# CA_HW3

## Building the environment

### install the verilator and install srv32

We install the verilator to compile Verilog code into C++, We install it by this following step:

`https://verilator.org/guide/latest/install.html`

Next, We build the RISC-V toolchains by x-pack

install lcov

sudo apt-get install lcov

install NVM

curl -sL https://deb.nodesource.com/setup_14.x | sudo -E bash -

sudo apt-get install gcc g++ make

sudo apt-get update && sudo apt-get install yarn

sudo apt install nodejs

sudo apt install build-essential

relative pack

sudo apt install build-essential ccache

export CROSS_COMPILE=riscv-none-embed-

sudo npm install --global xpm@latest

xpm --version

xpm init # Only at first use.

xpm install @xpack-dev-tools/riscv-none-embed-gcc@latest

ls -l xpacks/.bin

result：

cd xpacks/xpack-dev-tools-riscv-none-embed-gcc/.content/bin

pwd
/home/eecheng/Desktop/srv32/xpacks/xpack-dev-tools-riscv-none-embed-gcc/.content/bin

export PATH=$PATH:/home/eecheng/Desktop/srv32/xpacks/xpack-dev-tools-riscv-none-embed-gcc/.content/bin


Here, we can start to simulation with srv32

## simulation result of srv32

form gtkwave:

## optimization

We change `int` into `volatile int`

#include <stdio.h>
#include <limits.h>

int maxProfit(int* prices, int pricesSize){
    
    volatile int min_price=INT_MAX;
    volatile int p_gap=0;
    
    for (int i=0;i<pricesSize;i++){
          if(prices[i]<=min_price)
              min_price=prices[i]; //update min_price value
              
          if(prices[i]-min_price>=p_gap)
              p_gap=prices[i]-min_price; //update the newest price gap
    }
    
    return p_gap;
}

int main(){
  int prices[] = {7,1,5,3,6,4};
  printf("%d\n", maxProfit(prices,6));
  return 0;
}

here is the result:

0

Excuting 232 instructions, 420 cycles, 2.92 CPI
Program terminate
- ../rtl/../tb/tb.v:418: Verilog $finish

### Simulation statistics

Simulation time : 0.009 s
Simulation cycles: 528
Simulation speed : 0.07636 MHz

## reference

https://hackmd.io/@eecheng/B1fEgnQwF