# FORTRAN77从文件中读入若干数据并用heron迭代公式开方

2020-11-08 01:33:53

1.不限制数据个数,自动计数并打印序号

2.遇到负数时，跳过开方，直接打印并标记

3.遇到0.0,程序停止

Heron迭代方法。

1. 初始化 (X0 = A);(x1 =1/2*{x0+A/ x0});
2. 计算 (Delta_k = |x1 - x0|;
3. (Delta_k < epsilon)，返回(x)，算法结束;
4. (x1 =1/2*{x0+A/ x0});
5. 返回第2步;
``````C
C   heronus1.f
C
C Unlimited number of data, automatic counting and printing serial number
C When negative numbers are encountered,skip square root, print them directly and mark them
C Encountered 0.0, the program stopped

PROGRAM heronus1
EPS=.1 E-4
I=0
OPEN(11,file='fheronus.dat')
I=I+1
IF (A) 1,2,30
1  WRITE(6,100) I,A
100 FORMAT(1X, I6,10X,F10.6,'	NEGATIVE NUMBER')
GO TO 10
2  STOP 'END OF JOB'
30 X0=A
20 X1=.5*(X0+A/X0)
IF (ABS(X1-X0).LT.EPS) GO TO 40
X0=X1
GO TO 20
40 WRITE(6,110) I,A,X1
110 FORMAT(1X, I6,2F10.6)
3  CONTINUE
GO TO 10
END``````

``````\$ cat fheronus.dat
1
2
3
4
5
6
7
8
9
10
11
12
12
13
13
14
16
21
22
13
25
22
13
21
52
32
-23
121
12
0.0
``````

``````\$ f77 heronus1.f
\$ a.out
1  1.000000  1.000000
2  2.000000  1.414214
3  3.000000  1.732051
4  4.000000  2.000000
5  5.000000  2.236068
6  6.000000  2.449490
7  7.000000  2.645751
8  8.000000  2.828427
9  9.000000  3.000000
10 10.000000  3.162278
11 11.000000  3.316625
12 12.000000  3.464102
13 12.000000  3.464102
14 13.000000  3.605551
15 13.000000  3.605551
16 14.000000  3.741657
17 16.000000  4.000000
18 21.000000  4.582576
19 22.000000  4.690416
20 13.000000  3.605551
21 25.000000  5.000000
22 22.000000  4.690416
23 13.000000  3.605551
24 21.000000  4.582576
25 52.000000  7.211102
26 32.000000  5.656854
27          -23.000000	NEGATIVE NUMBER
28121.000000 11.000000
29 12.000000  3.464102
STOP END OF JOB
``````

ubutnu18.04下gfortran-10编译通过(vax780的f77也测试过)

https://my.oschina.net/u/2245781/blog/4707791