share/colnew/fortran/shiftb.f

   1       SUBROUTINE SHIFTB (AI, NROWI, NCOLI, LAST, AI1, NROWI1, NCOLI1)
   2 C
   3 C*********************************************************************
   4 C
   5 C     shifts the rows in current block, ai, not used as pivot rows, if
   6 C     any, i.e., rows  (last+1),..., (nrowi), onto the first mmax =
   7 C      = nrow-last  rows of the next block, ai1, with column last+j of
   8 C      ai  going to column j , j=1,...,jmax=ncoli-last. the remaining
   9 C     columns of these rows of ai1 are zeroed out.
  10 C
  11 C                                picture
  12 C
  13 C          original situation after         results in a new block i+1
  14 C          last = 2 columns have been       created and ready to be
  15 C          done in factrb (assuming no      factored by next factrb
  16 C          interchanges of rows)            call.
  17 C                      1
  18 C                 x  x 1x  x  x           x  x  x  x  x
  19 C                      1
  20 C                 0  x 1x  x  x           0  x  x  x  x
  21 C     block i          1                       ---------------
  22 C     nrowi = 4   0  0 1x  x  x           0  0 1x  x  x  0  01
  23 C     ncoli = 5        1                       1             1
  24 C     last = 2    0  0 1x  x  x           0  0 1x  x  x  0  01
  25 C     -------------------------------          1             1   new
  26 C                      1x  x  x  x  x          1x  x  x  x  x1  block
  27 C                      1                       1             1   i+1
  28 C     block i+1        1x  x  x  x  x          1x  x  x  x  x1
  29 C     nrowi1= 5        1                       1             1
  30 C     ncoli1= 5        1x  x  x  x  x          1x  x  x  x  x1
  31 C     -------------------------------          1-------------1
  32 C                      1
  33 C
  34 C*********************************************************************
  35 C
  36       INTEGER LAST, J,JMAX,JMAXP1,M,MMAX
  37       DOUBLE PRECISION AI(NROWI,NCOLI),AI1(NROWI1,NCOLI1)
  38       MMAX = NROWI - LAST
  39       JMAX = NCOLI - LAST
  40       IF (MMAX .LT. 1 .OR. JMAX .LT. 1)             RETURN
  41 C
  42 C...  put the remainder of block i into ai1
  43 C
  44       DO 10 J=1,JMAX
  45            DO 10 M=1,MMAX
  46    10 AI1(M,J) = AI(LAST+M,LAST+J)
  47       IF (JMAX .EQ. NCOLI1)                         RETURN
  48 C
  49 C...  zero out the upper right corner of ai1
  50 C
  51       JMAXP1 = JMAX + 1
  52       DO 20 J=JMAXP1,NCOLI1
  53            DO 20 M=1,MMAX
  54    20 AI1(M,J) = 0.D0
  55       RETURN
  56       END