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gobyexample/third_party/pygments/tests/examplefiles/ahcon.f
Hana 9e216da9ef go.mod: add go.mod and move pygments to third_party 
After go1.16, go will use module mode by default,
even when the repository is checked out under GOPATH
or in a one-off directory. Add go.mod, go.sum to keep
this repo buildable without opting out of the module
mode.

> go mod init github.com/mmcgrana/gobyexample
> go mod tidy
> go mod vendor

In module mode, the 'vendor' directory is special
and its contents will be actively maintained by the
go command. pygments aren't the dependency the go will
know about, so it will delete the contents from vendor
directory. Move it to `third_party` directory now.

And, vendor the blackfriday package.

Note: the tutorial contents are not affected by the
change in go1.16 because all the examples in this
tutorial ask users to run the go command with the
explicit list of files to be compiled (e.g.
`go run hello-world.go` or `go build command-line-arguments.go`).
When the source list is provided, the go command does
not have to compute the build list and whether it's
running in GOPATH mode or module mode becomes irrelevant.
2021-02-15 16:45:26 -05:00

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SUBROUTINE AHCON (SIZE,N,M,A,B,OLEVR,OLEVI,CLEVR,CLEVI, TRUNCATED
& SCR1,SCR2,IPVT,JPVT,CON,WORK,ISEED,IERR) !Test inline comment
C
C FUNCTION:
CF
CF Determines whether the pair (A,B) is controllable and flags
CF the eigenvalues corresponding to uncontrollable modes.
CF this ad-hoc controllability calculation uses a random matrix F
CF and computes whether eigenvalues move from A to the controlled
CF system A+B*F.
CF
C USAGE:
CU
CU CALL AHCON (SIZE,N,M,A,B,OLEVR,OLEVI,CLEVR,CLEVI,SCR1,SCR2,IPVT,
CU JPVT,CON,WORK,ISEED,IERR)
CU
CU since AHCON generates different random F matrices for each
CU call, as long as iseed is not re-initialized by the main
CU program, and since this code has the potential to be fooled
CU by extremely ill-conditioned problems, the cautious user
CU may wish to call it multiple times and rely, perhaps, on
CU a 2-of-3 vote. We believe, but have not proved, that any
CU errors this routine may produce are conservative--i.e., that
CU it may flag a controllable mode as uncontrollable, but
CU not vice-versa.
CU
C INPUTS:
CI
CI SIZE integer - first dimension of all 2-d arrays.
CI
CI N integer - number of states.
CI
CI M integer - number of inputs.
CI
CI A double precision - SIZE by N array containing the
CI N by N system dynamics matrix A.
CI
CI B double precision - SIZE by M array containing the
CI N by M system input matrix B.
CI
CI ISEED initial seed for random number generator; if ISEED=0,
CI then AHCON will set ISEED to a legal value.
CI
C OUTPUTS:
CO
CO OLEVR double precision - N dimensional vector containing the
CO real parts of the eigenvalues of A.
CO
CO OLEVI double precision - N dimensional vector containing the
CO imaginary parts of the eigenvalues of A.
CO
CO CLEVR double precision - N dimensional vector work space
CO containing the real parts of the eigenvalues of A+B*F,
CO where F is the random matrix.
CO
CO CLEVI double precision - N dimensional vector work space
CO containing the imaginary parts of the eigenvalues of
CO A+B*F, where F is the random matrix.
CO
CO SCR1 double precision - N dimensional vector containing the
CO magnitudes of the corresponding eigenvalues of A.
CO
CO SCR2 double precision - N dimensional vector containing the
CO damping factors of the corresponding eigenvalues of A.
CO
CO IPVT integer - N dimensional vector; contains the row pivots
CO used in finding the nearest neighbor eigenvalues between
CO those of A and of A+B*F. The IPVT(1)th eigenvalue of
CO A and the JPVT(1)th eigenvalue of A+B*F are the closest
CO pair.
CO
CO JPVT integer - N dimensional vector; contains the column
CO pivots used in finding the nearest neighbor eigenvalues;
CO see IPVT.
CO
CO CON logical - N dimensional vector; flagging the uncontrollable
CO modes of the system. CON(I)=.TRUE. implies the
CO eigenvalue of A given by DCMPLX(OLEVR(IPVT(I)),OLEVI(IPVT(i)))
CO corresponds to a controllable mode; CON(I)=.FALSE.
CO implies an uncontrollable mode for that eigenvalue.
CO
CO WORK double precision - SIZE by N dimensional array containing
CO an N by N matrix. WORK(I,J) is the distance between
CO the open loop eigenvalue given by DCMPLX(OLEVR(I),OLEVI(I))
CO and the closed loop eigenvalue of A+B*F given by
CO DCMPLX(CLEVR(J),CLEVI(J)).
CO
CO IERR integer - IERR=0 indicates normal return; a non-zero
CO value indicates trouble in the eigenvalue calculation.
CO see the EISPACK and EIGEN documentation for details.
CO
C ALGORITHM:
CA
CA Calculate eigenvalues of A and of A+B*F for a randomly
CA generated F, and see which ones change. Use a full pivot
CA search through a matrix of euclidean distance measures
CA between each pair of eigenvalues from (A,A+BF) to
CA determine the closest pairs.
CA
C MACHINE DEPENDENCIES:
CM
CM NONE
CM
C HISTORY:
CH
CH written by: Birdwell & Laub
CH date: May 18, 1985
CH current version: 1.0
CH modifications: made machine independent and modified for
CH f77:bb:8-86.
CH changed cmplx -> dcmplx: 7/27/88 jdb
CH
C ROUTINES CALLED:
CC
CC EIGEN,RAND
CC
C COMMON MEMORY USED:
CM
CM none
CM
C----------------------------------------------------------------------
C written for: The CASCADE Project
C Oak Ridge National Laboratory
C U.S. Department of Energy
C contract number DE-AC05-840R21400
C subcontract number 37B-7685 S13
C organization: The University of Tennessee
C----------------------------------------------------------------------
C THIS SOFTWARE IS IN THE PUBLIC DOMAIN
C NO RESTRICTIONS ON ITS USE ARE IMPLIED
C----------------------------------------------------------------------
C
C--global variables:
C
INTEGER SIZE
INTEGER N
INTEGER M
INTEGER IPVT(1)
INTEGER JPVT(1)
INTEGER IERR
C
DOUBLE PRECISION A(SIZE,N)
DOUBLE PRECISION B(SIZE,M)
DOUBLE PRECISION WORK(SIZE,N)
DOUBLE PRECISION CLEVR(N)
DOUBLE PRECISION CLEVI(N)
DOUBLE PRECISION OLEVR(N)
DOUBLE PRECISION OLEVI(N)
DOUBLE PRECISION SCR1(N)
DOUBLE PRECISION SCR2(N)
C
LOGICAL CON(N)
C
C--local variables:
C
INTEGER ISEED
INTEGER ITEMP
INTEGER K1
INTEGER K2
INTEGER I
INTEGER J
INTEGER K
INTEGER IMAX
INTEGER JMAX
C
DOUBLE PRECISION VALUE
DOUBLE PRECISION EPS
DOUBLE PRECISION EPS1
DOUBLE PRECISION TEMP
DOUBLE PRECISION CURR
DOUBLE PRECISION ANORM
DOUBLE PRECISION BNORM
DOUBLE PRECISION COLNRM
DOUBLE PRECISION RNDMNO
C
DOUBLE COMPLEX DCMPLX
C
C--compute machine epsilon
C
EPS = 1.D0
100 CONTINUE
EPS = EPS / 2.D0
EPS1 = 1.D0 + EPS
IF (EPS1 .NE. 1.D0) GO TO 100
EPS = EPS * 2.D0
C
C--compute the l-1 norm of a
C
ANORM = 0.0D0
DO 120 J = 1, N
COLNRM = 0.D0
DO 110 I = 1, N
COLNRM = COLNRM + ABS(A(I,J))
110 CONTINUE
IF (COLNRM .GT. ANORM) ANORM = COLNRM
120 CONTINUE
C
C--compute the l-1 norm of b
C
BNORM = 0.0D0
DO 140 J = 1, M
COLNRM = 0.D0
DO 130 I = 1, N
COLNRM = COLNRM + ABS(B(I,J))
130 CONTINUE
IF (COLNRM .GT. BNORM) BNORM = COLNRM
140 CONTINUE
C
C--compute a + b * f
C
DO 160 J = 1, N
DO 150 I = 1, N
WORK(I,J) = A(I,J)
150 CONTINUE
160 CONTINUE
C
C--the elements of f are random with uniform distribution
C--from -anorm/bnorm to +anorm/bnorm
C--note that f is not explicitly stored as a matrix
C--pathalogical floating point notes: the if (bnorm .gt. 0.d0)
C--test should actually be if (bnorm .gt. dsmall), where dsmall
C--is the smallest representable number whose reciprocal does
C--not generate an overflow or loss of precision.
C
IF (ISEED .EQ. 0) ISEED = 86345823
IF (ANORM .EQ. 0.D0) ANORM = 1.D0
IF (BNORM .GT. 0.D0) THEN
TEMP = 2.D0 * ANORM / BNORM
ELSE
TEMP = 2.D0
END IF
DO 190 K = 1, M
DO 180 J = 1, N
CALL RAND(ISEED,ISEED,RNDMNO)
VALUE = (RNDMNO - 0.5D0) * TEMP
DO 170 I = 1, N
WORK(I,J) = WORK(I,J) + B(I,K)*VALUE
170 CONTINUE
180 CONTINUE
190 CONTINUE
C
C--compute the eigenvalues of a + b*f, and several other things
C
CALL EIGEN (0,SIZE,N,WORK,CLEVR,CLEVI,WORK,SCR1,SCR2,IERR)
IF (IERR .NE. 0) RETURN
C
C--copy a so it is not destroyed
C
DO 210 J = 1, N
DO 200 I = 1, N
WORK(I,J) = A(I,J)
200 CONTINUE
210 CONTINUE
C
C--compute the eigenvalues of a, and several other things
C
CALL EIGEN (0,SIZE,N,WORK,OLEVR,OLEVI,WORK,SCR1,SCR2,IERR)
IF (IERR .NE. 0) RETURN
C
C--form the matrix of distances between eigenvalues of a and
C--EIGENVALUES OF A+B*F
C
DO 230 J = 1, N
DO 220 I = 1, N
WORK(I,J) =
& ABS(DCMPLX(OLEVR(I),OLEVI(I))-DCMPLX(CLEVR(J),CLEVI(J)))
220 CONTINUE
230 CONTINUE
C
C--initialize row and column pivots
C
DO 240 I = 1, N
IPVT(I) = I
JPVT(I) = I
240 CONTINUE
C
C--a little bit messy to avoid swapping columns and
C--rows of work
C
DO 270 I = 1, N-1
C
C--find the minimum element of each lower right square
C--submatrix of work, for submatrices of size n x n
C--through 2 x 2
C
CURR = WORK(IPVT(I),JPVT(I))
IMAX = I
JMAX = I
TEMP = CURR
C
C--find the minimum element
C
DO 260 K1 = I, N
DO 250 K2 = I, N
IF (WORK(IPVT(K1),JPVT(K2)) .LT. TEMP) THEN
TEMP = WORK(IPVT(K1),JPVT(K2))
IMAX = K1
JMAX = K2
END IF
250 CONTINUE
260 CONTINUE
C
C--update row and column pivots for indirect addressing of work
C
ITEMP = IPVT(I)
IPVT(I) = IPVT(IMAX)
IPVT(IMAX) = ITEMP
C
ITEMP = JPVT(I)
JPVT(I) = JPVT(JMAX)
JPVT(JMAX) = ITEMP
C
C--do next submatrix
C
270 CONTINUE
C
C--this threshold for determining when an eigenvalue has
C--not moved, and is therefore uncontrollable, is critical,
C--and may require future changes with more experience.
C
EPS1 = SQRT(EPS)
C
C--for each eigenvalue pair, decide if it is controllable
C
DO 280 I = 1, N
C
C--note that we are working with the "pivoted" work matrix
C--and are looking at its diagonal elements
C
IF (WORK(IPVT(I),JPVT(I))/ANORM .LE. EPS1) THEN
CON(I) = .FALSE.
ELSE
CON(I) = .TRUE.
END IF
280 CONTINUE
C
C--finally!
C
RETURN
END
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