/[lmdze]/trunk/Sources/bibio/tanh_cautious.f
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Annotation of /trunk/Sources/bibio/tanh_cautious.f

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Revision 144 - (hide annotations)
Wed Jun 10 16:46:46 2015 UTC (8 years, 11 months ago) by guez
File size: 766 byte(s) 
In procedure fxhyp, the convoluted computation of tanh(fa/fb) occurred
three times. Extracted it into a function. Also, the computation of
xmoy and fxm was repeated. So stored the values in arrays instead.

In procedure fxhyp, in the computation of fhyp, there were tests
xtild(i) == 0. and xtild(i) == pi_d. No use to do these tests at each
iteration. We now they are true for i == nmax and i == 2 * nmax,
respectively, and we know they are false for other values of
"i". Similarly, in the computations of ffdx and xxpr, there were the
tests xmoy == 0. and xmoy == pi_d, these could not be true.

Moved files from bibio to dyn3d, following LMDZ.
1 guez 144 module tanh_cautious_m
2    
3     implicit none
4    
5     contains
6    
7     elemental double precision function tanh_cautious(fa, fb)
8    
9     ! Compute tanh(fa / fb) with caution.
10    
11     double precision, intent(in):: fa, fb
12    
13     !-------------------------------------------------------------
14    
15     IF (200d0 * fb < - fa) THEN
16     tanh_cautious = - 1d0
17     ELSE IF (200d0 * fb < fa) THEN
18     tanh_cautious = 1d0
19     ELSE
20     IF (ABS(fa) < 1d-13 .AND. ABS(fb) < 1d-13) THEN
21     IF (200d0 * fb + fa < 1d-10) THEN
22     tanh_cautious = - 1d0
23     ELSE IF (200d0 * fb - fa < 1d-10) THEN
24     tanh_cautious = 1d0
25     END IF
26     ELSE
27     tanh_cautious = TANH(fa / fb)
28     END IF
29     END IF
30    
31     end function tanh_cautious
32    
33     end module tanh_cautious_m
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