subroutine y12mbe(n, z, a, snr, nn, rnr, nn1, ha, iha, aflag,
1 iflag,ifail)
c
c
c the non-zero elements of a sparse matrix a are prepared in order to
c solve the system ax=b by use of sparse matrix technique/
c
c
implicit real(a-b,g,p,t-y),integer(c,f,h-n,r-s,z)
real a(nn), aflag(8)
integer snr(nn), rnr(nn1), ha(iha,11), iflag(10)
mode=iflag(4)
ifail=0
if(n.lt.2)ifail=12
if(z.le.0)ifail=13
if(nn.lt.2*z)ifail=5
if(nn1.lt.z)ifail=6
if(ifail.eq.0.and.n.gt.z)ifail=14
if(iha.lt.n)ifail=15
if(mode.lt.0)ifail=16
if(mode.gt.2)ifail=16
if(ifail.ne.0) go to 22
gt1=0.0
do 10 i=1,n
ha(i,2)=0
ha(i,3)=0
10 ha(i,6)=0
c
c find the number of the non-zero elements in each row and column;move
c the non-zero elements in the end of the arrays a and snr;find the
c largest non-zero element in a(in absolute value).
c
do 20 i=1,z
t=abs(a(i))
l3=rnr(i)
l4=snr(i)
if(l4.gt.n.or.l4.lt.1)ifail=24
if(l3.gt.n.or.l3.lt.1)ifail=25
ha(l3,3)=ha(l3,3)+1
ha(l4,6)=ha(l4,6)+1
if(t.gt.gt1)gt1=t
a(z+i)=a(i)
20 snr(z+i)=snr(i)
if(ifail.gt.0)go to 22
c
c store the information of the row starts(in ha(i,1))and of the column
c starts(in ha(i,4)).
c
l1=1
l2=1
do 40 i=1,n
l3=ha(i,3)
l4=ha(i,6)
if(l3.gt.0)go to 21
ifail=17
go to 22
21 if(l4.gt.0)go to 23
ifail=18
go to 22
23 if(mode.eq.2)go to 30
ha(i,9)=l3
ha(i,10)=l4
ha(i,11)=0
ha(l3,2)=ha(l3,2)+1
ha(i,5)=l3
30 ha(i,1)=l1
ha(i,4)=l2
l1=l1+l3
l2=l2+l4
ha(i,3)=0
40 ha(i,6)=0
c
c store the non-zero elements of matrix a(ordered in rows) in the
c first z locations of the array a.do the same for their column numbers
c
do 50 i=1,z
l1=z+i
l3=rnr(i)
l2=ha(l3,1)+ha(l3,3)
a(l2)=a(l1)
snr(l2)=snr(l1)
50 ha(l3,3)=ha(l3,3)+1
c
c store the row numbers of the non-zero elements ordered by columns in
c the first z locations of the array rnr. store information about row
c ends(in ha(i,3)).
c
l4=1
do 70 i=1,n
if(mode.eq.2)go to 60
if(ha(i,2).eq.0)go to 60
ha(i,11)=l4
l4=l4+ha(i,2)
ha(i,2)=ha(i,11)
60 ha(i,3)=ha(i,1)+ha(i,3)-1
l1=ha(i,1)
l2=ha(i,3)
do 70 j=l1,l2
l3=snr(j)
r=ha(l3,6)
index=ha(l3,4)+r
rnr(index)=i
if(r.eq.0)go to 70
if(j.eq.l1)go to 70
if(rnr(index-1).ne.i)go to 70
ifail=11
go to 22
70 ha(l3,6)=r+1
do 90 i=1,n
if(mode.eq.2)go to 80
l3=ha(i,5)
l5=ha(l3,2)
ha(l5,8)=i
ha(i,7)=l5
ha(l3,2)=ha(l3,2)+1
80 continue
90 ha(i,6)=ha(i,4)+ha(i,6)-1
aflag(6)=gt1
iflag(6)=0
iflag(7)=0
iflag(8)=z
iflag(1) = -1
end
.
