GALAHAD gls package

purpose

The gls package solves sparse unsymmetric systems of linear equations using a variant of Gaussian elimination. Given a sparse symmetric matrix \(A = \{ a_{ij} \}_{m \times n}\), and an \(n\)-vector \(b\), this function solves the system \(A x = b\). If instead \(b\) is an \(m\)-vector, the function may solve instead \(A^T x = b\). gls is based upon a modern fortran interface to the HSL Archive fortran 77 package MA28, which itself relies on MA33. To obtain HSL Archive packages, see

• http://hsl.rl.ac.uk/archive/ .

Currently only the options and info dictionaries are exposed; these are provided and used by other GALAHAD packages with Python interfaces. Extended functionality is available with the uls function.

See Section 4 of $GALAHAD/doc/gls.pdf for a brief description of the method employed and other details.

callable functions

overview of functions provided

// typedefs

typedef float spc_;
typedef double rpc_;
typedef int ipc_;

// structs

struct gls_ainfo_type;
struct gls_control_type;
struct gls_finfo_type;
struct gls_sinfo_type;

// global functions

void gls_initialize(void **data, struct gls_control_type* control);
void gls_read_specfile(struct gls_control_type* control, const char specfile[]);
void gls_import(struct gls_control_type* control, void **data, ipc_ *status);
void gls_reset_control(struct gls_control_type* control, void **data, ipc_ *status);

void gls_information(
    void **data,
    struct gls_ainfo_type* ainfo,
    struct gls_finfo_type* finfo,
    struct gls_sinfo_type* sinfo,
    ipc_ *status
);

void gls_finalize(void **data, struct gls_contro_typel* control, ipc_ *status);

typedefs

typedef float spc_

spc_ is real single precision

typedef double rpc_

rpc_ is the real working precision used, but may be changed to float by defining the preprocessor variable REAL_32 or (if supported) to __real128 using the variable REAL_128.

typedef int ipc_

ipc_ is the default integer word length used, but may be changed to int64_t by defining the preprocessor variable INTEGER_64.

function calls

void gls_initialize(void **data, struct gls_control_type* control)

Set default control values and initialize private data

Parameters:

data	holds private internal data
control	is a struct containing control information (see gls_control_type)

void gls_read_specfile(struct gls_control_type* control, const char specfile[])

Read the content of a specification file, and assign values associated with given keywords to the corresponding control parameters. An in-depth discussion of specification files is available, and a detailed list of keywords with associated default values is provided in $GALAHAD/src/gls/GLS.template. See also Table 2.1 in the Fortran documentation provided in $GALAHAD/doc/gls.pdf for a list of how these keywords relate to the components of the control structure.

Parameters:

control	is a struct containing control information (see gls_control_type)
specfile	is a character string containing the name of the specification file

void gls_import(struct gls_control_type* control, void **data, ipc_ *status)

Import problem data into internal storage prior to solution.

Parameters:

control	is a struct whose members provide control paramters for the remaining prcedures (see gls_control_type)
data	holds private internal data
status	is a scalar variable of type ipc_, that gives the exit status from the package. Possible values are: 1 The import was successful, and the package is ready for the solve phase -1 An allocation error occurred. A message indicating the offending array is written on unit control.error, and the returned allocation status and a string containing the name of the offending array are held in inform.alloc_status and inform.bad_alloc respectively. -2 A deallocation error occurred. A message indicating the offending array is written on unit control.error and the returned allocation status and a string containing the name of the offending array are held in inform.alloc_status and inform.bad_alloc respectively. -3 The restriction n > 0 or requirement that type contains its relevant string ‘dense’, ‘coordinate’, ‘sparse_by_rows’, ‘diagonal’ or ‘absent’ has been violated.

void gls_reset_control(struct gls_control_type* control, void **data, ipc_ *status)

Reset control parameters after import if required.

Parameters:

control	is a struct whose members provide control paramters for the remaining prcedures (see gls_control_type)
data	holds private internal data
status	is a scalar variable of type ipc_, that gives the exit status from the package. Possible values are: 1 The import was successful, and the package is ready for the solve phase

void gls_information(
    void **data,
    struct gls_ainfo_type* ainfo,
    struct gls_finfo_type* finfo,
    struct gls_sinfo_type* sinfo,
    ipc_ *status
)

Provides output information

Parameters:

data	holds private internal data
ainfo	is a struct containing analysis output information (see gls_ainfo_type)
finfo	is a struct containing factorization output information (see gls_finfo_type)
sinfo	is a struct containing solver output information (see gls_sinfo_type)
status	is a scalar variable of type ipc_, that gives the exit status from the package. Possible values are (currently): The values were recorded successfully

void gls_finalize(void **data, struct gls_control_type* control, ipc_ *status)

Deallocate all internal private storage

Parameters:

data	holds private internal data
control	is a struct containing control information (see gls_control_type)
status	is a scalar variable of type ipc_, that gives the exit status from the package. Possible values are (currently): 0 The values were recorded successfully

available structures

Index