+--------------------------------------------------------------------+
| |
| ADVAN7: FACTOR |
| |
+--------------------------------------------------------------------+
MEANING: PREDPP global variables
CONTEXT: For use with PREDPP
USAGE:
$PK
"FIRST
" USE PRCOM_REAL, ONLY: FACTOR=>FAC
"MAIN
" FACTOR=10.
GLOBAL DECLARATION:
USE SIZES, ONLY: DPSIZE
REAL(KIND=DPSIZE) :: FAC
DISCUSSION:
This feature is not fully documented. The interested user may be able
to obtain more information by studying the appropriate sections of
PREDPP code.
USAGE:
A message similar to the following is sometimes produced by ADVAN7:
NUMERICAL DIFFICULTIES OBTAINING THE SOLUTION. NON-REAL
EIGENVALUES. PERHAPS ADVAN5 SHOULD BE USED FOR THIS PROBLEM.
"LARGEST" VALUE ALONG SUBDIAGONAL OF SCHUR MATRIX: 0.423E-01
(DIAG: 0.84E+00 0.84E+00)
FACTOR is a "fudge factor" that affects ADVAN7's determination of how
large the subdiagonal element is relative to the two diagonal ele-
ments. The default value of FACTOR is 1.
These error messages arise when the computations of the eigenvalues
produce unexpected values. The question is whether the subdiagonal
elements are too large to ignore (e.g., when the eigenvalues are truly
complex) in which case ADVAN5 must be used, or whether trivially small
quantities have been produced by the accumulation of rounding error in
the floating point computation, in which ADVAN7 can be used. (Non-
real eigenvalues result when the system is non-mamillary, and may also
occasionally occur when there are etas associated with rate constants
Kij).
If the maximum value printed is very small (e.g., E-15), then the com-
putations will proceed correctly using a value of FACTOR such as 10 or
100. Values such as FACTOR=10 or FACTOR=100 are more permissive, and
allow larger subdiagonal elements. If no reasonable value of FACTOR
eliminates the error messages, then ADVAN5 should be used.
Location prior to NONMEM 7: prcomw
REFERENCES: None.
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