 http://www.ccl.net/cca/software/SOURCES/FORTRAN/chelpg/new/svd.f.shtml CCL svd.f
```Received: (from mfrancl@localhost) by kelvin.brynmawr.edu (8.6.12/8.6.12) id LAA02519 for srusso@cc; Fri, 19 May 1995 11:05:50 -0400 Date: Fri, 19 May 1995 11:05:50 -0400
From: Francl Michelle M
Message-Id: <199505191505.LAA02519@kelvin.brynmawr.edu> To: srusso
X-UIDL: 800896205.000

cc
cc	a calling routine to do svd's on the chelp matrix
cc
implicit real*8 (a-h,o-z)
logical matu,matv
dimension a(100,100),w(100),u(100,100),v(100,100),rv1(100) dimension cn(100)
data tol/0.0001/
c
ndim=100
matu=.true.
matv=.true.
c
do 100 k=1,nrows
100 continue
c
call svd(ndim,nrows,ncol,a,w,matu,u,matv,v,ierr,rv1) c
write(6,*) 'error status = (0 for normal) ',ierr write(6,*) 'u matrix'
do 200 k=1,nrows
write(6,1000) (u(k,mu),mu=1,nrows)
1000 format(1x,5f10.4)
200 continue
c
write(6,*) 'v matrix'
do 300 k=1,nrows
write(6,1000) (v(k,mu),mu=1,nrows)
300 continue
c
write(6,*) 'singular values'
write(6,1000) (w(mu),mu=1,nrows)
c
c	compute rank estimate
c
irank = nrows
do 400 i=1,nrows
cn(i) = w(i)/w(1)
if (cn(i).lt.tol) irank=irank-1
400 continue
write(6,*) 'condition numbers (inverses)' write(6,1000) (cn(mu),mu=1,nrows)
write(6,*) 'rank = ',irank
c
end
c
cc
cc This version obtained on 1 Jun 84 from (kahaner@nbs-sdc) cc David K. Kahaner
cc Scientific Computing Division
cc National Bureau of Standards
cc Washington DC 20234
cc
cc	WARNING: the calling sequences here differ from those in the book:
cc R. Piessens, E. deDoncker-Kapenga, C. Uberhuber, D. Kahaner cc Quadpack: a Subroutine Package for Automatic Integration cc Springer Verlag, 1983. Series in Computational Mathematics v.1 cc
subroutine svd(nm,m,n,a,w,matu,u,matv,v,ierr,rv1) c
implicit real*8(a-h,o-z)
c
cc	integer i,j,k,l,m,n,ii,i1,kk,k1,ll,l1,mn,nm,its,ierr
cc	double precision a(nm,n),w(n),u(nm,n),v(nm,n),rv1(n)
cc	double precision c,f,g,h,s,x,y,z,tst1,tst2,scale,pythag
dimension a(nm,n),w(n),u(nm,n),v(nm,n),rv1(n) logical matu,matv
c
c	this subroutine is a translation of the algol procedure svd,
c	num. math. 14, 403-420(1970) by golub and reinsch.
c	handbook for auto. comp., vol ii-linear algebra, 134-151(1971).
c
c	this subroutine determines the singular value decomposition
c	t
c	a=usv of a real m by n rectangular matrix. householder
c	bidiagonalization and a variant of the qr algorithm are used.
c
c	on input
c
c	nm must be set to the row dimension of two-dimensional
c	array parameters as declared in the calling program
c	dimension statement. note that nm must be at least
c	as large as the maximum of m and n.
c
c	m is the number of rows of a (and u).
c
c	n is the number of columns of a (and u) and the order of v.
c
c	a contains the rectangular input matrix to be decomposed.
c
c	matu should be set to .true. if the u matrix in the
c	decomposition is desired, and to .false. otherwise.
c
c	matv should be set to .true. if the v matrix in the
c	decomposition is desired, and to .false. otherwise.
c
c	on output
c
c	a is unaltered (unless overwritten by u or v).
c
c	w contains the n (non-negative) singular values of a (the
c	diagonal elements of s). they are unordered. if an
c	error exit is made, the singular values should be correct
c	for indices ierr+1,ierr+2,...,n.
c
c	u contains the matrix u (orthogonal column vectors) of the
c	decomposition if matu has been set to .true. otherwise
c	u is used as a temporary array. u may coincide with a.
c	if an error exit is made, the columns of u corresponding
c	to indices of correct singular values should be correct.
c
c	v contains the matrix v (orthogonal) of the decomposition if
c	matv has been set to .true. otherwise v is not referenced.
c	v may also coincide with a if u is not needed. if an error
c	exit is made, the columns of v corresponding to indices of
c	correct singular values should be correct.
c
c	ierr is set to
c	zero	for normal return,
c	k	if the k-th singular value has not been
c	determined after 30 iterations.
c
c	rv1 is a temporary storage array.
c
c	calls pythag for dsqrt(a*a + b*b) .
c
c	questions and comments should be directed to burton s. garbow,
c	mathematics and computer science div, argonne national laboratory
c
c	this version dated august 1983.
c
c	------------------------------------------------------------------
c
ierr = 0
c
do 100 i = 1, m
c
do 100 j = 1, n
u(i,j) = a(i,j)
100 continue
c	.......... householder reduction to bidiagonal form ..........
g = 0.0d0
scale = 0.0d0
x = 0.0d0
c
do 300 i = 1, n
l = i + 1
rv1(i) = scale * g
g = 0.0d0
s = 0.0d0
scale = 0.0d0
if (i .gt. m) go to 210
c
do 120 k = i, m
120 scale = scale + dabs(u(k,i))
c
if (scale .eq. 0.0d0) go to 210
c
do 130 k = i, m
u(k,i) = u(k,i) / scale
s = s + u(k,i)**2
130 continue
c
f = u(i,i)
g = -dsign(dsqrt(s),f)
h = f * g - s
u(i,i) = f - g
if (i .eq. n) go to 190
c
do 150 j = l, n
s = 0.0d0
c
do 140 k = i, m
140	s = s + u(k,i) * u(k,j)
c
f = s / h
c
do 150 k = i, m
u(k,j) = u(k,j) + f * u(k,i)
150 continue
c
190 do 200 k = i, m
200 u(k,i) = scale * u(k,i)
c
210 w(i) = scale * g
g = 0.0d0
s = 0.0d0
scale = 0.0d0
if (i .gt. m .or. i .eq. n) go to 290
c
do 220 k = l, n
220 scale = scale + dabs(u(i,k))
c
if (scale .eq. 0.0d0) go to 290
c
do 230 k = l, n
u(i,k) = u(i,k) / scale
s = s + u(i,k)**2
230 continue
c
f = u(i,l)
g = -dsign(dsqrt(s),f)
h = f * g - s
u(i,l) = f - g
c
do 240 k = l, n
240 rv1(k) = u(i,k) / h
c
if (i .eq. m) go to 270
c
do 260 j = l, m
s = 0.0d0
c
do 250 k = l, n
250	s = s + u(j,k) * u(i,k)
c
do 260 k = l, n
u(j,k) = u(j,k) + s * rv1(k)
260 continue
c
270 do 280 k = l, n
280 u(i,k) = scale * u(i,k)
c
290 x = dmax1(x,dabs(w(i))+dabs(rv1(i))) 300 continue
c	.......... accumulation of right-hand transformations ..........
if (.not. matv) go to 410
c	.......... for i=n step -1 until 1 do -- ..........
do 400 ii = 1, n
i = n + 1 - ii
if (i .eq. n) go to 390
if (g .eq. 0.0d0) go to 360
c
do 320 j = l, n
c	.......... double division avoids possible underflow ..........
320 v(j,i) = (u(i,j) / u(i,l)) / g
c
do 350 j = l, n
s = 0.0d0
c
do 340 k = l, n
340	s = s + u(i,k) * v(k,j)
c
do 350 k = l, n
v(k,j) = v(k,j) + s * v(k,i)
350 continue
c
360 do 380 j = l, n
v(i,j) = 0.0d0
v(j,i) = 0.0d0
380 continue
c
390 v(i,i) = 1.0d0
g = rv1(i)
l = i
400 continue
c	.......... accumulation of left-hand transformations ..........
410 if (.not. matu) go to 510
c	..........for i=min(m,n) step -1 until 1 do -- ..........
mn = n
if (m .lt. n) mn = m
c
do 500 ii = 1, mn
i = mn + 1 - ii
l = i + 1
g = w(i)
if (i .eq. n) go to 430
c
do 420 j = l, n
420 u(i,j) = 0.0d0
c
430 if (g .eq. 0.0d0) go to 475
if (i .eq. mn) go to 460
c
do 450 j = l, n
s = 0.0d0
c
do 440 k = l, m
440	s = s + u(k,i) * u(k,j)
c	.......... double division avoids possible underflow ..........
f = (s / u(i,i)) / g
c
do 450 k = i, m
u(k,j) = u(k,j) + f * u(k,i)
450 continue
c
460 do 470 j = i, m
470 u(j,i) = u(j,i) / g
c
go to 490
c
475 do 480 j = i, m
480 u(j,i) = 0.0d0
c
490 u(i,i) = u(i,i) + 1.0d0
500 continue
c	.......... diagonalization of the bidiagonal form ..........
510 tst1 = x
c	.......... for k=n step -1 until 1 do -- ..........
do 700 kk = 1, n
k1 = n - kk
k = k1 + 1
its = 0
c	.......... test for splitting.
c	for l=k step -1 until 1 do -- ..........
520 do 530 ll = 1, k
l1 = k - ll
l = l1 + 1
tst2 = tst1 + dabs(rv1(l))
if (tst2 .eq. tst1) go to 565
c	.......... rv1(1) is always zero, so there is no exit
c	through the bottom of the loop ..........
tst2 = tst1 + dabs(w(l1))
if (tst2 .eq. tst1) go to 540
530 continue
c	.......... cancellation of rv1(l) if l greater than 1 ..........
540 c = 0.0d0
s = 1.0d0
c
do 560 i = l, k
f = s * rv1(i)
rv1(i) = c * rv1(i)
tst2 = tst1 + dabs(f)
if (tst2 .eq. tst1) go to 565
g = w(i)
h = pythag(f,g)
w(i) = h
c = g / h
s = -f / h
if (.not. matu) go to 560
c
do 550 j = 1, m
y = u(j,l1)
z = u(j,i)
u(j,l1) = y * c + z * s
u(j,i) = -y * s + z * c
550	continue
c
560 continue
c	.......... test for convergence ..........
565 z = w(k)
if (l .eq. k) go to 650
c	.......... shift from bottom 2 by 2 minor ..........
if (its .eq. 30) go to 1000
its = its + 1
x = w(l)
y = w(k1)
g = rv1(k1)
h = rv1(k)
f = 0.5d0 * (((g + z) / h) * ((g - z) / y) + y / h - h / y) g = pythag(f,1.0d0)
f = x - (z / x) * z + (h / x) * (y / (f + dsign(g,f)) - h) c	.......... next qr transformation ..........
c = 1.0d0
s = 1.0d0
c
do 600 i1 = l, k1
i = i1 + 1
g = rv1(i)
y = w(i)
h = s * g
g = c * g
z = pythag(f,h)
rv1(i1) = z
c = f / z
s = h / z
f = x * c + g * s
g = -x * s + g * c
h = y * s
y = y * c
if (.not. matv) go to 575
c
do 570 j = 1, n
x = v(j,i1)
z = v(j,i)
v(j,i1) = x * c + z * s
v(j,i) = -x * s + z * c
570	continue
c
575	z = pythag(f,h)
w(i1) = z
c	.......... rotation can be arbitrary if z is zero ..........
if (z .eq. 0.0d0) go to 580
c = f / z
s = h / z
580	f = c * g + s * y
x = -s * g + c * y
if (.not. matu) go to 600
c
do 590 j = 1, m
y = u(j,i1)
z = u(j,i)
u(j,i1) = y * c + z * s
u(j,i) = -y * s + z * c
590	continue
c
600 continue
c
rv1(l) = 0.0d0
rv1(k) = f
w(k) = x
go to 520
c	.......... convergence ..........
650 if (z .ge. 0.0d0) go to 700
c	.......... w(k) is made non-negative ..........
w(k) = -z
if (.not. matv) go to 700
c
do 690 j = 1, n
690 v(j,k) = -v(j,k)
c
700 continue
c
go to 1001
c	.......... set error -- no convergence to a
c	singular value after 30 iterations ..........
1000 ierr = k
1001 return
end
double precision function pythag(a,b)
double precision a,b
c
c	finds dsqrt(a**2+b**2) without overflow or destructive underflow
c
double precision p,r,s,t,u
p = dmax1(dabs(a),dabs(b))
if (p .eq. 0.0d0) go to 20
r = (dmin1(dabs(a),dabs(b))/p)**2
10 continue
t = 4.0d0 + r
if (t .eq. 4.0d0) go to 20
s = r/t
u = 1.0d0 + 2.0d0*s
p = u*p
r = (s/u)**2 * r
go to 10
20 pythag = p
return
end

```
 Modified: Mon May 22 16:00:00 1995 GMT Page accessed 10737 times since Sat Apr 17 22:01:34 1999 GMT