Context

Context

#include <sbio/core/context.hh>

template<IOTraits IO, class EPolicy>
class Context

Defined in src/lib/sbio/core/context.hh:92

The Context constructs DataSources from IO and Execution policies within an environment.

The Context provides a mechanism to check both the compatiblity of the various policies that are being composed (in large part at compile), as well as a central place to handle interactions with the environment.

The Context can record and interface directly with environment variables, which may be needed for locating streams e.g. (not yet implemented with Locator support), as well as various configuration of execution policies.

Compile time checks look for:

• IOCapability
• ParallelSupport

At construction runtime checks include:

• IO::validate_environment for the IO policy (if provided).
• Execution::validate_environment for the execution policy
  • E.g. to check MPI thread support level.

Context will only configure the EPolicy once. From the Context DataSources can be created (using a separate constructor that avoids reconfiguration).

Note

The Context only provides an alternative entry-point and a DataSource can still be created directly.

sbio::Context<sbio::SyncPOSIXIO, sbio::ThreadedExecution> ctx(ecfg);
if (!ctx.ok()) {
  std::cerr << ctx.error() << std::endl;
}
auto ds = ctx.data_source<sbio::XTC2Traits>();

Template Parameters

• IO The IO policy.

• EPolicy The Execution policy.

Public Methods

Return	Name	Description
	Context inline explicit	Validate the proposed policies within the environment and then configure.
	~Context inline
	Context	Deleted constructor.
Context &	operator=	Deleted assignment operator.
	Context	Deleted constructor.
Context &	operator=	Deleted assignment operator.
bool	ok const inline
const std::string &	error const inline
DataSource< IO, EPolicy, FTraits >	data_source const inline requires FormatTraits<FTraits, IO, EPolicy>	Construct a DataSource from the Context.
std::string	env const inline	Retrieve an environment variable, with optional fallback.
bool	has_env const inline
void	set_env inline	Provide a specific override for an environment variable that only the Context uses.

---

Context

inline explicit

inline explicit Context(const EPolicyConfig & config = {})

Defined in src/lib/sbio/core/context.hh:108

Validate the proposed policies within the environment and then configure.

Parameters

Parameter	Type	Description
config	const EPolicyConfig &	The Execution policy configuration.

---

~Context

inline

inline ~Context()

Defined in src/lib/sbio/core/context.hh:136

---

Context

Context(const Context &) = delete

Defined in src/lib/sbio/core/context.hh:148

Deleted constructor.

---

operator=

Context & operator=(const Context &) = delete

Defined in src/lib/sbio/core/context.hh:149

Deleted assignment operator.

---

Context

Context(Context &&) = delete

Defined in src/lib/sbio/core/context.hh:150

Deleted constructor.

---

operator=

Context & operator=(Context &&) = delete

Defined in src/lib/sbio/core/context.hh:151

Deleted assignment operator.

---

ok

const inline

inline bool ok() const

Defined in src/lib/sbio/core/context.hh:156

Returns

Whether the Context is valid (EPolicy has been configured.)

---

error

const inline

inline const std::string & error() const

Defined in src/lib/sbio/core/context.hh:161

Returns

Why the Context is not valid or empty string.

---

data_source

const inline requires FormatTraits<FTraits, IO, EPolicy>

template<class FTraits> inline DataSource< IO, EPolicy, FTraits > data_source() const requires FormatTraits<FTraits, IO, EPolicy>

Defined in src/lib/sbio/core/context.hh:242

Construct a DataSource from the Context.

Note

The DataSource will use the Context’s (configured) EPolicy and IOPolicy.

Preconditions

[ok()](#ok).

Returns

The DataSource, ready for stream locating.

---

env

const inline

inline std::string env(std::string_view key, std::string_view fallback = {}) const

Defined in src/lib/sbio/core/context.hh:258

Retrieve an environment variable, with optional fallback.

Note

The Context may also set overrides itself. These will be looked up before checking the actual process environment.

Returns

The value.

Parameters

Parameter	Type	Description
key	std::string_view	The environment variable name.
fallback	std::string_view	The value if the variable is not set.

---

has_env

const inline

inline bool has_env(std::string_view key) const

Defined in src/lib/sbio/core/context.hh:273

Returns

Whether key is set in the Context overrides or process environment.

---

set_env

inline

inline void set_env(std::string_view key, std::string_view value)

Defined in src/lib/sbio/core/context.hh:288

Provide a specific override for an environment variable that only the Context uses.

Note

Overrides will be searched first when the Context is queried for env vars, before then searching the actual process environment.

Note

There is no synchronization with overrides - should be set before moving Contexts between threads, for example.

Public Static Methods

Return	Name	Description
constexpr bool	supports static inline constexpr	Check if a particular parallelization method is supported (threads, MPI, etc.)
bool	validate_policy static inline	Check an EPolicy can be used with config, and IOPolicy, in the current env.

---

supports

static inline constexpr

constexpr static inline constexpr bool supports(ParallelizationMethods method)

Defined in src/lib/sbio/core/context.hh:169

Check if a particular parallelization method is supported (threads, MPI, etc.)

Returns

true if supported else false

Parameters

Parameter	Type	Description
method	ParallelizationMethods	The parallelization method

---

validate_policy

static inline

static inline bool validate_policy(const EPolicyConfig & config, std::string & error)

Defined in src/lib/sbio/core/context.hh:201

Check an EPolicy can be used with config, and IOPolicy, in the current env.

Returns

true if the policy can be configured else false.

Parameters

Parameter	Type	Description
config	const EPolicyConfig &	The EPolicy configuration parameters
error	std::string &	A description of the problem if not a usable compostion.

Public Types

Name	Description
IOPolicy
ExecutionPolicy
EPolicyConfig

---

IOPolicy

using IOPolicy = IO

Defined in src/lib/sbio/core/context.hh:94

---

ExecutionPolicy

using ExecutionPolicy = EPolicy

Defined in src/lib/sbio/core/context.hh:95

---

EPolicyConfig

using EPolicyConfig = typename EPolicy::Config

Defined in src/lib/sbio/core/context.hh:96

Private Attributes

Return	Name	Description
bool	m_ok
bool	m_registered
bool	m_io_environment	Whether this Context holds the IO environment.
std::string	m_error
std::map< std::string, std::string >	m_env

---

m_ok

bool m_ok { false }

Defined in src/lib/sbio/core/context.hh:304

---

m_registered

bool m_registered { false }

Defined in src/lib/sbio/core/context.hh:305

---

m_io_environment

bool m_io_environment { false }

Defined in src/lib/sbio/core/context.hh:306

Whether this Context holds the IO environment.

---

m_error

std::string m_error {}

Defined in src/lib/sbio/core/context.hh:307

---

m_env

std::map< std::string, std::string > m_env {}

Defined in src/lib/sbio/core/context.hh:308

Private Static Methods

Return	Name	Description
constexpr const char *	method_name static inline constexpr

---

method_name

static inline constexpr

constexpr static inline constexpr const char * method_name(ParallelizationMethods method)

Defined in src/lib/sbio/core/context.hh:293