OutlineMATLABPowerPoint PresentationMATLAB basicsMATLAB variablesMATLAB arraysMATLAB operationsSlide 8MATLAB functionsMATLAB programmingMATLAB ProgrammingCalling MATLABSlide 13Using MATLAB C LibrarySlide 15Slide 16Slide 17Slide 18Mixing Simple C and MATLAB CMultidimensional ArraysSlide 21Mixing Simple C and MATLABWorking with .mat filesOutlineOutline•Announcements–HWI due today, 5PM–HWII available later today–Sign-up for CTC account•MATLAB•Bringing MATLAB into CMATLABMATLAB•“MATrix LABoratory”•Started out as a front end for LINPACK, a linear algebra library that was the antecedent of LAPACK•MATLAB is an interactive system for scientific computing–lots of built-in functions–programmable–excellent graphics•But what is MATLAB?This is…This is…MATLAB basicsMATLAB basics•Interact with MATLAB through a command line•Commands are evaluated one-by-one•MATLAB stores variables in the “workspace”–Can get info on variables by typing “whos”MATLAB variablesMATLAB variables•MATLAB variables are 2D arrays of doubles (e.g. matrices)–Through V4, this was strictly true–V5 added ND-arrays, structs, and cell-arraysMATLAB arraysMATLAB arrays•Can create arrays with–brackets•A=[1 3 5;2 4 6];–commands like zeros, ones, rand•A=zeros(2,3);–colon operator•A=[1:2:5; 2:2:6];–or by loading a file•A=load(‘Cfinal.txt’);MATLAB operationsMATLAB operations•Arithmetic and logical operations in MATLAB are vectorized:–A=B+C is equivalent to for(j=0;j<nrows;j++){for(k=0;k<ncols;k++){A(j,k)=B(j,k)+C(j,k);}}•B and C must be same size or scalar–A=B*C is matrix multiplication•B: m-by-p, C: p-by-n, then A: m-by-nMATLAB operationsMATLAB operations•MATLAB’s “\” solves linear systems–x=A\b; %solves Ax=b–“\” is very smartMATLAB functionsMATLAB functions•MATLAB provides lots of built-in functions–Math: sin, cos, sqrt–Lin. Alg: eigs, svd, lu–Solve ODE’s–These are all vectorized•There are many toolboxes which contain additional functionsMATLAB programmingMATLAB programming•Can create new functions (m-files)–text files ending with .m & containing MATLAB commands –first line of file has form:•function [o1, o2,… oM]=name(i1,i2,… iN)Inputs -call-by-valueOutputs -value of o1, o2,etc at end will be returnedMATLAB ProgrammingMATLAB Programmingfunction [C]=SolveA(A,RHS);[m,n]=size(A);[p,q]=size(RHS);if(p!=m)error(‘RHS &A must have same number of rows’);endC=A\RHS;•MATLAB programs are simple and compact•Excellent language for prototypingCalling MATLABCalling MATLAB•C/C++ programs can make use of many of MATLAB’s nice features:–vectorized operations–complex types–linear algebra and math functionsCalling MATLABCalling MATLAB•Bring these capabilities to C was not easy–need to manage memory in a MATLAB-like way–need to call functions in a MATLAB-like wayUsing MATLAB C LibraryUsing MATLAB C Library•#include “matlab.h”--Matlab C-functions and types•Declare variables used with MATLAB functions to be –mxArray *volatile name=NULL;•Start MATLAB memory management–mlfEnterNewContext(nout,nin,outvars,invars);•nout,nin--number of MATLAB output/input variables•outvars--list of output variables•invars--list of input variables•for main, this is just (0,0)•Write your code•Destroy mxArray variables:–mlfDestroyArray(name);•Stop MATLAB memory management–mlfRestorePreviousContext(nout,nin,outvars,invars)Using MATLAB C LibraryUsing MATLAB C LibraryUsing MATLAB C LibraryUsing MATLAB C Library•Create with mbuild:–mbuild matccode.c–Passes matccode.c to C-compiler, and links to appropriate libraries•MATLAB Libraries–MATLAB C functions are included in several “Shared-Object” (.so) libraries–Will talk more about them on Wed.–Must add <matlab>/extern/lib/<arch> to LD_LIBRARY_PATH•setenv LD_LIBRARY_PATH /usr/local/matlab/extern/lib/sgi:/usr/local/matlab/extern/lib/sgi/bin/sgi:$LD_LIBRARY_PATHUsing MATLAB C LibraryUsing MATLAB C Library•A=<Matlab expression>–mlfAssign(&A,mlf expression)–Ex: A=B*C;•mlfAssign(&A,mlfMtimes(B,C))•Ex: [L,U]=lu(A);•Matlab function can take 1-2 inputs and produce up to 3 outputs•C-version provides this too–mlfAssign(&L,mlfLu(&U,NULL,A,NULL));Using MATLAB C LibraryUsing MATLAB C LibraryMixing Simple C and Mixing Simple C and MATLAB CMATLAB C•Converting C-arrays to mxArrays:–mlfAssign(&MXarray, mlfDoubleMatrix(m,n,Carray,NULL))–Copies contents of Carray (or first m*n elements) into Mxarray–For 1D arrays, this is straight-forward, but:Multidimensional ArraysMultidimensional Arrays1 2 34 5 6123456142536A=C: Row-majorMATLAB: Column-majorMultidimensional ArraysMultidimensional Arrays123456mlfAssign(&Marray, mlfDoubleMatrix(2,3,Carray,NULL))CarrayMarray1 3 52 4 61 2 34 5 6NOT:Mixing Simple C and Mixing Simple C and MATLABMATLAB•Converting from mxArrays to C–Get pointer to data in mxArray•double ptr;•ptr=mlfGetPt(A);–Use C function “memcpy”•memcpy(C,ptr,m*sizeof(double));–m is the amount of data in A to copy–m=prod(size(A));•MATLAB archives data in an efficient file type called .mat•We can read and write to .mat files from C–mlfSave(mxCreateString(”name.mat"),"w",•”o1",o1,”o2",o2,…,NULL);–mlfLoad(mxCreateString(“name.mat”),•“i1”,i1,”i2”,i2,…,NULL);Working with .mat filesWorking with .mat