Hi, working offline with Edmond we have solved my problem. The problem was that ROOT 4.0.8 was not able to invert a matrix that ROOT 3.4.2 was able to invert. My matrix had huge determinant (1E53) that caused problem to ROOT 4.0.8 when determinant calculation was explicitly asked. I used determinant computation just to catch singularity of the matrix. Edmond show me better ways of testing for singularity. Reconditioning my matrix by dividing every element by the maximum diagonal element make it more manageable for determinant computation and now both version of ROOT give identical results on this better behaved matrix. For those interested this is the matrix that new ROOT has problem to determine determinant: Matrix 21x21 is as follows | 0 | 1 | 2 | 3 | 4 | ------------------------------------------------------------------ 0 | 833 475 474.7 154.2 490.4 1 | 475 947.1 538.4 155.1 560.1 2 | 474.7 538.4 1016 148.9 601.5 3 | 154.2 155.1 148.9 250.7 169.4 4 | 490.4 560.1 601.5 169.4 1314 5 | 489.2 556.5 596.4 155.1 771.8 6 | 481.1 549.4 588.4 155.1 760.9 7 | 475.5 532.8 552.2 159.7 571.6 8 | 476.5 543.4 584.3 156.6 772.7 9 | 394.4 461.4 504.8 70.02 661.3 10 | 474 537.3 575.8 152.8 742 11 | 460.4 525.7 564.5 146.2 755.7 12 | 276.7 319.8 353.9 22.09 478.5 13 | 0 16.61 52.61 0 171.2 14 | 101.4 149.6 182 0 292.6 15 | 246.4 277.8 299.4 77.6 370.5 16 | 0 0 0 0 58.85 17 | 0 0 0 0 39.23 18 | 0 0 0 0 42.14 19 | 17.77 43.23 65.38 0 133.9 20 | 970.8 1107 1191 315.2 1545 | 5 | 6 | 7 | 8 | 9 | ------------------------------------------------------------------ 0 | 489.2 481.1 475.5 476.5 394.4 1 | 556.5 549.4 532.8 543.4 461.4 2 | 596.4 588.4 552.2 584.3 504.8 3 | 155.1 155.1 159.7 156.6 70.02 4 | 771.8 760.9 571.6 772.7 661.3 5 | 1365 781.8 567.4 792.9 703.6 6 | 781.8 1350 560.1 783.2 698.9 7 | 567.4 560.1 944.9 554.1 471.5 8 | 792.9 783.2 554.1 1342 711.2 9 | 703.6 698.9 471.5 711.2 1189 10 | 758.5 749.7 548.8 761.5 678.1 11 | 773.6 762.8 547.1 777.8 696.4 12 | 504.4 498.4 330.5 505.9 503.9 13 | 189.7 188.2 25.56 203.6 206 14 | 316.5 309.9 162.1 316.7 324.3 15 | 378.4 374.3 273.6 383.1 341.6 16 | 65.48 58.62 0 74.83 74.88 17 | 49.28 45.25 0 52.31 54.38 18 | 49.67 46.48 0 56.8 57.6 19 | 135 132.8 56.23 142.2 140.8 20 | 1581 1563 1131 1586 1409 | 10 | 11 | 12 | 13 | 14 | ------------------------------------------------------------------ 0 | 474 460.4 276.7 0 101.4 1 | 537.3 525.7 319.8 16.61 149.6 2 | 575.8 564.5 353.9 52.61 182 3 | 152.8 146.2 22.09 0 0 4 | 742 755.7 478.5 171.2 292.6 5 | 758.5 773.6 504.4 189.7 316.5 6 | 749.7 762.8 498.4 188.2 309.9 7 | 548.8 547.1 330.5 25.56 162.1 8 | 761.5 777.8 505.9 203.6 316.7 9 | 678.1 696.4 503.9 206 324.3 10 | 1295 756.2 505.3 199 278.9 11 | 756.2 1304 508.8 201.4 319.3 12 | 505.3 508.8 844.5 176.1 315 13 | 199 201.4 176.1 319 171.6 14 | 278.9 319.3 315 171.6 530.7 15 | 382.5 375.3 317.3 120.6 230.8 16 | 67.16 75.5 78.26 68.94 77.3 17 | 45.89 55.56 51.24 49.8 57.54 18 | 46.73 57.49 55.5 51.34 60.05 19 | 127.7 144.1 142.4 101.3 149.8 20 | 1525 1548 1010 390.6 630 | 15 | 16 | 17 | 18 | 19 | ------------------------------------------------------------------ 0 | 246.4 0 0 0 17.77 1 | 277.8 0 0 0 43.23 2 | 299.4 0 0 0 65.38 3 | 77.6 0 0 0 0 4 | 370.5 58.85 39.23 42.14 133.9 5 | 378.4 65.48 49.28 49.67 135 6 | 374.3 58.62 45.25 46.48 132.8 7 | 273.6 0 0 0 56.23 8 | 383.1 74.83 52.31 56.8 142.2 9 | 341.6 74.88 54.38 57.6 140.8 10 | 382.5 67.16 45.89 46.73 127.7 11 | 375.3 75.5 55.56 57.49 144.1 12 | 317.3 78.26 51.24 55.5 142.4 13 | 120.6 68.94 49.8 51.34 101.3 14 | 230.8 77.3 57.54 60.05 149.8 15 | 657.2 64.84 44.36 51 144 16 | 64.84 110.4 52.59 56 56.9 17 | 44.36 52.59 79.1 73.07 44.16 18 | 51 56 73.07 83.99 45.74 19 | 144 56.9 44.16 45.74 228.7 20 | 774 143.4 103.2 108 281.6 | 20 | ------------------------------------------------------------------ 0 | 970.8 1 | 1107 2 | 1191 3 | 315.2 4 | 1545 5 | 1581 6 | 1563 7 | 1131 8 | 1586 9 | 1409 10 | 1525 11 | 1548 12 | 1010 13 | 390.6 14 | 630 15 | 774 16 | 143.4 17 | 103.2 18 | 108 19 | 281.6 20 | 3168 determinant (as computed by ROOT 3) 136908227115674077978030740804195813377898749408313344.000000 Thanks -- Nicolas Produit INTEGRAL Science Data Center Phone: +41 22 950 91 40 16, Chemin d'Ecogia Fax: +41 22 950 91 33 CH-1290 Versoix www: http://isdc.unige.ch/~produit Phone after 10 Dec 2004: +41 22 379 21 40
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