PaVM

Hello there!

This repo is created for publishing the source code of PaVM, a smart contract virtual machine that supports inter- and inner-contract parallel execution.

Get started

# enable compile.sh executable
chmod +x compile.sh

# compile PaVM
./compile.sh

Introduction

Key instructions

The newly added instructions in PaVM is listed as follows:

Type	Mnemonic	Opcode	Context
Thread	control	SUBSOL	0xA1
Thread	control	SLEEP	0xA2
Thread	control	REVERTT	0xA3
Data	control	AFTERW	0xA4
Data	control	AFTERR	0xA5
Data	control	AFTERA	0xA6
Runtime	record	RR	0xA7
Runtime	record	RPHASH	0xA8
Runtime	record	RDR	0xA9
Runtime	record	WTR	0xAA

The implementation of each instruction obeies the following code:

func op[insturction_name] (ret) {stack..}{
  // get the args from VM Stack
  // instruction specific logic
  // return value
}

New data area

PaVM provides several data areas to store the multithread-related data as follows:

• Thread Data
• Record Data
• Thread State Table

The implementation of the above areas can be found in /core/vm/ folder.

Besides, PaVM also supports typical areas such as:

• Stack
• Persistent Storage

Enable parallel!

Key interfaces for developer

The features such as multithreading can be enabled by interfaces/keywords provided by PaVM:

Have a try with this demo contract:

contract WordCount {
  function count(string textSegment) {
    mapping string[int] ret;
    for(int i = 0; i < len(textSegment); i++) {
      string word = textSegment[i];
      ret[word] == NULL ? ret[word] = 0 : ret[word]++;
    }
    return ret;
}
11
12 /* Enable runtime record and hash computing in main function */
13 function rr rphash main(string text) {
14 int length = len(text);
15
16 mapping tempRet1 = subsol [1] count(text[0 : length/2]);
17 mapping tempRet2 = subsol [2] count(text[length/2 : length]);
18 sleep [1] 1000; // No.1 thread sleeps for 1000ms
19 revertt [2]; // Revert the operations made by No.2 thread
20
21 /* Join the two temporary values by embedded function */
22 return join(tempRet1, tempRet2);
23 }
24 }