--;
if ( i > lrs_record_digits ) {
if ( ( lrs_record_digits = i ) > lrs_digits )
digits_overflow();
};
storelength ( a, i );
if ( i == 2 && a[1] == 0 )
storesign ( a, POS );
} /* end of normalize */
void
itomp (long in, lrs_mp a)
/* convert integer i to multiple precision with base BASE */
{
long i;
a[0] = 2; /* initialize to zero */
for (i = 1; i < lrs_digits; i++)
a[i] = 0;
if (in < 0)
{
storesign (a, NEG);
in = in * (-1);
}
i = 0;
while (in != 0)
{
i++;
a[i] = in - BASE * (in / BASE);
in = in / BASE;
storelength (a, i + 1);
}
} /* end of itomp */
void
gcd ( lrs_mp u, lrs_mp v ) /*returns u=gcd(u,v) destroying v */
/*Euclid's algorithm. Knuth, II, p.320
modified to avoid copies r=u,u=v,v=r
Switches to single precision when possible for greater speed */
{
lrs_mp r;
unsigned long ul, vl;
long i;
static unsigned long maxspval = MAXD; /* Max value for the last digit to guarantee */
/* fitting into a single long integer. */
static long maxsplen; /* Maximum digits for a number that will fit */
/* into a single long integer. */
static long firstime = TRUE;
if ( firstime ) { /* initialize constants */
for ( maxsplen = 2; maxspval >= BASE; maxsplen++ )
maxspval /= BASE;
firstime = FALSE;
}
if ( greater ( v, u ) )
goto bigv;
bigu:
if ( zero ( v ) )
return;
if ( ( i = length ( u ) ) < maxsplen || ( i == maxsplen && u[maxsplen - 1] < maxspval ) )
goto quickfinish;
divint ( u, v, r );
normalize ( u );
bigv:
if ( zero ( u ) ) {
copy ( u, v );
return;
}
if ( ( i = length ( v ) ) < maxsplen || ( i == maxsplen && v[maxsplen - 1] < maxspval ) )
goto quickfinish;
divint ( v, u, r );
normalize ( v );
goto bigu;
/* Base 10000 only at the moment */
/* when u and v are small enough, transfer to single precision integers */
/* and finish with euclid's algorithm, then transfer back to lrs_mp */
quickfinish:
ul = vl = 0;
for ( i = length ( u ) - 1; i > 0; i-- )
ul = BASE * ul + u[i];
for ( i = length ( v ) - 1; i > 0; i-- )
vl = BASE * vl + v[i];
if ( ul > vl )
goto qv;
qu:
if ( !vl ) {
for ( i = 1; ul; i++ ) {
u[i] = ul % BASE;
ul = ul / BASE;
}
storelength ( u, i );
return;
}
ul %= vl;
qv:
if ( !ul ) {
for ( i = 1; vl; i++ ) {
u[i] = vl % BASE;
vl = vl / BASE;
}
storelength ( u, i );
return;
}
vl %= ul;
goto qu;
}
void
divint ( lrs_mp a, lrs_mp b, lrs_mp c ) { /* c=a/b, a contains remainder on return */
long cy, la, lb, lc, d1, s, t, sig;
long i, j, qh;
/* figure out and save sign, do everything with positive numbers */
sig = sign ( a ) * sign ( b );
la = length ( a );
lb = length ( b );
lc = la - lb + 2;
if ( la < lb ) {
storelength ( c, TWO );
storesign ( c, POS );
c[1] = 0;
normalize ( c );
return;
}
for ( i = 1; i < lc; i++ )
c[i] = 0;
storelength ( c, lc );
storesign ( c, ( sign ( a ) == sign ( b ) ) ? POS : NEG );
/******************************/
/* division by a single word: */
/* do it directly */
/******************************/
if ( lb == 2 ) {
cy = 0;
t = b[1];
for ( i = la - 1; i > 0; i-- ) {
cy = cy * BASE + a[i];
a[i] = 0;
cy -= ( c[i] = cy / t ) * t;
}
a[1] = cy;
storesign ( a, ( cy == 0 ) ? POS : sign ( a ) );
storelength ( a, TWO );
/* set sign of c to sig (**mod**) */
storesign ( c, sig );
normalize ( c );
return;
} else {
/* mp's are actually DIGITS+1 in length, so if length of a or b = */
/* DIGITS, there will still be room after normalization. */
/****************************************************/
/* Step D1 - normalize numbers so b > floor(BASE/2) */
d1 = BASE / ( b[lb - 1] + 1 );
if ( d1 > 1 ) {
cy = 0;
for ( i = 1; i < la; i++ ) {
cy = ( a[i] = a[i] * d1 + cy ) / BASE;
a[i] %= BASE;
}
a[i] = cy;
cy = 0;
for ( i = 1; i < lb; i++ ) {
cy = ( b[i] = b[i] * d1 + cy ) / BASE;
b[i] %= BASE;
}
b[i] = cy;
} else {
a[la] = 0; /* if la or lb = DIGITS this won't work */
b[lb] = 0;
}
/*********************************************/
/* Steps D2 & D7 - start and end of the loop */
for ( j = 0; j <= la - lb; j++ ) {
/*************************************/
/* Step D3 - determine trial divisor */
if ( a[la - j] == b[lb - 1] )
qh = BASE - 1;
else {
s = ( a[la - j] * BASE + a[la - j - 1] );
qh = s / b[lb - 1];
while ( qh * b[lb - 2] > ( s - qh * b[lb - 1] ) * BASE + a[la - j - 2] )
qh--;
}
/*******************************************************/
/* Step D4 - divide through using qh as quotient digit */
cy = 0;
for ( i = 1; i <= lb; i++ ) {
s = qh * b[i] + cy;
a[la - j - lb + i] -= s % BASE;
cy = s / BASE;
if ( a[la - j - lb + i] < 0 ) {
a[la - j - lb + i] += BASE;
cy++;
}
}
/*****************************************************/
/* Step D6 - adjust previous step if qh is 1 too big */
if ( cy ) {
qh--;
cy = 0;
for ( i = 1; i <= lb; i++ ) { /* add a back in */
a[la - j - lb + i] += b[i] + cy;
cy = a[la - j - lb + i] / BASE;
a[la - j - lb + i] %= BASE;
}
}
/***********************************************************************/
/* Step D5 - write final value of qh. Saves calculating array indices */
/* to do it here instead of before D6 */
c[la - lb - j + 1] = qh;
}
/**********************************************************************/
/* Step D8 - unnormalize a and b to get correct remainder and divisor */
for ( i = lc; c[i - 1] == 0 && i > 2; i-- ); /* strip excess 0's from quotient */
storelength ( c, i );
if ( i == 2 && c[1] == 0 )
storesign ( c, POS );
cy = 0;
for ( i = lb - 1; i >= 1; i-- ) {
cy = ( a[i] += cy * BASE ) % d1;
a[i] /= d1;
}
for ( i = la; a[i - 1] == 0 && i > 2; i-- ); /* strip excess 0's from quotient */
storelength ( a, i );
if ( i == 2 && a[1] == 0 )
storesign ( a, POS );
if ( cy )
fprintf ( lrs_ofp, "divide error" );
for ( i = lb - 1; i >= 1; i-- ) {
cy = ( b[i] += cy * BASE ) % d1;
b[i] /= d1;
}
}
}
