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Library functions and the programming interface

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Counting

All Xpress-SLP entities are numbered from 1. The 0^th item is defined, and is an empty entity of the appropriate type. Therefore, whenever an Xpress-SLP function returns a zero value, it means that there is no data of that type.

In parsed and unparsed function arrays, the indices always count from 1. This includes types XSLP_VAR and XSLP_CONSTRAINT: the index is the matrix column or row index + XPRS_CSTYLE.

Note that for input of function arrays, types XSLP_COL and XSLP_ROW can be used; these do honor the setting of XPRS_CSTYLE, but will be converted into standard XSLP_VAR or XSLP_CONSTRAINT references. When a function array is returned from Xpress-SLP, the XSLP_VAR or XSLP_CONSTRAINT type will always be used.

Matrix row and column indices do honor the setting of XPRS_CSTYLE: that is, they count from zero if XPRS_CSTYLE=1, and from 1 if XPRS_CSTYLE=0.

Xpress-SLP functions affected by XPRS_CSTYLE

Function	Arguments affected
XSLPaddcoefs	RowIndex, ColIndex
XSLPadddcs	RowIndex
XSLPaddvars	ColIndex, DetRow
XSLPchgccoef	RowIndex, ColIndex
XSLPchgcoef	RowIndex, ColIndex
XSLPchgdc	RowIndex
XSLPchgrow	RowIndex
XSLPchgvar	ColIndex, DetRow
XSLPevaluatecoef	RowIndex, ColIndex
XSLPgetccoef	RowIndex, ColIndex
XSLPgetcoef	RowIndex, ColIndex
XSLPgetdc	RowIndex
XSLPgetrow	RowIndex
XSLPgetvar	ColIndex, DetRow, Delta, PenaltyDelta, UpdateRow
XSLPloadcoefs	RowIndex, ColIndex
XSLPloaddcs	RowIndex
XSLPloadvars	ColIndex, DetRow
also user callbacks defined by:
XSLPsetcbcascadevar	ColIndex
XSLPsetcbitervar	ColIndex
and all functions which have arguments which are indices into arrays.

The Xpress-SLP problem pointer

Xpress-SLP uses the same concept as the Optimizer library, with a "pointer to a problem". The optimizer problem must be initialized first in the normal way. Then the corresponding Xpress-SLP problem must be initialized, including a pointer to the underlying optimizer problem. For example:

{
	...
	XPRSprob prob=NULL;
	XSLPprob SLPprob=NULL;

	XPRSinit("");
	XSLPinit();
	XPRScreateprob(&prob);
	XSLPcreateprob(&SLPprob,&prob);
	...
}

At the end of the program, the Xpress-SLP problem should be destroyed. You are responsible for destroying the underlying XPRSprob linear problem afterwards. For example:

{
...
  XSLPdestroyprob(SLPprob);
  XPRSdestroyprob(prob);
  XSLPfree();
  XPRSfree();
  ...
}

The following functions are provided to manage Xpress-SLP problems. See the documentation below on the individual functions for more details.

XSLPcopycontrols(XSLPprob prob1, XSLPprob prob2)
   Copy the settings of control variables

XSLPcopycallbacks(XSLPprob prob1, XSLPprob prob2)
   Copy the callback settings

XSLPcopyprob(XSLPprob prob1, XSLPprob prob2, char *ProbName)
   Copy a problem completely

XSLPcreateprob(XSLPprob *prob1, XPRSprob *prob2)
   Create an Xpress-SLP problem

XSLPdestroyprob(XSLPprob prob1)
   Delete an Xpress-SLP problem from memory

XSLPrestore(XSLPprob prob1)
   Restore Xpress-SLP data structures from file

XSLPsave(XSLPprob prob1)
   Save Xpress-SLP data structures to file

The XSLPload... functions

The XSLPload... functions can be used to load an Xpress-SLP problem directly into the Xpress data structures. Because there are so many additional items which can be loaded apart from the basic (linear) matrix, the loading process is divided into several functions.

The linear part of the problem should be loaded first, using the normal Optimizer Library functions XPRSloadlp or XPRSloadglobal. Then the appropriate parts of the Xpress-SLP problem can be loaded. After all the XSLPload... functions have been called, XSLPconstruct should be called to create the SLP matrix and data structures. If XSLPconstruct is not invoked before a call to one of the Xpress-SLP optimization routines, then it will be called by the optimization routine itself.

All of these functions initialize their data areas. Therefore, if a second call is made to the same function for the same problem, the previous data will be deleted. If you want to include additional data of the same type, then use the corresponding XSLPadd... function.

Xpress-SLP is compatible with the Xpress quadratic programming optimizer. XPRSloadqp and XPRSloadqglobal can be used to load quadratic problems. The quadratic objective will be optimized using the Xpress quadratic optimizer; the nonlinear constraints will be handled with the normal SLP procedures.

Library functions

A large number of routines are available for Library users of Xpress-SLP, ranging from simple routines for the input and solution of problems from matrix files to sophisticated callback functions and greater control over the solution process. Library users have access to a set of functions providing advanced control over their program's interaction with the SLP module and catering for more complicated problem development.

XSLPaddcoefs	Add non-linear coefficients to the SLP problem
XSLPaddcvars	Add character variables (CVs) to the SLP problem
XSLPadddcs	Add delayed constraints (DCs) to the SLP problem
XSLPaddnames	Set the names of a set of SLP entities in an SLP problem.
XSLPaddtolsets	Add sets of standard tolerance values to an SLP problem
XSLPadduserfuncs	Add user function definitions to an SLP problem.
XSLPaddvars	Add SLP variables defined as matrix columns to an SLP problem
XSLPaddxvs	Add a set of extended variable arrays (XVs) to an SLP problem
XSLPcalluserfunc	Call a user function from a program or from within another user function
XSLPcascade	Re-calculate consistent values for SLP variables. based on the current values of the remaining variables
XSLPcascadeorder	Establish a re-calculation sequence for SLP variables with determining rows.
XSLPchgccoef	Add or change a single matrix coefficient using a character string for the formula
XSLPchgcoef	Add or change a single matrix coefficient using a parsed or unparsed formula
XSLPchgcvar	Add or change the value of the character string corresponding to an SLP character variable
XSLPchgdc	Add or change the settings for a delayed constraint (DC)
XSLPchgfuncobject	Change the address of one of the objects which can be accessed by the user functions
XSLPchgrow	Change the status setting of a constraint
XSLPchgtolset	Add or change a set of convergence tolerances used for SLP variables
XSLPchguserfunc	Add or change a user function in an SLP problem after the problem has been input
XSLPchguserfuncaddress	Change the address of a user function
XSLPchguserfuncobject	Change or define one of the objects which can be accessed by the user functions
XSLPchgvar	Define a column as an SLP variable or change the characteristics and values of an existing SLP variable
XSLPchgxv	Add or change an extended variable array (XV) in an SLP problem
XSLPchgxvitem	Add or change an item of an existing XV in an SLP problem
XSLPconstruct	Create the full augmented SLP matrix and data structures, ready for optimization
XSLPcopycallbacks	Copy the user-defined callbacks from one SLP problem to another
XSLPcopycontrols	Copy the values of the control variables from one SLP problem to another
XSLPcopyprob	Copy an existing SLP problem to another
XSLPcreateprob	Create a new SLP problem
XSLPdestroyprob	Delete an SLP problem and release all the associated memory
XSLPevaluatecoef	Evaluate a coefficient using the current values of the variables
XSLPevaluateformula	Evaluate a formula using the current values of the variables
XSLPformatvalue	Format a double-precision value in the style of Xpress-SLP
XSLPfree	Free any memory allocated by Xpress-SLP and close any open Xpress-SLP files
XSLPgetbanner	Retrieve the Xpress-SLP banner and copyright messages
XSLPgetccoef	Retrieve a single matrix coefficient as a formula in a character string
XSLPgetcoef	Retrieve a single matrix coefficient as a formula split into tokens
XSLPgetcvar	Retrieve the value of the character string corresponding to an SLP character variable
XSLPgetdblattrib	Retrieve the value of a double precision problem attribute
XSLPgetdblcontrol	Retrieve the value of a double precision problem control
XSLPgetdc	Retrieve information about a delayed constraint in an SLP problem
XSLPgetdtime	Retrieve a double precision time stamp in seconds
XSLPgetfuncinfo	Retrieve the argument information for a user function
XSLPgetfuncinfoV	Retrieve the argument information for a user function
XSLPgetfuncobject	Retrieve the address of one of the objects which can be accessed by the user functions
XSLPgetfuncobjectV	Retrieve the address of one of the objects which can be accessed by the user functions
XSLPgetindex	Retrieve the index of an Xpress-SLP entity with a given name
XSLPgetintattrib	Retrieve the value of an integer problem attribute
XSLPgetintcontrol	Retrieve the value of an integer problem control
XSLPgetlasterror	Retrieve the error message corresponding to the last Xpress-SLP error during an SLP run
XSLPgetmessagetype	Retrieve the message type corresponding to a message number
XSLPgetnames	Retrieve the names of a set of Xpress-SLP entities
XSLPgetparam	Retrieve the value of a control parameter or attribute by name
XSLPgetptrattrib	Retrieve the value of a problem pointer attribute
XSLPgetrow	Retrieve the status setting of a constraint
XSLPgetslpsol	Obtain the solution values for the most recent SLP iteration
XSLPgetstrattrib	Retrieve the value of a string problem attribute
XSLPgetstrcontrol	Retrieve the value of a string problem control
XSLPgetstring	Retrieve the value of a string in the Xpress-SLP string table
XSLPgettime	Retrieve an integer time stamp in seconds and/or milliseconds
XSLPgettolset	Retrieve the values of a set of convergence tolerances for an SLP problem
XSLPgetuserfunc	Retrieve the type and parameters for a user function
XSLPgetuserfuncaddress	Retrieve the address of a user function
XSLPgetuserfuncobject	Retrieve the address of one of the objects which can be accessed by the user functions
XSLPgetvar	Retrieve information about an SLP variable
XSLPgetversion	Retrieve the Xpress-SLP major and minor version numbers
XSLPgetxv	Retrieve information about an extended variable array
XSLPgetxvitem	Retrieve information about an item in an extended variable array
XSLPglobal	Initiate the Xpress-SLP mixed integer SLP (MISLP) algorithm
XSLPinit	Initializes the Xpress-SLP system
XSLPitemname	Retrieves the name of an Xpress-SLP entity or the value of a function token as a character string.
XSLPloadcoefs	Load non-linear coefficients into the SLP problem
XSLPloadcvars	Load character variables (CVs) into the SLP problem
XSLPloaddcs	Load delayed constraints (DCs) into the SLP problem
XSLPloadtolsets	Load sets of standard tolerance values into an SLP problem
XSLPloaduserfuncs	Load user function definitions into an SLP problem.
XSLPloadvars	Load SLP variables defined as matrix columns into an SLP problem
XSLPloadxvs	Load a set of extended variable arrays (XVs) into an SLP problem
XSLPmaxim	Maximize an SLP problem
XSLPminim	Minimize an SLP problem
XSLPopt	Maximize or minimize an SLP problem
XSLPparsecformula	Parse a formula written as a character string into internal parsed (reverse Polish) format
XSLPparseformula	Parse a formula written as an unparsed array of tokens into internal parsed (reverse Polish) format
XSLPpreparseformula	Perform an initial scan of a formula written as a character string, identifying the operators but not attempting to identify the types of the individual tokens
XSLPpresolve	Perform a nonlinear presolve on the problem
XSLPprintmsg	Print a message string according to the current settings for Xpress-SLP output
XSLPqparse	Perform a quick parse on a free-format character string, identifying where each token starts
XSLPreadprob	Read an Xpress-SLP extended MPS format matrix from a file into an SLP problem
XSLPremaxim	Continue the maximization of an SLP problem
XSLPreminim	Continue the minimization of an SLP problem
XSLPrestore	Restore the Xpress-SLP problem from a file created by XSLPsave
XSLPrevise	Revise the unaugmented SLP matrix with data from a file
XSLPsave	Save the Xpress-SLP problem to file
XSLPsaveas	Save the Xpress-SLP problem to a named file
XSLPscaling	Analyze the current matrix for largest/smallest coefficients and ratios
XSLPsetcbcascadeend	Set a user callback to be called at the end of the cascading process, after the last variable has been cascaded
XSLPsetcbcascadestart	Set a user callback to be called at the start of the cascading process, before any variables have been cascaded
XSLPsetcbcascadevar	Set a user callback to be called after each column has been cascaded
XSLPsetcbcascadevarF	Set a user callback to be called after each column has been cascaded
XSLPsetcbdestroy	Set a user callback to be called when an SLP problem is about to be destroyed
XSLPsetcbintsol	Set a user callback to be called during MISLP when an integer solution is obtained
XSLPsetcbiterend	Set a user callback to be called at the end of each SLP iteration
XSLPsetcbiterstart	Set a user callback to be called at the start of each SLP iteration
XSLPsetcbitervar	Set a user callback to be called after each column has been tested for convergence
XSLPsetcbitervarF	Set a user callback to be called after each column has been tested for convergence
XSLPsetcbmessage	Set a user callback to be called whenever Xpress-SLP outputs a line of text
XSLPsetcbmessageF	Set a user callback to be called whenever Xpress-SLP outputs a line of text
XSLPsetcboptnode	Set a user callback to be called during MISLP when an optimal SLP solution is obtained at a node
XSLPsetcbprenode	Set a user callback to be called during MISLP after the set-up of the SLP problem to be solved at a node, but before SLP optimization
XSLPsetcbslpend	Set a user callback to be called at the end of the SLP optimization
XSLPsetcbslpnode	Set a user callback to be called during MISLP after the SLP optimization at each node.
XSLPsetcbslpstart	Set a user callback to be called at the start of the SLP optimization
XSLPsetdblcontrol	Set the value of a double precision problem control
XSLPsetdefaultcontrol	Set the values of one SLP control to its default value
XSLPsetdefaults	Set the values of all SLP controls to their default values
XSLPsetfuncobject	Change the address of one of the objects which can be accessed by the user functions
XSLPsetfunctionerror	Set the function error flag for the problem
XSLPsetintcontrol	Set the value of an integer problem control
XSLPsetlogfile	Define an output file to be used to receive messages from Xpress-SLP
XSLPsetparam	Set the value of a control parameter by name
XSLPsetstrcontrol	Set the value of a string problem control
XSLPsetstring	Set a value in the Xpress-SLP string table
XSLPsetuniqueprefix	Find a prefix character string which is different from all the names currently in use within the SLP problem
XSLPsetuserfuncaddress	Change the address of a user function
XSLPsetuserfuncinfo	Set up the argument information array for a user function call
XSLPsetuserfuncobject	Set or define one of the objects which can be accessed by the user functions
XSLPtime	Print the current date and time
XSLPtokencount	Count the number of tokens in a free-format character string
XSLPtoVBString	Return a string to VB given its address in Xpress-SLP
XSLPuprintmemory	Print the dimensions and memory allocations for a problem
XSLPvalidate	Validate the feasibility of constraints in a converged solution
XSLPvalidformula	Check a formula in internal (parsed or unparsed) format for unknown tokens
XSLPwriteprob	Write the current problem to a file in extended MPS or text format

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