4.6 Dynamic Compilation

Before executing SCIRun, be aware of the Dynamic Compilation feature.

Dynamic compilation is a technique used by SCIRun to discover and generate code for data types and algorithms used by modules in networks. This is done at runtime and once for each new data type and algorithm encountered. This technique provides a number of benefits not discussed here (see the publication Dynamic Compilation of C++ Template Code for details).

By default, code generated by dynamic compilation is stored in directory on-the-fly-libs in the user's home directory. The location of dynamically generated code can be changed by setting the value of the environment variable SCIRUN_ON_THE_FLY_LIBS_DIR to the desired directory.

For example:

for Bourne-like shells (sh, ksh, bash, etc,)

SCIRUN_ON_THE_FLY_LIBS_DIR=~/SCIRun/on-the-fly-libs
export SCIRUN_ON_THE_FLY_LIBS_DIR

for csh-like shells

setenv SCIRUN_ON_THE_FLY_LIBS_DIR ~/SCIRun/on-the-fly-libs

SCIRUN_ON_THE_FLY_LIBS_DIR can be set in the user's .scirunrc file.

SCIRUN_ON_THE_FLY_LIBS_DIR=/home/me/on-the-fly-libs

Setting a unique value of SCIRUN_ON_THE_FLY_LIBS_DIR for each SCIRun user has the following benefits:

• Allows multiple users to run the same instance of SCIRun without dynamic compilation conflicts. For example, by specifying an on-the-fly-libs directory in their home directory, a user can run SCIRun installed in /usr/local that another user is already running.

• Allows a /usr/local installation of SCIRun to be secure because it does not require /usr/local/.../on-the-fly-libs to be writable by all (a potential security risk).

• Allows greater debugging and multiple build support by allowing the user to change dynamically compiled code locations between instances of SCIRun.

Dynamic compilation causes a delay the first time a module is executed. The module changes color while it is being compiled.