quad_qag(...) error message
- Subject: quad_qag(...) error message
- From: Edwin Woollett
- Date: Thu, 25 Sep 2008 13:40:26 -0700
I get quad_qag(..) error message no. 2
("excessive roundoff error") with
a very simple function f(x) = x.
---------------------------------
1. Why are we getting excessive
roundoff error with such a simple
integrand?
Or is this error message itself an error?
--------------------
2. Why are the SLATEC error messages
progressively disappearing the more
times we call quad_qags(..) with
the same function? ("message exhaustion")
===================
(%i1) integrate( x, x, -1, 1 );
(%o1) 0
/* quad_qag(..) run 1 */
(%i2) for i thru 6 do
(qlist : quad_qag( x, x, -1, 1, i ),
print( "key is ", i ," ", qlist ) )$
***MESSAGE FROM ROUTINE DQAG IN LIBRARY SLATEC.
***INFORMATIVE MESSAGE, PROG CONTINUES, TRACEBACK REQUESTED
* ABNORMAL RETURN
* ERROR NUMBER = 2
*
***END OF MESSAGE
key is 1 [0.0, 1.1020760842711039E-14, 15, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 2 [0.0, 1.1060840041517323E-14, 21, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 3 [0.0, 1.108321668765528E-14, 31, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 4 [0.0, 1.1091368685730577E-14, 41, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 5 [0.0, 1.1095211642996757E-14, 51, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 6 [0.0, 1.1097322727621492E-14, 61, 2]
-------------------
/* quad_qag(..) run 2 */
(%i3) for i thru 6 do
(qlist : quad_qag( x, x, -1, 1, i ),
print( "key is ", i ," ", qlist ) )$
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 1 [0.0, 1.1020760842711039E-14, 15, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 2 [0.0, 1.1060840041517323E-14, 21, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 3 [0.0, 1.108321668765528E-14, 31, 2]
[ SAME SLATEC MESSAGE, ERROR N0. 2 ]
key is 4 [0.0, 1.1091368685730577E-14, 41, 2]
key is 5 [0.0, 1.1095211642996757E-14, 51, 2]
key is 6 [0.0, 1.1097322727621492E-14, 61, 2]
--------------------
/* quad_qag(..) run 3 */
(%i4) for i thru 6 do
(qlist : quad_qag( x, x, -1, 1, i ),
print( "key is ", i ," ", qlist ) )$
key is 1 [0.0, 1.1020760842711039E-14, 15, 2]
key is 2 [0.0, 1.1060840041517323E-14, 21, 2]
key is 3 [0.0, 1.108321668765528E-14, 31, 2]
key is 4 [0.0, 1.1091368685730577E-14, 41, 2]
key is 5 [0.0, 1.1095211642996757E-14, 51, 2]
key is 6 [0.0, 1.1097322727621492E-14, 61, 2]
--------------------------
Ted Woollett