void spslb(float **ab, int n, int m, float *b)
	{int k,la,lb,lm; float t;
	for (k=1;k<=n;k++)
		{lm= (k <= m)? k-1 : m;
		la=m-lm;
		lb=k-1-lm;
		t=vdot(lm,&ab[k][la],&b[lb]);
		b[k] -= t; b[k] /= ab[k][m+1];}
	for (k=n;k>=1;k--)
		{lm= (k <= m)? k-1 : m;
		la=m-lm;
		lb=k-1-lm;
		b[k] /= ab[k][m+1];
		vmsv(lm,b[k],&ab[k][la],&b[lb]);}
	}