Scilab is a mathematical computing program similar to MATLAB. It includes a graphical circuit designer and simulation tool called Xcos - this is similar to Simulink in MATLAB, but with less features. Scilab is an excellent tool for anyone to solve optimization problems. You can download additional toolboxes from the developer site.
v5.5 [Apr 17, 2014]
Highlights of Scilab 5.5.0:
New extended functionalities for GUI creations and best rendering of user interfaces
New uicontrols to create tabs, advanced and fully customizable graphical interfaces (adding icons, creating borders, etc.), new objects positioning and resizing capabilities.
New graphics capabilities providing users with an optimized interaction
Display of images in true colors, management of lighting on 3-D graphics, new interactions on graphics enabling to edit graphics handles directly on figures using the mouse.
MPI capabilities
Disabled by default, to leave the user the ability to adapt Scilab to its environment, MPI (The Message Passing Interface) capabilities are available in Scilab source tree for High Performance Computation users.
And also
An interface to directly interact with Java external objects from Scilab, a dedicated module to read/write HDF5 files and datasets, and the ability to easily localize Scilab external modules.
Mall Creeps
