1 #define PETSCMAT_DLL 2 3 /* 4 Inverts 7 by 7 matrix using partial pivoting. 5 6 Used by the sparse factorization routines in 7 src/mat/impls/baij/seq 8 9 See also src/inline/ilu.h 10 11 This is a combination of the Linpack routines 12 dgefa() and dgedi() specialized for a size of 7. 13 14 */ 15 #include "petsc.h" 16 17 #undef __FUNCT__ 18 #define __FUNCT__ "Kernel_A_gets_inverse_A_7" 19 PetscErrorCode Kernel_A_gets_inverse_A_7(MatScalar *a,PetscReal shift) 20 { 21 PetscInt i__2,i__3,kp1,j,k,l,ll,i,ipvt[7],kb,k3; 22 PetscInt k4,j3; 23 MatScalar *aa,*ax,*ay,work[49],stmp; 24 MatReal tmp,max; 25 26 /* gaussian elimination with partial pivoting */ 27 28 PetscFunctionBegin; 29 /* Parameter adjustments */ 30 a -= 8; 31 32 for (k = 1; k <= 6; ++k) { 33 kp1 = k + 1; 34 k3 = 7*k; 35 k4 = k3 + k; 36 /* find l = pivot index */ 37 38 i__2 = 8 - k; 39 aa = &a[k4]; 40 max = PetscAbsScalar(aa[0]); 41 l = 1; 42 for (ll=1; ll<i__2; ll++) { 43 tmp = PetscAbsScalar(aa[ll]); 44 if (tmp > max) { max = tmp; l = ll+1;} 45 } 46 l += k - 1; 47 ipvt[k-1] = l; 48 49 if (a[l + k3] == 0.0) { 50 SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1); 51 } 52 53 /* interchange if necessary */ 54 55 if (l != k) { 56 stmp = a[l + k3]; 57 a[l + k3] = a[k4]; 58 a[k4] = stmp; 59 } 60 61 /* compute multipliers */ 62 63 stmp = -1. / a[k4]; 64 i__2 = 7 - k; 65 aa = &a[1 + k4]; 66 for (ll=0; ll<i__2; ll++) { 67 aa[ll] *= stmp; 68 } 69 70 /* row elimination with column indexing */ 71 72 ax = &a[k4+1]; 73 for (j = kp1; j <= 7; ++j) { 74 j3 = 7*j; 75 stmp = a[l + j3]; 76 if (l != k) { 77 a[l + j3] = a[k + j3]; 78 a[k + j3] = stmp; 79 } 80 81 i__3 = 7 - k; 82 ay = &a[1+k+j3]; 83 for (ll=0; ll<i__3; ll++) { 84 ay[ll] += stmp*ax[ll]; 85 } 86 } 87 } 88 ipvt[6] = 7; 89 if (a[56] == 0.0) { 90 SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",6); 91 } 92 93 /* 94 Now form the inverse 95 */ 96 97 /* compute inverse(u) */ 98 99 for (k = 1; k <= 7; ++k) { 100 k3 = 7*k; 101 k4 = k3 + k; 102 a[k4] = 1.0 / a[k4]; 103 stmp = -a[k4]; 104 i__2 = k - 1; 105 aa = &a[k3 + 1]; 106 for (ll=0; ll<i__2; ll++) aa[ll] *= stmp; 107 kp1 = k + 1; 108 if (7 < kp1) continue; 109 ax = aa; 110 for (j = kp1; j <= 7; ++j) { 111 j3 = 7*j; 112 stmp = a[k + j3]; 113 a[k + j3] = 0.0; 114 ay = &a[j3 + 1]; 115 for (ll=0; ll<k; ll++) { 116 ay[ll] += stmp*ax[ll]; 117 } 118 } 119 } 120 121 /* form inverse(u)*inverse(l) */ 122 123 for (kb = 1; kb <= 6; ++kb) { 124 k = 7 - kb; 125 k3 = 7*k; 126 kp1 = k + 1; 127 aa = a + k3; 128 for (i = kp1; i <= 7; ++i) { 129 work[i-1] = aa[i]; 130 aa[i] = 0.0; 131 } 132 for (j = kp1; j <= 7; ++j) { 133 stmp = work[j-1]; 134 ax = &a[7*j + 1]; 135 ay = &a[k3 + 1]; 136 ay[0] += stmp*ax[0]; 137 ay[1] += stmp*ax[1]; 138 ay[2] += stmp*ax[2]; 139 ay[3] += stmp*ax[3]; 140 ay[4] += stmp*ax[4]; 141 ay[5] += stmp*ax[5]; 142 ay[6] += stmp*ax[6]; 143 } 144 l = ipvt[k-1]; 145 if (l != k) { 146 ax = &a[k3 + 1]; 147 ay = &a[7*l + 1]; 148 stmp = ax[0]; ax[0] = ay[0]; ay[0] = stmp; 149 stmp = ax[1]; ax[1] = ay[1]; ay[1] = stmp; 150 stmp = ax[2]; ax[2] = ay[2]; ay[2] = stmp; 151 stmp = ax[3]; ax[3] = ay[3]; ay[3] = stmp; 152 stmp = ax[4]; ax[4] = ay[4]; ay[4] = stmp; 153 stmp = ax[5]; ax[5] = ay[5]; ay[5] = stmp; 154 stmp = ax[6]; ax[6] = ay[6]; ay[6] = stmp; 155 } 156 } 157 PetscFunctionReturn(0); 158 } 159 160 161