| SUBROUTINE CGETRSF( TRANS, N, NRHS, A, LDA, IPIV, B, LDB, INFO ) |
| * |
| * -- LAPACK routine (version 3.0) -- |
| * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., |
| * Courant Institute, Argonne National Lab, and Rice University |
| * September 30, 1994 |
| * |
| * .. Scalar Arguments .. |
| CHARACTER TRANS |
| INTEGER INFO, LDA, LDB, N, NRHS |
| * .. |
| * .. Array Arguments .. |
| INTEGER IPIV( * ) |
| COMPLEX A( LDA, * ), B( LDB, * ) |
| * .. |
| * |
| * Purpose |
| * ======= |
| * |
| * CGETRS solves a system of linear equations |
| * A * X = B, A**T * X = B, or A**H * X = B |
| * with a general N-by-N matrix A using the LU factorization computed |
| * by CGETRF. |
| * |
| * Arguments |
| * ========= |
| * |
| * TRANS (input) CHARACTER*1 |
| * Specifies the form of the system of equations: |
| * = 'N': A * X = B (No transpose) |
| * = 'T': A**T * X = B (Transpose) |
| * = 'C': A**H * X = B (Conjugate transpose) |
| * |
| * N (input) INTEGER |
| * The order of the matrix A. N >= 0. |
| * |
| * NRHS (input) INTEGER |
| * The number of right hand sides, i.e., the number of columns |
| * of the matrix B. NRHS >= 0. |
| * |
| * A (input) COMPLEX array, dimension (LDA,N) |
| * The factors L and U from the factorization A = P*L*U |
| * as computed by CGETRF. |
| * |
| * LDA (input) INTEGER |
| * The leading dimension of the array A. LDA >= max(1,N). |
| * |
| * IPIV (input) INTEGER array, dimension (N) |
| * The pivot indices from CGETRF; for 1<=i<=N, row i of the |
| * matrix was interchanged with row IPIV(i). |
| * |
| * B (input/output) COMPLEX array, dimension (LDB,NRHS) |
| * On entry, the right hand side matrix B. |
| * On exit, the solution matrix X. |
| * |
| * LDB (input) INTEGER |
| * The leading dimension of the array B. LDB >= max(1,N). |
| * |
| * INFO (output) INTEGER |
| * = 0: successful exit |
| * < 0: if INFO = -i, the i-th argument had an illegal value |
| * |
| * ===================================================================== |
| * |
| * .. Parameters .. |
| COMPLEX ONE |
| PARAMETER ( ONE = ( 1.0E+0, 0.0E+0 ) ) |
| * .. |
| * .. Local Scalars .. |
| LOGICAL NOTRAN |
| * .. |
| * .. External Functions .. |
| LOGICAL LSAME |
| EXTERNAL LSAME |
| * .. |
| * .. External Subroutines .. |
| EXTERNAL CLASWP, CTRSM, XERBLA |
| * .. |
| * .. Intrinsic Functions .. |
| INTRINSIC MAX |
| * .. |
| * .. Executable Statements .. |
| * |
| * Test the input parameters. |
| * |
| INFO = 0 |
| NOTRAN = LSAME( TRANS, 'N' ) .OR. LSAME(TRANS, 'R') |
| IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'T' ) .AND. .NOT. |
| $ LSAME( TRANS, 'C' ) ) THEN |
| INFO = -1 |
| ELSE IF( N.LT.0 ) THEN |
| INFO = -2 |
| ELSE IF( NRHS.LT.0 ) THEN |
| INFO = -3 |
| ELSE IF( LDA.LT.MAX( 1, N ) ) THEN |
| INFO = -5 |
| ELSE IF( LDB.LT.MAX( 1, N ) ) THEN |
| INFO = -8 |
| END IF |
| IF( INFO.NE.0 ) THEN |
| CALL XERBLA( 'CGETRS', -INFO ) |
| RETURN |
| END IF |
| * |
| * Quick return if possible |
| * |
| IF( N.EQ.0 .OR. NRHS.EQ.0 ) |
| $ RETURN |
| * |
| IF( NOTRAN ) THEN |
| * |
| * Solve A * X = B. |
| * |
| * Apply row interchanges to the right hand sides. |
| * |
| CALL CLASWP( NRHS, B, LDB, 1, N, IPIV, 1 ) |
| * |
| * Solve L*X = B, overwriting B with X. |
| * |
| CALL CTRSM( 'Left', 'Lower', TRANS, 'Unit', N, NRHS, |
| $ ONE, A, LDA, B, LDB ) |
| * |
| * Solve U*X = B, overwriting B with X. |
| * |
| CALL CTRSM( 'Left', 'Upper', TRANS, 'Non-unit', N, |
| $ NRHS, ONE, A, LDA, B, LDB ) |
| ELSE |
| * |
| * Solve A**T * X = B or A**H * X = B. |
| * |
| * Solve U'*X = B, overwriting B with X. |
| * |
| CALL CTRSM( 'Left', 'Upper', TRANS, 'Non-unit', N, NRHS, ONE, |
| $ A, LDA, B, LDB ) |
| * |
| * Solve L'*X = B, overwriting B with X. |
| * |
| CALL CTRSM( 'Left', 'Lower', TRANS, 'Unit', N, NRHS, ONE, A, |
| $ LDA, B, LDB ) |
| * |
| * Apply row interchanges to the solution vectors. |
| * |
| CALL CLASWP( NRHS, B, LDB, 1, N, IPIV, -1 ) |
| END IF |
| * |
| RETURN |
| * |
| * End of CGETRS |
| * |
| END |
