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