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13
output err=abs(norm(X'-P)); relerr=err/(norm(X)+eps);P=X'; X(j)=(B(j)-A(j,j-1)*X(j-1)'-A(j,j+1)*P(j+1))/A(j,j) X(N)=(B(N)-A(N,N-1)*(X(N-1))')/A(N,N) X(1)=(B(1)-A(1,2)*P(2))/A(1,1) j=1 k=k+1 k>max1 Y N=length(B); k=1 start InputA,B,P,delta,max1 N j=j+1 j>N Y N Y j==1 Y j==N N N N err P109.7 Ëã·¨£º £¨1£©ÊäÈëA,B£¬Áî[N N]=size(A);X=zeros(N,1);C=zeros(1,N+1);Aug=[A B]; p=1¡£ £¨2£©ÅжÏp>N-1ÊÇ·ñ³ÉÁ¢£¬Èô²»³ÉÁ¢£¬Êä³ö½á¹û£»Èô³ÉÁ¢£¬ [Y,j]=max(abs(Aug(p:N,p))); C=Aug(p,:);Aug(p,:)=Aug(j+p-1,:);Aug(j+p-1,:)=C; £¨3£©ÅÐ¶Ï Aug(p,p)==0ÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬Êä³ö½á¹û£»Èô²»³ÉÁ¢£¬Ö´Ðв½Ö裨4£©¡£ £¨4£© Áîk=p+1£¬ÅжÏk>NÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬p=p+1,·µ»Ø²½Öè(2);Èô²»³ÉÁ¢£¬m=Aug(k,p)/Aug(p,p); Aug(k,p:N+1)=Aug(k,p:N+1)-m*Aug(p,p:N+1)£¬k=k+1,·µ»Ø²½Ö裨4£©¡£ £¨5£©X=backsub(Aug(1:N,1:N),Aug(1:N,N+1))£¬Êä³ö½á¹û¡£ ¡¶ÊýÖµ¼ÆËã·½·¨¡·ÊµÑ鱨¸æ 15 end output X=backsub(Aug(1:N,1:N),Aug(1:N,N+1)) m=Aug(k,p)/Aug(p,p); N Aug(k,p:N+1)=Aug(k,p:N+1)-m*Aug(p,p:N+1) k=p+1 Aug(p,p)==0 p=p+1 start [N,N]=size(A);X=zeros(N,1);C=zeros(1,N+1);Aug=[A B]; p=1 p>N-1 Y N [Y,j]=max(abs(Aug(p:N,p))); C=Aug(p,:);Aug(p,:)=Aug(j+p-1,:);Aug(j+p-1,:)=C; Y N Y k>N k=k+1 ¡¶ÊýÖµ¼ÆËã·½·¨¡·ÊµÑ鱨¸æ 16 ?1.0?0.2?0.4???a )?1.0?0.2?1.4? (b)??1.00.40.8????1.0000??0.5000?0.3333??0.25000.50000.33330.25000.20000.33330.25000.20000.16670.2500??0.2000? 0.1667??0.1429?P120.3 Ð޸ijÌÐò3.3 Ö÷Òª±ä¶¯ÎªÁоØÕóB±ä³ÉÁ˵¥Î»¾ØÕóE Ëã·¨£º £¨1£© ÊäÈë A,E£»Áî[N,N]=size(A);X=zeros(N,1);Y=zeros(N,1);C=zeros(1,N);t=1:N; p=1¡£ £¨2£© ÅжÏp=1>N-1ÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬Ö´Ðв½Ö裨6£©£»Èô²»³ÉÁ¢£¬Ö´Ðв½Ö裨3£©¡£ £¨3£© [max1,j]=max(abs(A(p:N,p)));C=A(p,:);A(p,:)=A(j+p-1,:);A(j+p-1,:)=C;d=t(p);t(p)=t(j+p-1);t(j+p-1)=d; £¨4£© ÅжÏA(p,p)==0ÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬Ö´Ðв½Ö裨12£©£»Èô²»³ÉÁ¢£¬k=p+1£¬Ö´Ðв½Ö裨5£©¡£ £¨5£© ÅжÏk>NÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬·µ»Øµ½²½Ö裨2£©£»Èô²»³ÉÁ¢£¬ mult=A(k,p)/A(p,p); A(k,p)=mult;A(k,p+1:N)=A(k,p+1:N)-mult*A(p,p+1:N);k=k+1;·µ»Øµ½²½Ö裨5£©¡£ £¨6£© J=1¡£ £¨7£© ÅжÏJ>NÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬Ö´Ðв½Ö裨12£©£»Èô²»³ÉÁ¢£¬k=2, Y(1)=E(t(1),J);Ö´Ðв½ Ö裨8£© £¨8£© ÅжÏk>NÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬Ö´Ðв½Ö裨9£©£»Èô²»³ÉÁ¢£¬ Y(k)=E(t(k),J)-A(k,1:k-1)*Y(1:k-1)£¬k=k+1,·µ»Ø²½Ö裨8£©¡£ £¨9£© X(N)=Y(N)/A(N,N); k=N-1. £¨10£© ÅжÏk> 1ÊÇ·ñ³ÉÁ¢£¬Èô³ÉÁ¢£¬Ö´Ðв½Ö裨11£©£»Èô²»³ÉÁ¢£¬ X(k)=(Y(k)-A(k,k+1:N)*X(k+1:N))/A(k,k); k=k-1;Ö´Ðв½Ö裨10£©. £¨11£© m(1:N,J)=X(1:N);·µ»Ø²½Ö裨7£©. £¨12£© Êä³ö½á¹û¡£ Á÷³Ìͼ£º
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