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Diffstat (limited to 'src/fortran/lapack/dgeqpf.f')
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diff --git a/src/fortran/lapack/dgeqpf.f b/src/fortran/lapack/dgeqpf.f new file mode 100644 index 0000000..1b7acd6 --- /dev/null +++ b/src/fortran/lapack/dgeqpf.f @@ -0,0 +1,231 @@ + SUBROUTINE DGEQPF( M, N, A, LDA, JPVT, TAU, WORK, INFO ) +* +* -- LAPACK deprecated driver routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER INFO, LDA, M, N +* .. +* .. Array Arguments .. + INTEGER JPVT( * ) + DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * ) +* .. +* +* Purpose +* ======= +* +* This routine is deprecated and has been replaced by routine DGEQP3. +* +* DGEQPF computes a QR factorization with column pivoting of a +* real M-by-N matrix A: A*P = Q*R. +* +* Arguments +* ========= +* +* M (input) INTEGER +* The number of rows of the matrix A. M >= 0. +* +* N (input) INTEGER +* The number of columns of the matrix A. N >= 0 +* +* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) +* On entry, the M-by-N matrix A. +* On exit, the upper triangle of the array contains the +* min(M,N)-by-N upper triangular matrix R; the elements +* below the diagonal, together with the array TAU, +* represent the orthogonal matrix Q as a product of +* min(m,n) elementary reflectors. +* +* LDA (input) INTEGER +* The leading dimension of the array A. LDA >= max(1,M). +* +* JPVT (input/output) INTEGER array, dimension (N) +* On entry, if JPVT(i) .ne. 0, the i-th column of A is permuted +* to the front of A*P (a leading column); if JPVT(i) = 0, +* the i-th column of A is a free column. +* On exit, if JPVT(i) = k, then the i-th column of A*P +* was the k-th column of A. +* +* TAU (output) DOUBLE PRECISION array, dimension (min(M,N)) +* The scalar factors of the elementary reflectors. +* +* WORK (workspace) DOUBLE PRECISION array, dimension (3*N) +* +* INFO (output) INTEGER +* = 0: successful exit +* < 0: if INFO = -i, the i-th argument had an illegal value +* +* Further Details +* =============== +* +* The matrix Q is represented as a product of elementary reflectors +* +* Q = H(1) H(2) . . . H(n) +* +* Each H(i) has the form +* +* H = I - tau * v * v' +* +* where tau is a real scalar, and v is a real vector with +* v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i). +* +* The matrix P is represented in jpvt as follows: If +* jpvt(j) = i +* then the jth column of P is the ith canonical unit vector. +* +* Partial column norm updating strategy modified by +* Z. Drmac and Z. Bujanovic, Dept. of Mathematics, +* University of Zagreb, Croatia. +* June 2006. +* For more details see LAPACK Working Note 176. +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ZERO, ONE + PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 ) +* .. +* .. Local Scalars .. + INTEGER I, ITEMP, J, MA, MN, PVT + DOUBLE PRECISION AII, TEMP, TEMP2, TOL3Z +* .. +* .. External Subroutines .. + EXTERNAL DGEQR2, DLARF, DLARFG, DORM2R, DSWAP, XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC ABS, MAX, MIN, SQRT +* .. +* .. External Functions .. + INTEGER IDAMAX + DOUBLE PRECISION DLAMCH, DNRM2 + EXTERNAL IDAMAX, DLAMCH, DNRM2 +* .. +* .. Executable Statements .. +* +* Test the input arguments +* + INFO = 0 + IF( M.LT.0 ) THEN + INFO = -1 + ELSE IF( N.LT.0 ) THEN + INFO = -2 + ELSE IF( LDA.LT.MAX( 1, M ) ) THEN + INFO = -4 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'DGEQPF', -INFO ) + RETURN + END IF +* + MN = MIN( M, N ) + TOL3Z = SQRT(DLAMCH('Epsilon')) +* +* Move initial columns up front +* + ITEMP = 1 + DO 10 I = 1, N + IF( JPVT( I ).NE.0 ) THEN + IF( I.NE.ITEMP ) THEN + CALL DSWAP( M, A( 1, I ), 1, A( 1, ITEMP ), 1 ) + JPVT( I ) = JPVT( ITEMP ) + JPVT( ITEMP ) = I + ELSE + JPVT( I ) = I + END IF + ITEMP = ITEMP + 1 + ELSE + JPVT( I ) = I + END IF + 10 CONTINUE + ITEMP = ITEMP - 1 +* +* Compute the QR factorization and update remaining columns +* + IF( ITEMP.GT.0 ) THEN + MA = MIN( ITEMP, M ) + CALL DGEQR2( M, MA, A, LDA, TAU, WORK, INFO ) + IF( MA.LT.N ) THEN + CALL DORM2R( 'Left', 'Transpose', M, N-MA, MA, A, LDA, TAU, + $ A( 1, MA+1 ), LDA, WORK, INFO ) + END IF + END IF +* + IF( ITEMP.LT.MN ) THEN +* +* Initialize partial column norms. The first n elements of +* work store the exact column norms. +* + DO 20 I = ITEMP + 1, N + WORK( I ) = DNRM2( M-ITEMP, A( ITEMP+1, I ), 1 ) + WORK( N+I ) = WORK( I ) + 20 CONTINUE +* +* Compute factorization +* + DO 40 I = ITEMP + 1, MN +* +* Determine ith pivot column and swap if necessary +* + PVT = ( I-1 ) + IDAMAX( N-I+1, WORK( I ), 1 ) +* + IF( PVT.NE.I ) THEN + CALL DSWAP( M, A( 1, PVT ), 1, A( 1, I ), 1 ) + ITEMP = JPVT( PVT ) + JPVT( PVT ) = JPVT( I ) + JPVT( I ) = ITEMP + WORK( PVT ) = WORK( I ) + WORK( N+PVT ) = WORK( N+I ) + END IF +* +* Generate elementary reflector H(i) +* + IF( I.LT.M ) THEN + CALL DLARFG( M-I+1, A( I, I ), A( I+1, I ), 1, TAU( I ) ) + ELSE + CALL DLARFG( 1, A( M, M ), A( M, M ), 1, TAU( M ) ) + END IF +* + IF( I.LT.N ) THEN +* +* Apply H(i) to A(i:m,i+1:n) from the left +* + AII = A( I, I ) + A( I, I ) = ONE + CALL DLARF( 'LEFT', M-I+1, N-I, A( I, I ), 1, TAU( I ), + $ A( I, I+1 ), LDA, WORK( 2*N+1 ) ) + A( I, I ) = AII + END IF +* +* Update partial column norms +* + DO 30 J = I + 1, N + IF( WORK( J ).NE.ZERO ) THEN +* +* NOTE: The following 4 lines follow from the analysis in +* Lapack Working Note 176. +* + TEMP = ABS( A( I, J ) ) / WORK( J ) + TEMP = MAX( ZERO, ( ONE+TEMP )*( ONE-TEMP ) ) + TEMP2 = TEMP*( WORK( J ) / WORK( N+J ) )**2 + IF( TEMP2 .LE. TOL3Z ) THEN + IF( M-I.GT.0 ) THEN + WORK( J ) = DNRM2( M-I, A( I+1, J ), 1 ) + WORK( N+J ) = WORK( J ) + ELSE + WORK( J ) = ZERO + WORK( N+J ) = ZERO + END IF + ELSE + WORK( J ) = WORK( J )*SQRT( TEMP ) + END IF + END IF + 30 CONTINUE +* + 40 CONTINUE + END IF + RETURN +* +* End of DGEQPF +* + END |