# [petsc-dev] coding style

Munson, Todd tmunson at mcs.anl.gov
Thu Aug 18 11:31:27 CDT 2016

```Here's the table.

In my opinion, the important cases are:

Constraints: box (e.g. l <= x <= u), polyhedral (e.g. l <= Ax + b <= u),
and general range (e.g. l <= F(x) <= u)

Variables: state, design

I am not a huge fan of separating into equality constraints and range constraints,
but we can keep it.  Having only equality constraints does make the problem much
easier to solve; no need to identify an active set.

The variable separation is needed for PDE constrained optimization.  We may want
to separate constraints into state constraints, design constraints, and
joint state/design constraints.  For now, I would only consider design
constraints.

In the future for stochastic problems, I would probably add a stochastic variable
type and some objective types (e.g. expectations) and constraints (e.g. chance or
probabilistic constraints).  That is further down the line though.

====

For separability, you can go down a complete rabbit hole of composite,
composition, separable, partially separable, group partially
separable, and all kinds of other things.

For TAO, I think we should keep it simple and restrict to structured
problems of the form:

f(x) = h(x) + g(F(x))

where h() and g() are selected from a menu of functions we provide
(e.g. one-norm, p-norm, two-norm, weighted two-norm) with well-defined
parameters supplied by the user (e.g. the weights) if necessary.

The user supplies F:R^n to R^m and derivatives.

I think this covers the main TAO codes that use such structure.
OWLQL, BMRM and POUNDerS.  Its also rich enough for new
methods people may want to add (e.g. Pareto surfaces
for multi-objective optimization).

Todd.

>   Before doing anything let's try to generate a table that includes all (most of?)  the cases.
>
>    The function being optimized is linear, quadratic, or general (another case is separable).
>
>    The equality constraints are linear?, quadratic? general?  or something else?
>
>     The inequality constraints are simple bounds? linear? quadratic? general? something else?
>
>     Is there a fourth (or even more) axis of problem properties?
>
>    Is this level of categories enough to organize the directories and naming of TAO solvers?
>
>  Barry
>
>
>
>>
>> The methods would then explicitly mention the type of optimization problem
>> with, for example, TAO_UCO_LMVM, TAO_BCO_TRON, and TAO_BQP_GPCG.
>>
>> Thoughts?
>>
>> Todd.
>>
>>
>>> On Aug 16, 2016, at 4:32 PM, Oxberry, Geoffrey Malcolm <oxberry1 at llnl.gov> wrote:
>>>
>>> Definitely flags for linear problems would be helpful for TAO. Once there is an example up, I'd be happy to add that to the SQPTR pull request.
>>>
>>> ________________________________________
>>> From: petsc-dev-bounces at mcs.anl.gov [petsc-dev-bounces at mcs.anl.gov] on behalf of Barry Smith [bsmith at mcs.anl.gov]
>>> Sent: Monday, August 15, 2016 6:18 PM
>>> To: Munson, Todd
>>> Cc: petsc-dev
>>> Subject: Re: [petsc-dev] coding style
>>>
>>>> On Aug 15, 2016, at 8:08 PM, Munson, Todd <tmunson at mcs.anl.gov> wrote:
>>>>
>>>>
>>>> Since we are only doing diagonal modifications to the matrix in
>>>> my case, should I simply create a matnest in my part of the
>>>> code and apply the diagonal modification in the matnest
>>>> without directly modifying any of the matrices?
>>>> That might be cleaner for the users.
>>>
>>> It will be dependent on the solver how much of the matrix you need retain the parts you have modified.
>>>
>>> MatNest isn't the right thing here. I think you can do MatGetDiagonal() to keep the valid diagonal entries then MatDiagonalSet() to put back the valid entries.
>>>
>>> Barry
>>>
>>>
>>>>
>>>> Todd.
>>>>
>>>>> On Aug 15, 2016, at 7:55 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>>>
>>>>>
>>>>>> On Aug 15, 2016, at 7:42 PM, Munson, Todd <tmunson at mcs.anl.gov> wrote:
>>>>>>
>>>>>>
>>>>>> Got it.  I will get all the code fragments in the developer doc that
>>>>>> are not meant to be deliberately wrong fixed tomorrow; at least
>>>>>> that code will be compliant...  :)
>>>>>>
>>>>>> Then its onto fixing bqpip.
>>>>>>
>>>>>> Was there a final say on the Hessian/Jacobian matrix when they are
>>>>>> modified?  Were we adding a "dirty" bit or was I changing my code
>>>>>> to not modify those matrices?
>>>>>
>>>>> Changing email to petsc-dev since this is a general PETSc/TAO issue.
>>>>>
>>>>> This is why we don't wait months to fix something :-) I have completely forgot the context you are asking  about.
>>>>>
>>>>> I think the general issue comes up when a problem is linear and the user just wants to set and forget the matrices while when the problem is nonlinear the user needs to reset values into the matrix anyways so it is fine for you to change the matrix internally. Unless there is a way for the user to explicitly indicate the system is linear your code cannot know if it needs to make a copy of the matrix.
>>>>>
>>>>> In TS we have typedef enum {TS_LINEAR,TS_NONLINEAR} TSProblemType; and TSSetProblemType() that can be used to indicate if the matrices can be changed or not (though I don't think we use it in this way, we have an open issue https://bitbucket.org/petsc/petsc/issues/135/memory-optimization-for-ts
>>>>>
>>>>> I think you should start by having a flag that indicates if it is safe to modify the matrices associated with the TAO object and if not safe keep a backup copy.
>>>>>
>>>>> Barry
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> Todd.
>>>>>>
>>>>>>> On Aug 15, 2016, at 6:09 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>>>>>>
>>>>>>>
>>>>>>> Todd,
>>>>>>>
>>>>>>>> On Aug 15, 2016, at 10:26 AM, Satish Balay <balay at mcs.anl.gov> wrote:
>>>>>>>>
>>>>>>>> Todd,
>>>>>>>>
>>>>>>>> Forwarding this to Barry.
>>>>>>>>
>>>>>>>> Satish
>>>>>>>>
>>>>>>>> On Mon, 15 Aug 2016, Munson, Todd wrote:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> I'm going through the developer documentation.  There seems to be
>>>>>>>>> a few things missing from the coding style.
>>>>>>>>>
>>>>>>>>> For example, in function prototypes, is it:
>>>>>>>>>
>>>>>>>>> PetscErrorCode MyFunction(char *,const int *,int);
>>>>>>>>>
>>>>>>>>> or
>>>>>>>>>
>>>>>>>>> PetscErrorCode MyFunction(char*,const int*,int)
>>>>>>>
>>>>>>> The second one because the preference is to not have unnecessary space.
>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Same thing in the definitions:
>>>>>>>>>
>>>>>>>>> PetscErrorCode MyFunction(char *c,const int *i,int j)
>>>>>>>>> {
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> or
>>>>>>>>>
>>>>>>>>> PetscErrorCode MyFunction(char* c,const int* i,int j)
>>>>>>>
>>>>>>> The * should always be attached to the variable.
>>>>>>>>> {
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> The same questions apply with * replaced by [].
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Next is in the types for variables.  Are pointers grouped
>>>>>>>>> separately or together with the type:
>>>>>>>>>
>>>>>>>>> int   *i,j,*k;
>>>>>>>>>
>>>>>>>>> or
>>>>>>>>>
>>>>>>>>> int   *i,*k;
>>>>>>>>> int   j;
>>>>>>>>>
>>>>>>>>> If grouped together, should they be ordered with pointers first
>>>>>>>>> and the others later?
>>>>>>>>>
>>>>>>>>> int   *i,*k,j;
>>>>>>>
>>>>>>> There is no preference on the above; the pointers do not have to be on their own line.
>>>>>>>>>
>>>>>>>>> On the next topic, do you use
>>>>>>>>>
>>>>>>>>> char    *blah;
>>>>>>>>>
>>>>>>>>> or
>>>>>>>>>
>>>>>>>>> char*   blah;
>>>>>>>>>
>>>>>>>>> when there is only one of them?
>>>>>>>
>>>>>>> * belongs on the variable
>>>>>>>
>>>>>>>>>
>>>>>>>>> I have the same issues with the typedefs.  Sometimes there is
>>>>>>>>>
>>>>>>>>> typedef struct _EH* EH;
>>>>>>>>>
>>>>>>>>> and other times
>>>>>>>>>
>>>>>>>>> typedef struct _EH *EH;
>>>>>>>
>>>>>>> Here the * belongs as in the first case
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> My personal thought is to be consistent and use char * with a space
>>>>>>>>> everywhere, but you tell me.  I will then go and fix the developer
>>>>>>>>> documentation to be consistent with the style guide as a test of
>>>>>>>>> my branch management.
>>>>>>>>>
>>>>>>>>> Todd.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

```