REW - Revision history

Wbuytaert at 20:38, 10 April 2009

2009-04-10T20:38:32Z

Wbuytaert at 20:27, 10 April 2009

2009-04-10T20:27:27Z

Wbuytaert at 23:00, 27 February 2009

2009-02-27T23:00:30Z

Wbuytaert at 22:51, 27 February 2009

2009-02-27T22:51:48Z

Wbuytaert at 10:41, 11 February 2009

2009-02-11T10:41:00Z

Wbuytaert at 19:48, 2 February 2009

2009-02-02T19:48:16Z

Wbuytaert at 17:15, 2 February 2009

2009-02-02T17:15:37Z

New page

[[Category:Projects]]
[[Category:Hydrology in R]]

== Introduction ==

This page collects information about the application of the Representative Elementary Watershed model.

== Versions ==

=== THREW ===

C version maintained by Fuqiang Tian (University of Illinois)

=== CREW ===

FORTRAN version maintained by Haksu Lee

== Installation ==

=== THREW ===

==== Macintosh / linux ====

An easy way to install on mac and linux is by creating first static libraries for the solver and then linking those in the application. The advantage of this is that you don't need to recompile the solver each time you make changes to the model, which is quicker. Compiling it this way involves the following steps:

* download the cvode solver from the [https://computation.llnl.gov/casc/sundials/download/download.html cvode/sundials website] At the time of writing that is cvode-2.5.0.tar.gz

* decompress cvode-2.5.0.tar.gz, and add the directory /include/threw/ from the threw model to ''cvode-2.5.0/include''. Replace the file ''cvode-2.5.0/src/cvode/cvode.c'' with the one included in the THREW model.

* Compile the solver with the changes we just made. This can be done with the following commands from within the cvode-2.5.0 directory:

./configure
./make

* copy the static libraries, which reside in a hidden directory

cp src/cvode/.libs/libsundials_cvode.a ./
cp src/nvec_ser/.libs/libsundials_nvecserial.a ./

* then copy both files (libsundials_cvode.a and libsundials_nvecserial.a) into the ''src'' directory of the THREW model.

* now you should be able to compile the threw model with the following command:

gcc -pipe threw_closure.c threw_error.c threw_f.c threw_init.c threw_io.c threw_utility.c threw2.c -o threw2 \
-L. -lsundials_cvode -lsundials_nvecserial -I../include

== Developers and applications ==

afaik, the following institutes / persons use a version of the REW model

* University of Illinois at Urbana Champaign
* University of Bristol (Wouter Buytaert)
* T U Munchen

@@ Line 75: / Line 75: @@
 and then initialised with:
       CVodeMalloc(cvode_mem, f, CData.T0, w, CV_SS, CData.RTOL, &CData.ATOL)
 where:
 * cvode_mem is the structure to be initialised
 * f is the right hand side function

@@ Line 55: / Line 55: @@
       CVode(cvode_mem, tout, w, &t, CV_NORMAL)
-This function solves the differential equations up to time ''tout''. ''tout'' is the time at which output is shown on the screen while the model is running, and may cover many hydrological time steps. ''w'' is a vector of results at this timestep.
+This function solves the differential equations up to time ''tout''. ''tout'' is the current time in seconds. ''w'' is a vector of results at each timestep.
-TODO: where is ''tout'' defined, and we may want to check the above is correct by altering ''tout''. This should only have an impact on what is shown on the screen, but not on the final model results
+QUESTION: Does the fact that ''tout'' is defined in seconds mean that the internal time step of the solver is seconds? Any way of making this more flexible?
 All the data for running the model are stored in the structure ''cvode_mem''. This is a very complex structure that is understood by the solver. It contains everything from model state variables, parameters, as well as the 'right hand side function'. It is this function that is solved by the solver. It is basically the entire hydrological model, represented as a set of differential equations. In the threw code, the function is constructed in threw_f.c. It ''contains'' all the closure relations, which, individually, are defined in threw_closure.c.
@@ Line 67: / Line 69: @@
 === Structure of cvode_mem ===
-todo
+The structure of cvode_mem is internal to the solver and we do not really need to know this. cvode_mem is created with:
 == Developers and applications ==

@@ Line 43: / Line 43: @@
       gcc -pipe threw_closure.c threw_error.c threw_f.c threw_init.c threw_io.c threw_utility.c threw2.c -o threw2 \
-      -L. -lsundials_cvode -lsundials_nvecserial -I../include
+      -L. -lsundials_cvode -lsundials_nvecserial -I../include -lm
 Why do we need to patch the solver? Only one thing changes: after each hydrological time step the function ''W2Flux()'' is executed. This is necessary to add external fluxes, such as rain. In its original form, the solver solves a differential equation from a certain initial state without further external intervention. In a hydrological model however, we may need to update the internal states after each timestep, for instance by adding rain, or taking away evapotranspiration. This is what ''W2Flux()'' does.

@@ Line 32: / Line 32: @@
       ./configure
       make
 * copy the static libraries, which reside in a hidden directory

@@ Line 28: / Line 28: @@
 * decompress cvode-2.5.0.tar.gz, and add the directory /include/threw/ from the threw model to ''cvode-2.5.0/include''. Replace the file ''cvode-2.5.0/src/cvode/cvode.c'' with the one included in the THREW model.
-* Compile the solver with the changes we just made. This can be done with the following commands from within the cvode-2.5.0 directory:
+* Compile the solver with the changes we just made. This can be done with the following commands from within the cvode-2.5.0 directory. Note: we do not need to install the library (''make install'') since we will just copy the static libraries for use in threw.
       ./configure
@@ Line 38: / Line 38: @@
       cp src/nvec_ser/.libs/libsundials_nvecserial.a ./
-* then copy both files (libsundials_cvode.a and libsundials_nvecserial.a) into the ''src'' directory of the THREW model.
+* then copy both files (''libsundials_cvode.a'' and ''libsundials_nvecserial.a'') into the ''src'' directory of the THREW model. You may now throw away the cvode-2.5.0/ folder since both files (which are static libraries) contain all the functionality we need.
-* now you should be able to compile the threw model with the following command:
+* Now you should be able to compile the threw model with the following command:
       gcc -pipe threw_closure.c threw_error.c threw_f.c threw_init.c threw_io.c threw_utility.c threw2.c -o threw2 \
       -L. -lsundials_cvode -lsundials_nvecserial -I../include
 == Developers and applications ==