70 lines
1.6 KiB
JavaScript
70 lines
1.6 KiB
JavaScript
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// https://github.com/python/cpython/blob/a74eea238f5baba15797e2e8b570d153bc8690a7/Modules/mathmodule.c#L1423
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export class Adder {
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constructor() {
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this._partials = new Float64Array(32);
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this._n = 0;
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}
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add(x) {
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const p = this._partials;
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let i = 0;
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for (let j = 0; j < this._n && j < 32; j++) {
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const y = p[j],
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hi = x + y,
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lo = Math.abs(x) < Math.abs(y) ? x - (hi - y) : y - (hi - x);
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if (lo) p[i++] = lo;
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x = hi;
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}
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p[i] = x;
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this._n = i + 1;
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return this;
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}
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valueOf() {
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const p = this._partials;
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let n = this._n, x, y, lo, hi = 0;
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if (n > 0) {
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hi = p[--n];
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while (n > 0) {
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x = hi;
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y = p[--n];
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hi = x + y;
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lo = y - (hi - x);
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if (lo) break;
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}
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if (n > 0 && ((lo < 0 && p[n - 1] < 0) || (lo > 0 && p[n - 1] > 0))) {
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y = lo * 2;
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x = hi + y;
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if (y == x - hi) hi = x;
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}
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}
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return hi;
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}
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}
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export function fsum(values, valueof) {
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const adder = new Adder();
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if (valueof === undefined) {
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for (let value of values) {
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if (value = +value) {
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adder.add(value);
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}
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}
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} else {
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let index = -1;
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for (let value of values) {
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if (value = +valueof(value, ++index, values)) {
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adder.add(value);
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}
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}
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}
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return +adder;
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}
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export function fcumsum(values, valueof) {
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const adder = new Adder();
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let index = -1;
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return Float64Array.from(values, valueof === undefined
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? v => adder.add(+v || 0)
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: v => adder.add(+valueof(v, ++index, values) || 0)
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);
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}
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