pdenu22_eq.c running
         differential equation to solve 
 d^2u/dx^2 + 2*d^2u/dy^2 + 3*d^2u/dxdy + 4*du/dx + 5*du/dy +6*u = c(x,y) 
c(x,y)6x^3+12y^3+18x^2y+24xy^2+57x^2+82y^2+64xy+122x+114y+110 
non uniform grid on rectangle -1.0,-1.1 to 1.2,1.3 
known solution, U(x,y), to test method 
u(x,y) = x^3+2y^3+3x^2y+4xy^2+5x^2+6y^2+7x+8 
xmin=-1, xmax=1.2, nx=11 
ymin=-1.1, ymax=1.3, ny=10 
u(xg[1],yg[1])=2.991 
c(xg[1],yg[1])=19.416 
internal cells zeroed 
matrix initialized
exact solution u, computed us, error
xg[1]=-0.900000,yg[1]=-0.900000, u=2.991000, us=2.991000, err=-1.39891e-11 
xg[1]=-0.900000,yg[2]=-0.800000, u=3.320000, us=3.320000, err=-1.6125e-11 
xg[1]=-0.900000,yg[3]=-0.600000, u=3.995000, us=3.995000, err=-7.41367e-13 
xg[1]=-0.900000,yg[4]=-0.300000, u=4.615000, us=4.615000, err=-2.39189e-13 
xg[1]=-0.900000,yg[5]=0.000000, u=6.020000, us=6.020000, err=-1.19598e-12 
xg[1]=-0.900000,yg[6]=0.350000, u=9.525000, us=9.525000, err=-6.18049e-13 
xg[1]=-0.900000,yg[7]=0.650000, u=11.851000, us=11.851000, err=-7.64679e-13 
xg[1]=-0.900000,yg[8]=0.850000, u=14.849000, us=14.849000, err=1.74918e-13 
xg[2]=-0.800000,yg[1]=-0.900000, u=3.968000, us=3.968000, err=-1.90119e-11 
xg[2]=-0.800000,yg[2]=-0.800000, u=4.170000, us=4.170000, err=-2.77932e-11 
xg[2]=-0.800000,yg[3]=-0.600000, u=4.512000, us=4.512000, err=-1.29201e-11 
xg[2]=-0.800000,yg[4]=-0.300000, u=4.800000, us=4.800000, err=2.51451e-12 
xg[2]=-0.800000,yg[5]=0.000000, u=5.970000, us=5.970000, err=-3.49744e-12 
xg[2]=-0.800000,yg[6]=0.350000, u=9.440000, us=9.440000, err=-1.14495e-13 
xg[2]=-0.800000,yg[7]=0.650000, u=11.808000, us=11.808000, err=-9.30646e-13 
xg[2]=-0.800000,yg[8]=0.850000, u=14.880000, us=14.880000, err=-1.40146e-13 
xg[3]=-0.600000,yg[1]=-0.900000, u=5.904000, us=5.904000, err=-2.412e-11 
xg[3]=-0.600000,yg[2]=-0.800000, u=5.870000, us=5.870000, err=-3.89661e-11 
xg[3]=-0.600000,yg[3]=-0.600000, u=5.600000, us=5.600000, err=-4.10547e-11 
xg[3]=-0.600000,yg[4]=-0.300000, u=5.296000, us=5.296000, err=-6.62334e-12 
xg[3]=-0.600000,yg[5]=0.000000, u=6.086000, us=6.086000, err=-1.54752e-12 
xg[3]=-0.600000,yg[6]=0.350000, u=9.576000, us=9.576000, err=-1.3145e-12 
xg[3]=-0.600000,yg[7]=0.650000, u=12.064000, us=12.064000, err=-2.84219e-13 
xg[3]=-0.600000,yg[8]=0.850000, u=15.320000, us=15.320000, err=-4.25571e-13 
xg[4]=-0.300000,yg[1]=-0.900000, u=8.853000, us=8.853000, err=-2.73822e-11 
xg[4]=-0.300000,yg[2]=-0.800000, u=8.510000, us=8.510000, err=-4.94321e-11 
xg[4]=-0.300000,yg[3]=-0.600000, u=7.457000, us=7.457000, err=-6.92325e-11 
xg[4]=-0.300000,yg[4]=-0.300000, u=6.445000, us=6.445000, err=-3.67655e-11 
xg[4]=-0.300000,yg[5]=0.000000, u=6.890000, us=6.890000, err=-3.74601e-12 
xg[4]=-0.300000,yg[6]=0.350000, u=10.635000, us=10.635000, err=-2.23741e-12 
xg[4]=-0.300000,yg[7]=0.650000, u=13.393000, us=13.393000, err=-1.71835e-12 
xg[4]=-0.300000,yg[8]=0.850000, u=17.015000, us=17.015000, err=-2.25209e-13 
xg[5]=0.000000,yg[1]=-0.900000, u=12.000000, us=12.000000, err=-1.17168e-11 
xg[5]=0.000000,yg[2]=-0.800000, u=11.402000, us=11.402000, err=-3.02558e-11 
xg[5]=0.000000,yg[3]=-0.600000, u=9.728000, us=9.728000, err=-7.65964e-11 
xg[5]=0.000000,yg[4]=-0.300000, u=8.224000, us=8.224000, err=-6.26683e-11 
xg[5]=0.000000,yg[5]=0.000000, u=8.594000, us=8.594000, err=-1.70791e-11 
xg[5]=0.000000,yg[6]=0.350000, u=12.864000, us=12.864000, err=-2.00213e-12 
xg[5]=0.000000,yg[7]=0.650000, u=16.000000, us=16.000000, err=-1.32871e-12 
xg[5]=0.000000,yg[8]=0.850000, u=20.096000, us=20.096000, err=-7.64942e-13 
xg[6]=0.350000,yg[1]=-0.900000, u=16.137875, us=16.137875, err=9.08293e-12 
xg[6]=0.350000,yg[2]=-0.800000, u=15.310625, us=15.310625, err=1.05604e-11 
xg[6]=0.350000,yg[3]=-0.600000, u=13.116875, us=13.116875, err=-2.38341e-11 
xg[6]=0.350000,yg[4]=-0.300000, u=11.311875, us=11.311875, err=-6.6925e-11 
xg[6]=0.350000,yg[5]=0.000000, u=11.935625, us=11.935625, err=-3.225e-11 
xg[6]=0.350000,yg[6]=0.350000, u=17.159375, us=17.159375, err=-7.00984e-12 
xg[6]=0.350000,yg[7]=0.650000, u=20.872875, us=20.872875, err=-3.05622e-12 
xg[6]=0.350000,yg[8]=0.850000, u=25.658375, us=25.658375, err=-6.33486e-13 
xg[7]=0.650000,yg[1]=-0.900000, u=20.269625, us=20.269625, err=8.28747e-12 
xg[7]=0.650000,yg[2]=-0.800000, u=19.304375, us=19.304375, err=1.86911e-11 
xg[7]=0.650000,yg[3]=-0.600000, u=16.840625, us=16.840625, err=2.42801e-11 
xg[7]=0.650000,yg[4]=-0.300000, u=15.011625, us=15.011625, err=-2.43788e-11 
xg[7]=0.650000,yg[5]=0.000000, u=16.145375, us=16.145375, err=-3.84272e-11 
xg[7]=0.650000,yg[6]=0.350000, u=22.479125, us=22.479125, err=-9.68676e-12 
xg[7]=0.650000,yg[7]=0.650000, u=26.804625, us=26.804625, err=-4.78648e-12 
xg[7]=0.650000,yg[8]=0.850000, u=32.298125, us=32.298125, err=-1.69075e-12 
xg[8]=0.850000,yg[1]=-0.900000, u=23.409125, us=23.409125, err=-3.14404e-12 
xg[8]=0.850000,yg[2]=-0.800000, u=22.381875, us=22.381875, err=2.61735e-12 
xg[8]=0.850000,yg[3]=-0.600000, u=19.828125, us=19.828125, err=3.01798e-11 
xg[8]=0.850000,yg[4]=-0.300000, u=18.103125, us=18.103125, err=4.91091e-12 
xg[8]=0.850000,yg[5]=0.000000, u=19.726875, us=19.726875, err=-2.87168e-11 
xg[8]=0.850000,yg[6]=0.350000, u=26.950625, us=26.950625, err=-1.2479e-11 
xg[8]=0.850000,yg[7]=0.650000, u=31.744125, us=31.744125, err=-4.8291e-12 
xg[8]=0.850000,yg[8]=0.850000, u=37.769625, us=37.769625, err=-1.22916e-12 
xg[9]=1.000000,yg[1]=-0.900000, u=26.000000, us=26.000000, err=-8.63309e-12 
xg[9]=1.000000,yg[2]=-0.800000, u=24.942000, us=24.942000, err=-1.21858e-11 
xg[9]=1.000000,yg[3]=-0.600000, u=22.368000, us=22.368000, err=1.62479e-11 
xg[9]=1.000000,yg[4]=-0.300000, u=20.784000, us=20.784000, err=2.12747e-11 
xg[9]=1.000000,yg[5]=0.000000, u=22.854000, us=22.854000, err=-1.92408e-11 
xg[9]=1.000000,yg[6]=0.350000, u=30.824000, us=30.824000, err=-1.23854e-11 
xg[9]=1.000000,yg[7]=0.650000, u=36.000000, us=36.000000, err=-6.75726e-12 
xg[9]=1.000000,yg[8]=0.850000, u=42.456000, us=42.456000, err=4.78517e-13 

total error=1.07714e-09, average error=1.49603e-11, max error=7.65965e-11