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1 SUBROUTINE ZPOTRI( UPLO, N, A, LDA, INFO ) |
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2 * |
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3 * -- LAPACK routine (version 3.0) -- |
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4 * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., |
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5 * Courant Institute, Argonne National Lab, and Rice University |
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6 * March 31, 1993 |
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7 * |
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8 * .. Scalar Arguments .. |
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9 CHARACTER UPLO |
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10 INTEGER INFO, LDA, N |
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11 * .. |
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12 * .. Array Arguments .. |
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13 COMPLEX*16 A( LDA, * ) |
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14 * .. |
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15 * |
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16 * Purpose |
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17 * ======= |
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18 * |
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19 * ZPOTRI computes the inverse of a complex Hermitian positive definite |
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20 * matrix A using the Cholesky factorization A = U**H*U or A = L*L**H |
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21 * computed by ZPOTRF. |
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22 * |
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23 * Arguments |
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24 * ========= |
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25 * |
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26 * UPLO (input) CHARACTER*1 |
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27 * = 'U': Upper triangle of A is stored; |
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28 * = 'L': Lower triangle of A is stored. |
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29 * |
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30 * N (input) INTEGER |
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31 * The order of the matrix A. N >= 0. |
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32 * |
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33 * A (input/output) COMPLEX*16 array, dimension (LDA,N) |
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34 * On entry, the triangular factor U or L from the Cholesky |
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35 * factorization A = U**H*U or A = L*L**H, as computed by |
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36 * ZPOTRF. |
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37 * On exit, the upper or lower triangle of the (Hermitian) |
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38 * inverse of A, overwriting the input factor U or L. |
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39 * |
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40 * LDA (input) INTEGER |
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41 * The leading dimension of the array A. LDA >= max(1,N). |
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42 * |
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43 * INFO (output) INTEGER |
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44 * = 0: successful exit |
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45 * < 0: if INFO = -i, the i-th argument had an illegal value |
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46 * > 0: if INFO = i, the (i,i) element of the factor U or L is |
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47 * zero, and the inverse could not be computed. |
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48 * |
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49 * ===================================================================== |
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50 * |
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51 * .. External Functions .. |
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52 LOGICAL LSAME |
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53 EXTERNAL LSAME |
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54 * .. |
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55 * .. External Subroutines .. |
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56 EXTERNAL XERBLA, ZLAUUM, ZTRTRI |
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57 * .. |
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58 * .. Intrinsic Functions .. |
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59 INTRINSIC MAX |
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60 * .. |
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61 * .. Executable Statements .. |
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62 * |
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63 * Test the input parameters. |
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64 * |
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65 INFO = 0 |
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66 IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN |
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67 INFO = -1 |
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68 ELSE IF( N.LT.0 ) THEN |
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69 INFO = -2 |
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70 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN |
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71 INFO = -4 |
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72 END IF |
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73 IF( INFO.NE.0 ) THEN |
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74 CALL XERBLA( 'ZPOTRI', -INFO ) |
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75 RETURN |
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76 END IF |
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77 * |
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78 * Quick return if possible |
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79 * |
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80 IF( N.EQ.0 ) |
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81 $ RETURN |
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82 * |
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83 * Invert the triangular Cholesky factor U or L. |
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84 * |
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85 CALL ZTRTRI( UPLO, 'Non-unit', N, A, LDA, INFO ) |
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86 IF( INFO.GT.0 ) |
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87 $ RETURN |
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88 * |
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89 * Form inv(U)*inv(U)' or inv(L)'*inv(L). |
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90 * |
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91 CALL ZLAUUM( UPLO, N, A, LDA, INFO ) |
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92 * |
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93 RETURN |
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94 * |
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95 * End of ZPOTRI |
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96 * |
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97 END |
