Actual source code: dgefa7.c

  1: #define PETSCMAT_DLL

  3: /*
  4:       Inverts 7 by 7 matrix using partial pivoting.

  6:        Used by the sparse factorization routines in 
  7:      src/mat/impls/baij/seq

  9:        This is a combination of the Linpack routines
 10:     dgefa() and dgedi() specialized for a size of 7.

 12: */
 13:  #include petscsys.h

 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;

 24: /*     gaussian elimination with partial pivoting */

 27:     /* Parameter adjustments */
 28:     a       -= 8;

 30:     for (k = 1; k <= 6; ++k) {
 31:         kp1 = k + 1;
 32:         k3  = 7*k;
 33:         k4  = k3 + k;
 34: /*        find l = pivot index */

 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;

 47:         if (a[l + k3] == 0.0) {
 48:           SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1);
 49:         }

 51: /*           interchange if necessary */

 53:         if (l != k) {
 54:           stmp      = a[l + k3];
 55:           a[l + k3] = a[k4];
 56:           a[k4]     = stmp;
 57:         }

 59: /*           compute multipliers */

 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:         }

 68: /*           row elimination with column indexing */

 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:             }

 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:     }

 91:     /*
 92:          Now form the inverse 
 93:     */

 95:    /*     compute inverse(u) */

 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:     }

119:    /*    form inverse(u)*inverse(l) */

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:     return(0);
156: }