diff options
author | jason <jason@8a072113-8704-0410-8d35-dd094bca7971> | 2008-10-28 01:38:50 +0000 |
---|---|---|
committer | jason <jason@8a072113-8704-0410-8d35-dd094bca7971> | 2008-10-28 01:38:50 +0000 |
commit | baba851215b44ac3b60b9248eb02bcce7eb76247 (patch) | |
tree | 8c0f5c006875532a30d4409f5e94b0f310ff00a7 /SRC/zgtts2.f | |
download | lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.gz lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.bz2 lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.zip |
Move LAPACK trunk into position.
Diffstat (limited to 'SRC/zgtts2.f')
-rw-r--r-- | SRC/zgtts2.f | 271 |
1 files changed, 271 insertions, 0 deletions
diff --git a/SRC/zgtts2.f b/SRC/zgtts2.f new file mode 100644 index 00000000..da6073d8 --- /dev/null +++ b/SRC/zgtts2.f @@ -0,0 +1,271 @@ + SUBROUTINE ZGTTS2( ITRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER ITRANS, LDB, N, NRHS +* .. +* .. Array Arguments .. + INTEGER IPIV( * ) + COMPLEX*16 B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * ) +* .. +* +* Purpose +* ======= +* +* ZGTTS2 solves one of the systems of equations +* A * X = B, A**T * X = B, or A**H * X = B, +* with a tridiagonal matrix A using the LU factorization computed +* by ZGTTRF. +* +* Arguments +* ========= +* +* ITRANS (input) INTEGER +* Specifies the form of the system of equations. +* = 0: A * X = B (No transpose) +* = 1: A**T * X = B (Transpose) +* = 2: A**H * X = B (Conjugate transpose) +* +* N (input) INTEGER +* The order of the matrix A. +* +* NRHS (input) INTEGER +* The number of right hand sides, i.e., the number of columns +* of the matrix B. NRHS >= 0. +* +* DL (input) COMPLEX*16 array, dimension (N-1) +* The (n-1) multipliers that define the matrix L from the +* LU factorization of A. +* +* D (input) COMPLEX*16 array, dimension (N) +* The n diagonal elements of the upper triangular matrix U from +* the LU factorization of A. +* +* DU (input) COMPLEX*16 array, dimension (N-1) +* The (n-1) elements of the first super-diagonal of U. +* +* DU2 (input) COMPLEX*16 array, dimension (N-2) +* The (n-2) elements of the second super-diagonal of U. +* +* IPIV (input) INTEGER array, dimension (N) +* The pivot indices; for 1 <= i <= n, row i of the matrix was +* interchanged with row IPIV(i). IPIV(i) will always be either +* i or i+1; IPIV(i) = i indicates a row interchange was not +* required. +* +* B (input/output) COMPLEX*16 array, dimension (LDB,NRHS) +* On entry, the matrix of right hand side vectors B. +* On exit, B is overwritten by the solution vectors X. +* +* LDB (input) INTEGER +* The leading dimension of the array B. LDB >= max(1,N). +* +* ===================================================================== +* +* .. Local Scalars .. + INTEGER I, J + COMPLEX*16 TEMP +* .. +* .. Intrinsic Functions .. + INTRINSIC DCONJG +* .. +* .. Executable Statements .. +* +* Quick return if possible +* + IF( N.EQ.0 .OR. NRHS.EQ.0 ) + $ RETURN +* + IF( ITRANS.EQ.0 ) THEN +* +* Solve A*X = B using the LU factorization of A, +* overwriting each right hand side vector with its solution. +* + IF( NRHS.LE.1 ) THEN + J = 1 + 10 CONTINUE +* +* Solve L*x = b. +* + DO 20 I = 1, N - 1 + IF( IPIV( I ).EQ.I ) THEN + B( I+1, J ) = B( I+1, J ) - DL( I )*B( I, J ) + ELSE + TEMP = B( I, J ) + B( I, J ) = B( I+1, J ) + B( I+1, J ) = TEMP - DL( I )*B( I, J ) + END IF + 20 CONTINUE +* +* Solve U*x = b. +* + B( N, J ) = B( N, J ) / D( N ) + IF( N.GT.1 ) + $ B( N-1, J ) = ( B( N-1, J )-DU( N-1 )*B( N, J ) ) / + $ D( N-1 ) + DO 30 I = N - 2, 1, -1 + B( I, J ) = ( B( I, J )-DU( I )*B( I+1, J )-DU2( I )* + $ B( I+2, J ) ) / D( I ) + 30 CONTINUE + IF( J.LT.NRHS ) THEN + J = J + 1 + GO TO 10 + END IF + ELSE + DO 60 J = 1, NRHS +* +* Solve L*x = b. +* + DO 40 I = 1, N - 1 + IF( IPIV( I ).EQ.I ) THEN + B( I+1, J ) = B( I+1, J ) - DL( I )*B( I, J ) + ELSE + TEMP = B( I, J ) + B( I, J ) = B( I+1, J ) + B( I+1, J ) = TEMP - DL( I )*B( I, J ) + END IF + 40 CONTINUE +* +* Solve U*x = b. +* + B( N, J ) = B( N, J ) / D( N ) + IF( N.GT.1 ) + $ B( N-1, J ) = ( B( N-1, J )-DU( N-1 )*B( N, J ) ) / + $ D( N-1 ) + DO 50 I = N - 2, 1, -1 + B( I, J ) = ( B( I, J )-DU( I )*B( I+1, J )-DU2( I )* + $ B( I+2, J ) ) / D( I ) + 50 CONTINUE + 60 CONTINUE + END IF + ELSE IF( ITRANS.EQ.1 ) THEN +* +* Solve A**T * X = B. +* + IF( NRHS.LE.1 ) THEN + J = 1 + 70 CONTINUE +* +* Solve U**T * x = b. +* + B( 1, J ) = B( 1, J ) / D( 1 ) + IF( N.GT.1 ) + $ B( 2, J ) = ( B( 2, J )-DU( 1 )*B( 1, J ) ) / D( 2 ) + DO 80 I = 3, N + B( I, J ) = ( B( I, J )-DU( I-1 )*B( I-1, J )-DU2( I-2 )* + $ B( I-2, J ) ) / D( I ) + 80 CONTINUE +* +* Solve L**T * x = b. +* + DO 90 I = N - 1, 1, -1 + IF( IPIV( I ).EQ.I ) THEN + B( I, J ) = B( I, J ) - DL( I )*B( I+1, J ) + ELSE + TEMP = B( I+1, J ) + B( I+1, J ) = B( I, J ) - DL( I )*TEMP + B( I, J ) = TEMP + END IF + 90 CONTINUE + IF( J.LT.NRHS ) THEN + J = J + 1 + GO TO 70 + END IF + ELSE + DO 120 J = 1, NRHS +* +* Solve U**T * x = b. +* + B( 1, J ) = B( 1, J ) / D( 1 ) + IF( N.GT.1 ) + $ B( 2, J ) = ( B( 2, J )-DU( 1 )*B( 1, J ) ) / D( 2 ) + DO 100 I = 3, N + B( I, J ) = ( B( I, J )-DU( I-1 )*B( I-1, J )- + $ DU2( I-2 )*B( I-2, J ) ) / D( I ) + 100 CONTINUE +* +* Solve L**T * x = b. +* + DO 110 I = N - 1, 1, -1 + IF( IPIV( I ).EQ.I ) THEN + B( I, J ) = B( I, J ) - DL( I )*B( I+1, J ) + ELSE + TEMP = B( I+1, J ) + B( I+1, J ) = B( I, J ) - DL( I )*TEMP + B( I, J ) = TEMP + END IF + 110 CONTINUE + 120 CONTINUE + END IF + ELSE +* +* Solve A**H * X = B. +* + IF( NRHS.LE.1 ) THEN + J = 1 + 130 CONTINUE +* +* Solve U**H * x = b. +* + B( 1, J ) = B( 1, J ) / DCONJG( D( 1 ) ) + IF( N.GT.1 ) + $ B( 2, J ) = ( B( 2, J )-DCONJG( DU( 1 ) )*B( 1, J ) ) / + $ DCONJG( D( 2 ) ) + DO 140 I = 3, N + B( I, J ) = ( B( I, J )-DCONJG( DU( I-1 ) )*B( I-1, J )- + $ DCONJG( DU2( I-2 ) )*B( I-2, J ) ) / + $ DCONJG( D( I ) ) + 140 CONTINUE +* +* Solve L**H * x = b. +* + DO 150 I = N - 1, 1, -1 + IF( IPIV( I ).EQ.I ) THEN + B( I, J ) = B( I, J ) - DCONJG( DL( I ) )*B( I+1, J ) + ELSE + TEMP = B( I+1, J ) + B( I+1, J ) = B( I, J ) - DCONJG( DL( I ) )*TEMP + B( I, J ) = TEMP + END IF + 150 CONTINUE + IF( J.LT.NRHS ) THEN + J = J + 1 + GO TO 130 + END IF + ELSE + DO 180 J = 1, NRHS +* +* Solve U**H * x = b. +* + B( 1, J ) = B( 1, J ) / DCONJG( D( 1 ) ) + IF( N.GT.1 ) + $ B( 2, J ) = ( B( 2, J )-DCONJG( DU( 1 ) )*B( 1, J ) ) + $ / DCONJG( D( 2 ) ) + DO 160 I = 3, N + B( I, J ) = ( B( I, J )-DCONJG( DU( I-1 ) )* + $ B( I-1, J )-DCONJG( DU2( I-2 ) )* + $ B( I-2, J ) ) / DCONJG( D( I ) ) + 160 CONTINUE +* +* Solve L**H * x = b. +* + DO 170 I = N - 1, 1, -1 + IF( IPIV( I ).EQ.I ) THEN + B( I, J ) = B( I, J ) - DCONJG( DL( I ) )* + $ B( I+1, J ) + ELSE + TEMP = B( I+1, J ) + B( I+1, J ) = B( I, J ) - DCONJG( DL( I ) )*TEMP + B( I, J ) = TEMP + END IF + 170 CONTINUE + 180 CONTINUE + END IF + END IF +* +* End of ZGTTS2 +* + END |