File: drotg.f

package info (click to toggle)
insighttoolkit 3.6.0-3
  • links: PTS
  • area: main
  • in suites: lenny
  • size: 94,956 kB
  • ctags: 74,981
  • sloc: cpp: 355,621; ansic: 195,070; fortran: 28,713; python: 3,802; tcl: 1,996; sh: 1,175; java: 583; makefile: 415; csh: 184; perl: 175
file content (27 lines) | stat: -rw-r--r-- 674 bytes parent folder | download | duplicates (58) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
 
      subroutine drotg(da,db,c,s)
c
c     construct givens plane rotation.
c     jack dongarra, linpack, 3/11/78.
c
      double precision da,db,c,s,roe,scale,r,z
c
      roe = db
      if( dabs(da) .gt. dabs(db) ) roe = da
      scale = dabs(da) + dabs(db)
      if( scale .ne. 0.0d0 ) go to 10
         c = 1.0d0
         s = 0.0d0
         r = 0.0d0
         z = 0.0d0
         go to 20
   10 r = scale*dsqrt((da/scale)**2 + (db/scale)**2)
      r = dsign(1.0d0,roe)*r
      c = da/r
      s = db/r
      z = 1.0d0
      if( dabs(da) .gt. dabs(db) ) z = s
      if( dabs(db) .ge. dabs(da) .and. c .ne. 0.0d0 ) z = 1.0d0/c
   20 da = r
      db = z
      return
      end