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function x=%lss_inv(a)
// Copyright INRIA
d=a(5);
[m,n]=size(d);
polyn=(type(d)==2);constant=(type(d)==1);
if constant&(m==n) then
minsv=mini(svd(d));rcd=rcond(d);s=poly(0,'s');
end
if constant&(m<>n) then
minsv=mini(svd(d));s=poly(0,'s');
end
if polyn then rcd=0;minsv=0;s=poly(0,varn(d));end
if m==n then
if rcd > 1.d-6 then
x=invsyslin(a)
else
h=systmat(a);
se=rand('seed');
valfa=rand(1,10,'normal')/100;
rand('seed',se);
www=[];
for k=1:10
www=[www,rcond(horner(h,valfa(k)))];end
[w,k1]=maxi(www);alfa=valfa(k1);
x=invrs(a,alfa);
end
elseif m<n then
warning('non square system! --> right inverse')
if minsv > 1.d-6 then
x=invsyslin(a)
else
[stmp,ws]=rowregul(a,0,0);
if mini(svd(stmp(5))) > 1.d-6 then
x=invsyslin(stmp)*ws
else
error(19)
end
end
elseif m>n then
warning('non square system! --> left inverse')
if minsv > 1.d-6 then
x=invsyslin(a)
else
[stmp,ws]=rowregul(a,0,0);
if mini(svd(stmp(5))) > 1.d-6 then
x=invsyslin(stmp)*ws
else
error(19)
end
end
end
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