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公司項(xiàng)目里面需要做大量的高精度運(yùn)算，剛開始用double類型運(yùn)算，后來(lái)發(fā)現(xiàn)用double類型運(yùn)算后有些值的精確度超過(guò)了理想范圍，就用了BigDecimal來(lái)計(jì)算，現(xiàn)在的問(wèn)題是BigDecimal的運(yùn)算效率比double慢幾十倍，數(shù)據(jù)量大的話，慢的要死。請(qǐng)問(wèn)有沒有好的解決方案？這個(gè)問(wèn)題急需解決。

//相關(guān)性系數(shù)計(jì)算
public BigDecimal getRelativityTool_bydim(RelativityTool u) {
        BigDecimal sim = new BigDecimal("0"); //最后的皮爾遜相關(guān)度系數(shù)

        BigDecimal common_items_len = new BigDecimal(this.rating_map_list.size()); //操作數(shù)的個(gè)數(shù)

        BigDecimal this_sum = new BigDecimal("0"); //第一個(gè)相關(guān)數(shù)的和

        BigDecimal u_sum = new BigDecimal("0"); //第二個(gè)相關(guān)數(shù)的和

        BigDecimal this_sum_sq = new BigDecimal("0"); //第一個(gè)相關(guān)數(shù)的平方和

        BigDecimal u_sum_sq = new BigDecimal("0"); //第二個(gè)相關(guān)數(shù)的平方和

        BigDecimal p_sum = new BigDecimal("0"); //兩個(gè)相關(guān)數(shù)乘積的和

        for (int i = 0; i < this.rating_map_list.size(); i++) {
            BigDecimal this_grade = this.rating_map_list.get(i);
            BigDecimal u_grade = u.rating_map_list.get(i);
            //評(píng)分求和                     //平方和                     //乘積和

            this_sum = this_sum.add(this_grade);
            u_sum = u_sum.add(u_grade);
            this_sum_sq = this_sum_sq.add(this_grade.pow(2));
            u_sum_sq = u_sum_sq.add(u_grade.pow(2));
            p_sum = p_sum.add(this_grade.multiply(u_grade));
        }
        BigDecimal num = common_items_len.multiply(p_sum).subtract(this_sum.multiply(u_sum));
        BigDecimal den = sqrt(common_items_len.multiply(this_sum_sq).subtract(this_sum.pow(2)).multiply(common_items_len.multiply(u_sum_sq).subtract(u_sum.pow(2))));
        if (den.compareTo(new BigDecimal("0")) == 0) {
            sim = new BigDecimal("1");
        } else {
            sim = num.pide(den,5, BigDecimal.ROUND_HALF_UP);
        }
        return sim;
    }
    //大數(shù)字開方
    public static BigDecimal sqrt(BigDecimal x) {
        BigDecimal n1 = BigDecimal.ONE;
        BigDecimal ans = BigDecimal.ZERO;
        while ((n1.multiply(n1).subtract(x)).abs().compareTo(BigDecimal.valueOf(0.001)) == 1) {
            BigDecimal s1 = x.pide(n1, 2000, BigDecimal.ROUND_HALF_UP);
            BigDecimal s2 = n1.add(s1);
            n1 = s2.pide(BigDecimal.valueOf(2), 2000, BigDecimal.ROUND_HALF_UP);

        }
        ans = n1;
        BigDecimal rt = new BigDecimal(ans.toString().split("\\.")[0]);
        return rt;
    }

public void test_sqrt() { BigDecimal x = BigDecimal.valueOf(Long.MAX_VALUE); BigDecimal x0 = BigDecimal.ZERO; BigDecimal x2 = new BigDecimal(2); BigDecimal x1 = new BigDecimal(Math.sqrt(x.doubleValue())); while (!x0.equals(x1)) { x0 = x1; x1 = x.pide(x0, 2000, BigDecimal.ROUND_HALF_UP); x1 = x1.add(x0); x1 = x1.pide(x2, 2000, BigDecimal.ROUND_HALF_UP); } assertEquals(3037000499L, x1.longValue()); }