616
V. Skorych et al.
library was utilized as the lower layer of the data processing subsystem, where it
is responsible for all direct work with the computer file system. The conversion
between the Dyssol data format and the HDF5 data format is performed only during
data serialization and deserialization, so the modelling system can use suitable and
optimized data structures during its operation.
6.2 Dynamic Data Caching
One of the difficulties that arise when applying distributed parameters in dynamic
simulations is the continuous generation of significant amounts of data. If the set of
distributed parameters and the number of discretization classes for each dimension
are not limited, the complexity of the flowsheets under study can be restricted by the
free RAM of the computer.
To solve this problem, a subsystem for dynamic data caching was developed and
implemented in Dyssol. Its work is based on the fact that at each moment the simulation framework works only with certain groups of units (partitions) in a certain time
interval. The rest of the information is not used, so it can be temporarily unloaded
from RAM. Therefore, at each moment of operation, the system stores only information about several time points from those material streams that are currently being
involved in the calculations. For greater flexibility, the caching algorithm is applied
for each material stream independently.
To minimize the impact of slow data backup and recovery, one must correctly
select the time interval that will be available from the working memory. Since the
Dyssol simulation system uses the waveform relaxation method, this interval should
take into account the current size of the time window. On the one hand, if the boundary
of the cached interval is inside the current time window, data backup and recovery
will be performed at each iteration of the WRM, on the other hand, too large cache
windows will increase the amount of unused information stored in RAM. Since for
the correct operation of the waveform relaxation method, it is necessary to interpolate
data from the previous time window, the minimum size of the uncached interval is
2 · t W INDOW (current and previous window) for each material stream in the partition.
7 Materials Database
The implemented materials database gives the option to choose from a set of predefined materials or to define new compounds. In addition to existing material properties, the user can define his own set. All of them are divided into constant properties
and properties depending on temperature and/or pressure. While constant parameters, like molar mass, critical temperature and standard formation enthalpy, cannot
change their value during the simulations, temperature or pressure (TP) depended
parameters, like enthalpy or vapour pressure, have to be evaluated at runtime. The TP
V. Skorych et al.
library was utilized as the lower layer of the data processing subsystem, where it
is responsible for all direct work with the computer file system. The conversion
between the Dyssol data format and the HDF5 data format is performed only during
data serialization and deserialization, so the modelling system can use suitable and
optimized data structures during its operation.
6.2 Dynamic Data Caching
One of the difficulties that arise when applying distributed parameters in dynamic
simulations is the continuous generation of significant amounts of data. If the set of
distributed parameters and the number of discretization classes for each dimension
are not limited, the complexity of the flowsheets under study can be restricted by the
free RAM of the computer.
To solve this problem, a subsystem for dynamic data caching was developed and
implemented in Dyssol. Its work is based on the fact that at each moment the simulation framework works only with certain groups of units (partitions) in a certain time
interval. The rest of the information is not used, so it can be temporarily unloaded
from RAM. Therefore, at each moment of operation, the system stores only information about several time points from those material streams that are currently being
involved in the calculations. For greater flexibility, the caching algorithm is applied
for each material stream independently.
To minimize the impact of slow data backup and recovery, one must correctly
select the time interval that will be available from the working memory. Since the
Dyssol simulation system uses the waveform relaxation method, this interval should
take into account the current size of the time window. On the one hand, if the boundary
of the cached interval is inside the current time window, data backup and recovery
will be performed at each iteration of the WRM, on the other hand, too large cache
windows will increase the amount of unused information stored in RAM. Since for
the correct operation of the waveform relaxation method, it is necessary to interpolate
data from the previous time window, the minimum size of the uncached interval is
2 · t W INDOW (current and previous window) for each material stream in the partition.
7 Materials Database
The implemented materials database gives the option to choose from a set of predefined materials or to define new compounds. In addition to existing material properties, the user can define his own set. All of them are divided into constant properties
and properties depending on temperature and/or pressure. While constant parameters, like molar mass, critical temperature and standard formation enthalpy, cannot
change their value during the simulations, temperature or pressure (TP) depended
parameters, like enthalpy or vapour pressure, have to be evaluated at runtime. The TP