EECS 281 Lecture 1

Proffice OH: 2632 BBB, check Google Calendar to make sure

T Th in Chrysler?

Required Texts:

• Intro to Algorithms
• C++ STL

Office Hours: http://eecs.help

Labs - Pre-lab work before lab section, worksheet at start of lab

Late submission/Midterm Regrades: [email protected]

• Midterm Regrades: write and compile/run code, send it to email

Projects - 21 days

C++14 Standard

CAEN Linux g++ (GCC) 5.1.0, might not compile here even if XCode compiles

Exams - MC and Code

Printing lectures before each class

• Before lecture - make questions
• After lecture - check over concepts for clarity, and check for added material

Project 1 specs are out - autograder will be up on weekend

GCC 5.1.0 is the not the default version on CAEN, check Project 0 Makefile to find how to gain access

Xcode, CAEN, emacs will be useful

Version control - Git (gitlab.eecs.umich.edu)

Plotting Tools - plot algorithm statistics

• Gnuplot, Excel, Matlab

READ the CLRS text to learn algorithms

Xcode debug, GDB debug - one line at a time

Valgrind debug - memory leaks

Profilers debug - what code the program is spending the most time in

//REQUIRES: in and out are arrays with size elements 
//MODIFIES: out
//EFFECTS: out[i] = in[0] *...* in[i-1] *

// * in[i+1] *...* in[size-1]

// REALLY BAD
void f(int *out, const int *in, int size) {
// for loop to multiply a certain value of out 
    for (i = 0; i < size; ++i) {
        out[i] = 1; // initialization
        for (j = 0; j < size; ++j) {
            if (i != j) {
                out[i] = out[i]*in[j]
            }
        }
    }
}

// MORE EFFICIENT
void f(int *out, const int *in, int size) {
// take total product once, then divide by value for each i in out
    int product = 1;
    for (int i = 0; i < size; ++i) {
        product *= in[i];
    }
    for (int i = 0; i < size; ++i) {
        if (in[i] != 0) {  // maybe will fix divide by 0? double CHECK 
            out[i] = product / in[i];
        }
    }
}

Office Hours - attend early for conceptual questions (bring beforehand), after attend for code questions

Post-Lecture Reimplementation on XCode

// Lecture 1 Algorithm Exercise
void f(int *out, const int *in, int size) {
    // take total product once, then divide by value for each i in out
    int product = 1;
    int zero_count = 0;
    for (int i = 0; i < size; ++i) {
        if (in[i] == 0) ++zero_count;
        else product *= in[i];
    }
    for (int i = 0; i < size; ++i) {
        if (zero_count == 0) out[i] = product / in[i];
        else if (zero_count == size) out[i] = 0;
        else if (in[i] == 0) {
            out[i] = product;
        }
        else out[i] = 0;
        cout << i << ": " << out[i] << endl; // test
    }
}

int main() {
    int size = 3;
    int in[3] = {3,2,0};
    int out[3];
    f(out, in, size);
    return 0;
}