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Memoized powers of two for bitwise ops (all except for NOT).

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Favian Contreras 2014-12-08 12:59:57 -08:00
parent c3fd516671
commit 35052bdac5
1 changed files with 33 additions and 9 deletions
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42
decimal.js
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@ -45,7 +45,10 @@
INT_POW_LIMIT = 3000, // 0 to 5000 INT_POW_LIMIT = 3000, // 0 to 5000
// The natural logarithm of 10 (1025 digits). // The natural logarithm of 10 (1025 digits).
LN10 = '2.3025850929940456840179914546843642076011014886287729760333279009675726096773524802359972050895982983419677840422862486334095254650828067566662873690987816894829072083255546808437998948262331985283935053089653777326288461633662222876982198867465436674744042432743651550489343149393914796194044002221051017141748003688084012647080685567743216228355220114804663715659121373450747856947683463616792101806445070648000277502684916746550586856935673420670581136429224554405758925724208241314695689016758940256776311356919292033376587141660230105703089634572075440370847469940168269282808481184289314848524948644871927809676271275775397027668605952496716674183485704422507197965004714951050492214776567636938662976979522110718264549734772662425709429322582798502585509785265383207606726317164309505995087807523710333101197857547331541421808427543863591778117054309827482385045648019095610299291824318237525357709750539565187697510374970888692180205189339507238539205144634197265287286965110862571492198849978748873771345686209167058'; LN10 = '2.3025850929940456840179914546843642076011014886287729760333279009675726096773524802359972050895982983419677840422862486334095254650828067566662873690987816894829072083255546808437998948262331985283935053089653777326288461633662222876982198867465436674744042432743651550489343149393914796194044002221051017141748003688084012647080685567743216228355220114804663715659121373450747856947683463616792101806445070648000277502684916746550586856935673420670581136429224554405758925724208241314695689016758940256776311356919292033376587141660230105703089634572075440370847469940168269282808481184289314848524948644871927809676271275775397027668605952496716674183485704422507197965004714951050492214776567636938662976979522110718264549734772662425709429322582798502585509785265383207606726317164309505995087807523710333101197857547331541421808427543863591778117054309827482385045648019095610299291824318237525357709750539565187697510374970888692180205189339507238539205144634197265287286965110862571492198849978748873771345686209167058',
// Array to memoize powers of 2
POWERS_OF_TWO = [1];
// Decimal prototype methods // Decimal prototype methods
@ -397,6 +400,9 @@
var twoPowN = null; var twoPowN = null;
if (typeof n === 'object' || !isFinite(n) || +n >= 50) { if (typeof n === 'object' || !isFinite(n) || +n >= 50) {
n = new Decimal(n)['trunc'](); n = new Decimal(n)['trunc']();
if (POWERS_OF_TWO[n['toNumber']()] !== undefined) {
twoPowN = POWERS_OF_TWO[n['toNumber']()];
}
} else { } else {
if (isNaN(parseInt(n))) { if (isNaN(parseInt(n))) {
return new Decimal(NaN); return new Decimal(NaN);
@ -419,7 +425,8 @@
Decimal['precision'] = MAX_DIGITS; Decimal['precision'] = MAX_DIGITS;
if (!twoPowN) { if (!twoPowN) {
twoPowN = new Decimal(2)['pow'](n); twoPowN = new Decimal(2)['pow'](n);
POWERS_OF_TWO[n['toNumber']()] = twoPowN;
} }
var outVal = x['times'](twoPowN); var outVal = x['times'](twoPowN);
@ -1115,15 +1122,20 @@
var Decimal = this['constructor'], var Decimal = this['constructor'],
x = this['trunc'](); x = this['trunc']();
var twoPowN = null; var twoPowN, nNum;
if (typeof n === 'object' || !isFinite(n) || +n >= 50) { if (typeof n === 'object' || !isFinite(n) || +n >= 50) {
n = new Decimal(n)['trunc'](); n = new Decimal(n)['trunc']();
nNum = n['toNumber']();
if (POWERS_OF_TWO[nNum] !== undefined) {
twoPowN = POWERS_OF_TWO[nNum];
}
} else { } else {
if (isNaN(parseInt(n))) { if (isNaN(parseInt(n))) {
return new Decimal(NaN); return new Decimal(NaN);
} }
twoPowN = new Decimal(mathpow(2, n | 0)); nNum = n | 0;
n = new Decimal(n | 0); twoPowN = new Decimal(mathpow(2, nNum));
n = new Decimal(nNum);
} }
// Are both infinity or is shift amount negative or amount is negative and shift is infinite? // Are both infinity or is shift amount negative or amount is negative and shift is infinite?
@ -1141,7 +1153,8 @@
Decimal['precision'] = MAX_DIGITS; Decimal['precision'] = MAX_DIGITS;
if (!twoPowN) { if (!twoPowN) {
twoPowN = new Decimal(2)['pow'](n); twoPowN = new Decimal(2)['pow'](n);
POWERS_OF_TWO[nNum] = twoPowN;
} }
var outVal = x['div'](twoPowN)['floor'](); var outVal = x['div'](twoPowN)['floor']();
@ -2208,19 +2221,30 @@
expFuncVal = func(xSign, ySign) ^ 1, expFuncVal = func(xSign, ySign) ^ 1,
outVal = new Decimal(expFuncVal ? 0 : 1), outVal = new Decimal(expFuncVal ? 0 : 1),
twoPower = Decimal['ONE'], twoPower = Decimal['ONE'],
two = new Decimal(2); two = new Decimal(2)
i = 0;
while (shortLen > 0) { while (shortLen > 0) {
if (func(minBits[--shortLen], maxBits[--longLen]) == expFuncVal) { if (func(minBits[--shortLen], maxBits[--longLen]) == expFuncVal) {
outVal = outVal['plus'](twoPower); outVal = outVal['plus'](twoPower);
} }
twoPower = twoPower['times'](two); if (POWERS_OF_TWO[++i] !== undefined) {
twoPower = POWERS_OF_TWO[i];
} else {
twoPower = twoPower['times'](two);
POWERS_OF_TWO[i] = twoPower;
}
} }
while (longLen > 0) { while (longLen > 0) {
if (func(minSign, maxBits[--longLen]) == expFuncVal) { if (func(minSign, maxBits[--longLen]) == expFuncVal) {
outVal = outVal['plus'](twoPower); outVal = outVal['plus'](twoPower);
} }
twoPower = twoPower['times'](two); if (POWERS_OF_TWO[++i] !== undefined) {
twoPower = POWERS_OF_TWO[i];
} else {
twoPower = twoPower['times'](two);
POWERS_OF_TWO[i] = twoPower;
}
} }
if (expFuncVal == 0) { if (expFuncVal == 0) {
outVal['s'] = -outVal['s']; outVal['s'] = -outVal['s'];