* Jacobian matrix and the Null pointer
@ 2003-08-06 2:05 Haisam K. Ido
2003-08-07 18:01 ` Brian Gough
0 siblings, 1 reply; 2+ messages in thread
From: Haisam K. Ido @ 2003-08-06 2:05 UTC (permalink / raw)
To: gsl-discuss
What is the null pointer in the text below?
ref: http://sources.redhat.com/gsl/ref/gsl-ref_25.html#SEC379
"... int (* jacobian) (double t, const double y[], double * dfdy, double dfdt[],
void * params);
This function should store the vector elements df_i(t,y,params)/dt in the array
dfdt and the Jacobian matrix J_{ij} in the array dfdy regarded as a row-ordered
matrix J(i,j) = dfdy[i * dim + j] where dim is the dimension of the system. Some of
the simpler solver algorithms do not make use of the Jacobian matrix, so it is not
always strictly necessary to provide it (this element of the struct can be replace
by a *null pointer*). However, it is useful to provide the Jacobian to allow the
solver ...."
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Jacobian matrix and the Null pointer
2003-08-06 2:05 Jacobian matrix and the Null pointer Haisam K. Ido
@ 2003-08-07 18:01 ` Brian Gough
0 siblings, 0 replies; 2+ messages in thread
From: Brian Gough @ 2003-08-07 18:01 UTC (permalink / raw)
To: Haisam K. Ido; +Cc: gsl-discuss
Haisam K. Ido writes:
> What is the null pointer in the text below?
>
> ref: http://sources.redhat.com/gsl/ref/gsl-ref_25.html#SEC379
There should be an explanation of what null pointers are in any
introductory book on C.
regards
--
Brian Gough
Network Theory Ltd
15 Royal Park
Bristol BS8 3AL
United Kingdom
Tel: +44 (0)117 3179309
Fax: +44 (0)117 9048108
Web: http://www.network-theory.co.uk/
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2003-08-06 2:05 Jacobian matrix and the Null pointer Haisam K. Ido
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