pidiver.go

package pidiver

import (
	//	"fmt"
	"encoding/binary"
	"errors"
	"github.com/iotaledger/iota.go/trinary"
	"github.com/shufps/bcm2835"
	"log"
	//"math/rand"
	"time"
	"unsafe"
)

const (
	SPI_CS                    = 5
	FLAG_RUNNING       uint32 = (1 << 0)
	FLAG_FOUND         uint32 = (1 << 1)
	FLAG_OVERFLOW      uint32 = (1 << 2)
	FLAG_CURL_FINISHED uint32 = (1 << 3)

	FLAG_START        uint32 = (1 << 0)
	FLAG_CURL_RESET   uint32 = (1 << 1)
	FLAG_CURL_WRITE   uint32 = (1 << 2)
	FLAG_CURL_DO_CURL uint32 = (1 << 3)

	CMD_NOP                        uint32 = 0x00000000
	CMD_WRITE_FLAGS                uint32 = 0x04000000
	CMD_RESET_WRPTR                uint32 = 0x08000000
	CMD_WRITE_DATA                 uint32 = 0x10000000
	CMD_WRITE_MIN_WEIGHT_MAGNITUDE uint32 = 0x20000000
	CMD_READ_FLAGS                 uint32 = 0x84000000
	CMD_READ_NONCE                 uint32 = 0x88000000
	CMD_READ_CRC32                 uint32 = 0x90000000

	NONCE_TRINARY_SIZE = 81
	STATE_LENGTH       = 729
	HASH_LENGTH        = 243
	TRYTE_CHARS        = "9ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	DATA_WIDTH         = 9

	BCM2835_SPI_BIT_ORDER_LSBFIRST = 0 ///< LSB First
	BCM2835_SPI_BIT_ORDER_MSBFIRST = 1 ///< MSB First

	BCM2835_SPI_MODE0 = 0 ///< CPOL = 0, CPHA = 0
	BCM2835_SPI_MODE1 = 1 ///< CPOL = 0, CPHA = 1
	BCM2835_SPI_MODE2 = 2 ///< CPOL = 1, CPHA = 0
	BCM2835_SPI_MODE3 = 3 ///< CPOL = 1, CPHA = 1

	BCM2835_SPI_CS0     = 0 ///< Chip Select 0
	BCM2835_SPI_CS1     = 1 ///< Chip Select 1
	BCM2835_SPI_CS2     = 2 ///< Chip Select 2 (ie pins CS1 and CS2 are asserted)
	BCM2835_SPI_CS_NONE = 3 ///< No CS, control it yourself

	BCM2835_SPI_CLOCK_DIVIDER_65536 uint16 = 0     ///< 65536 = 262.144us = 3.814697260kHz
	BCM2835_SPI_CLOCK_DIVIDER_32768 uint16 = 32768 ///< 32768 = 131.072us = 7.629394531kHz
	BCM2835_SPI_CLOCK_DIVIDER_16384 uint16 = 16384 ///< 16384 = 65.536us = 15.25878906kHz
	BCM2835_SPI_CLOCK_DIVIDER_8192  uint16 = 8192  ///< 8192 = 32.768us = 30/51757813kHz
	BCM2835_SPI_CLOCK_DIVIDER_4096  uint16 = 4096  ///< 4096 = 16.384us = 61.03515625kHz
	BCM2835_SPI_CLOCK_DIVIDER_2048  uint16 = 2048  ///< 2048 = 8.192us = 122.0703125kHz
	BCM2835_SPI_CLOCK_DIVIDER_1024  uint16 = 1024  ///< 1024 = 4.096us = 244.140625kHz
	BCM2835_SPI_CLOCK_DIVIDER_512   uint16 = 512   ///< 512 = 2.048us = 488.28125kHz
	BCM2835_SPI_CLOCK_DIVIDER_256   uint16 = 256   ///< 256 = 1.024us = 976.5625MHz
	BCM2835_SPI_CLOCK_DIVIDER_128   uint16 = 128   ///< 128 = 512ns = = 1.953125MHz
	BCM2835_SPI_CLOCK_DIVIDER_64    uint16 = 64    ///< 64 = 256ns = 3.90625MHz
	BCM2835_SPI_CLOCK_DIVIDER_32    uint16 = 32    ///< 32 = 128ns = 7.8125MHz
	BCM2835_SPI_CLOCK_DIVIDER_16    uint16 = 16    ///< 16 = 64ns = 15.625MHz
	BCM2835_SPI_CLOCK_DIVIDER_8     uint16 = 8     ///< 8 = 32ns = 31.25MHz
	BCM2835_SPI_CLOCK_DIVIDER_4     uint16 = 4     ///< 4 = 16ns = 62.5MHz
	BCM2835_SPI_CLOCK_DIVIDER_2     uint16 = 2     ///< 2 = 8ns = 125MHz, fastest you can get
	BCM2835_SPI_CLOCK_DIVIDER_1     uint16 = 1     ///< 0 = 262.144us = 3.814697260kHz, same as 0/65536

)

var crctab = []uint32{
	0x00000000,
	0x04C11DB7, 0x09823B6E, 0x0D4326D9, 0x130476DC, 0x17C56B6B,
	0x1A864DB2, 0x1E475005, 0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6,
	0x2B4BCB61, 0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD,
	0x4C11DB70, 0x48D0C6C7, 0x4593E01E, 0x4152FDA9, 0x5F15ADAC,
	0x5BD4B01B, 0x569796C2, 0x52568B75, 0x6A1936C8, 0x6ED82B7F,
	0x639B0DA6, 0x675A1011, 0x791D4014, 0x7DDC5DA3, 0x709F7B7A,
	0x745E66CD, 0x9823B6E0, 0x9CE2AB57, 0x91A18D8E, 0x95609039,
	0x8B27C03C, 0x8FE6DD8B, 0x82A5FB52, 0x8664E6E5, 0xBE2B5B58,
	0xBAEA46EF, 0xB7A96036, 0xB3687D81, 0xAD2F2D84, 0xA9EE3033,
	0xA4AD16EA, 0xA06C0B5D, 0xD4326D90, 0xD0F37027, 0xDDB056FE,
	0xD9714B49, 0xC7361B4C, 0xC3F706FB, 0xCEB42022, 0xCA753D95,
	0xF23A8028, 0xF6FB9D9F, 0xFBB8BB46, 0xFF79A6F1, 0xE13EF6F4,
	0xE5FFEB43, 0xE8BCCD9A, 0xEC7DD02D, 0x34867077, 0x30476DC0,
	0x3D044B19, 0x39C556AE, 0x278206AB, 0x23431B1C, 0x2E003DC5,
	0x2AC12072, 0x128E9DCF, 0x164F8078, 0x1B0CA6A1, 0x1FCDBB16,
	0x018AEB13, 0x054BF6A4, 0x0808D07D, 0x0CC9CDCA, 0x7897AB07,
	0x7C56B6B0, 0x71159069, 0x75D48DDE, 0x6B93DDDB, 0x6F52C06C,
	0x6211E6B5, 0x66D0FB02, 0x5E9F46BF, 0x5A5E5B08, 0x571D7DD1,
	0x53DC6066, 0x4D9B3063, 0x495A2DD4, 0x44190B0D, 0x40D816BA,
	0xACA5C697, 0xA864DB20, 0xA527FDF9, 0xA1E6E04E, 0xBFA1B04B,
	0xBB60ADFC, 0xB6238B25, 0xB2E29692, 0x8AAD2B2F, 0x8E6C3698,
	0x832F1041, 0x87EE0DF6, 0x99A95DF3, 0x9D684044, 0x902B669D,
	0x94EA7B2A, 0xE0B41DE7, 0xE4750050, 0xE9362689, 0xEDF73B3E,
	0xF3B06B3B, 0xF771768C, 0xFA325055, 0xFEF34DE2, 0xC6BCF05F,
	0xC27DEDE8, 0xCF3ECB31, 0xCBFFD686, 0xD5B88683, 0xD1799B34,
	0xDC3ABDED, 0xD8FBA05A, 0x690CE0EE, 0x6DCDFD59, 0x608EDB80,
	0x644FC637, 0x7A089632, 0x7EC98B85, 0x738AAD5C, 0x774BB0EB,
	0x4F040D56, 0x4BC510E1, 0x46863638, 0x42472B8F, 0x5C007B8A,
	0x58C1663D, 0x558240E4, 0x51435D53, 0x251D3B9E, 0x21DC2629,
	0x2C9F00F0, 0x285E1D47, 0x36194D42, 0x32D850F5, 0x3F9B762C,
	0x3B5A6B9B, 0x0315D626, 0x07D4CB91, 0x0A97ED48, 0x0E56F0FF,
	0x1011A0FA, 0x14D0BD4D, 0x19939B94, 0x1D528623, 0xF12F560E,
	0xF5EE4BB9, 0xF8AD6D60, 0xFC6C70D7, 0xE22B20D2, 0xE6EA3D65,
	0xEBA91BBC, 0xEF68060B, 0xD727BBB6, 0xD3E6A601, 0xDEA580D8,
	0xDA649D6F, 0xC423CD6A, 0xC0E2D0DD, 0xCDA1F604, 0xC960EBB3,
	0xBD3E8D7E, 0xB9FF90C9, 0xB4BCB610, 0xB07DABA7, 0xAE3AFBA2,
	0xAAFBE615, 0xA7B8C0CC, 0xA379DD7B, 0x9B3660C6, 0x9FF77D71,
	0x92B45BA8, 0x9675461F, 0x8832161A, 0x8CF30BAD, 0x81B02D74,
	0x857130C3, 0x5D8A9099, 0x594B8D2E, 0x5408ABF7, 0x50C9B640,
	0x4E8EE645, 0x4A4FFBF2, 0x470CDD2B, 0x43CDC09C, 0x7B827D21,
	0x7F436096, 0x7200464F, 0x76C15BF8, 0x68860BFD, 0x6C47164A,
	0x61043093, 0x65C52D24, 0x119B4BE9, 0x155A565E, 0x18197087,
	0x1CD86D30, 0x029F3D35, 0x065E2082, 0x0B1D065B, 0x0FDC1BEC,
	0x3793A651, 0x3352BBE6, 0x3E119D3F, 0x3AD08088, 0x2497D08D,
	0x2056CD3A, 0x2D15EBE3, 0x29D4F654, 0xC5A92679, 0xC1683BCE,
	0xCC2B1D17, 0xC8EA00A0, 0xD6AD50A5, 0xD26C4D12, 0xDF2F6BCB,
	0xDBEE767C, 0xE3A1CBC1, 0xE760D676, 0xEA23F0AF, 0xEEE2ED18,
	0xF0A5BD1D, 0xF464A0AA, 0xF9278673, 0xFDE69BC4, 0x89B8FD09,
	0x8D79E0BE, 0x803AC667, 0x84FBDBD0, 0x9ABC8BD5, 0x9E7D9662,
	0x933EB0BB, 0x97FFAD0C, 0xAFB010B1, 0xAB710D06, 0xA6322BDF,
	0xA2F33668, 0xBCB4666D, 0xB8757BDA, 0xB5365D03, 0xB1F740B4}

var parallel uint32
var log2 int
var tryteMap map[string]uint32

func InitPiDiver() error {
	err := bcm2835.Init() // Initialize the library
  	if err != nil {
		return errors.New("Couldn't initialize BCM2835 Lib")
	}	
	
	/* init spi interface */
	bcm2835.SpiBegin()
	bcm2835.SpiSetBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST) /* default */
	bcm2835.SpiSetDataMode(BCM2835_SPI_MODE0)              /* default */
	bcm2835.SpiSetClockDivider(BCM2835_SPI_CLOCK_DIVIDER_32)
	bcm2835.SpiChipSelect(BCM2835_SPI_CS_NONE) /* default */

	bcm2835.GpioFsel(SPI_CS, bcm2835.Output)

	bcm2835.GpioSet(SPI_CS)
	time.Sleep(10 * time.Millisecond)
	bcm2835.GpioClr(SPI_CS)
	time.Sleep(10 * time.Millisecond)
	bcm2835.GpioSet(SPI_CS)
	time.Sleep(10 * time.Millisecond)

	parallel = readParallelLevel()
	log.Printf("Parallel Level Detected: %d\n", parallel)

	// log2(parallel)
	log2 = 0
	for i := 0; i < 32; i++ {
		if (parallel & (1 << uint32(i))) != 0 {
			log2 = i
		}
	}

	// table calculates all bits for AAA -> ZZZ including byte-swap
	tryteMap = make(map[string]uint32)
	for i := 0; i < 27; i++ {
		for j := 0; j < 27; j++ {
			for k := 0; k < 27; k++ {
				key := string(TRYTE_CHARS[i:i+1] + TRYTE_CHARS[j:j+1] + TRYTE_CHARS[k:k+1])
				xtrits, _ := trinary.TrytesToTrits(key)
				uint32Data := uint32(0)
				tritslo := uint32(0)
				tritshi := uint32(0)
				for j := 0; j < 9; j++ {
					tmpHi, tmpLo := tritToBits(xtrits[j])
					tritslo |= tmpLo << uint32(j)
					tritshi |= tmpHi << uint32(j)
				}
				uint32Data = swapBytes((tritslo & 0x000001ff) | ((tritshi & 0x000001ff) << 9) | CMD_WRITE_DATA)
				tryteMap[key] = uint32Data
			}
		}
	}
	log.Printf("Table calculated\n")
	return nil
}

// send command
func send(data uint32) {
	var bytedata []byte = make([]byte, 4)
	binary.BigEndian.PutUint32(bytedata, data)
	bcm2835.GpioClr(SPI_CS)
	bcm2835.SpiTransfern(bytedata)
	bcm2835.GpioSet(SPI_CS)
}

// send block of data for midstate
func sendBlock(data []uint32) {
	for i := 0; i < len(data); i++ {
		bytedata := *(*[4]byte)(unsafe.Pointer(&data[i]))
		bcm2835.GpioClr(SPI_CS)
		bcm2835.SpiTransfern(bytedata[:])
		bcm2835.GpioSet(SPI_CS)
	}
}

// send and receive
func sendReceive(cmd uint32) uint32 {
	bytedata := make([]byte, 4)
	bytedata_read := make([]byte, 4)
	binary.BigEndian.PutUint32(bytedata, cmd)

	bcm2835.GpioClr(SPI_CS)
	bcm2835.SpiTransfern(bytedata)
	bcm2835.GpioSet(SPI_CS)
	bcm2835.GpioClr(SPI_CS)
	bcm2835.SpiTransfernb(bytedata_read, bytedata_read)
	bcm2835.GpioSet(SPI_CS)
	return binary.BigEndian.Uint32(bytedata_read)
}

// start PoW
func startPow() {
	send(CMD_WRITE_FLAGS | FLAG_START)
}

// reset write pointer on FPGA
func resetWritePointer() {
	send(CMD_RESET_WRPTR)
}

// not used ... faster version with tables is used
func writeData(tritshi uint32, tritslo uint32) {
	cmd := CMD_WRITE_DATA

	cmd |= tritslo & 0x000001ff
	cmd |= (tritshi & 0x000001ff) << 9

	send(cmd)
}

// read parallel level of FPGA
func readParallelLevel() uint32 {
	return (sendReceive(CMD_READ_FLAGS) & 0x000000f0) >> 4
}

// read binary nonce
func readBinaryNonce() uint32 {
	return sendReceive(CMD_READ_NONCE)
}

// red CRC32
func readCRC32() uint32 {
	return sendReceive(CMD_READ_CRC32)
}

func writeMinWeightMagnitude(bits uint32) {
	if bits > 26 {
		bits = 26
	}
	send(CMD_WRITE_MIN_WEIGHT_MAGNITUDE | ((1 << bits) - 1))
}

// get Mask
func getMask() uint32 {
	return ((sendReceive(CMD_READ_FLAGS) >> 8) & ((1 << parallel) - 1))
}

// get Flags
func getFlags() uint32 {
	return sendReceive(CMD_READ_FLAGS) & 0x0000000f
}

// convert bits to trit
func bitsToTrits(h uint8, l uint8) int8 {
	if h != 0 && l != 0 {
		return 0
	}
	if h != 0 && l == 0 {
		return 1
	}
	if h == 0 && l != 0 {
		return -1
	}
	return -128
}

// convert trit to bits
func tritToBits(trit int8) (uint32, uint32) {
	switch trit {
	case 0:
		return 0x1, 0x1
	case -1:
		return 0x0, 0x1
	case 1:
		return 0x1, 0x0
	default:
		return 0x0, 0x0
	}
}

// calculate CRC32-MPEG
func crc(bytes []byte, l int) uint32 {
	value := uint32(0xffffffff)
	for i := 0; i < l; i++ {
		value = (value << 8) ^ crctab[((value>>24)^uint32(bytes[i]))&0xff]
	}
	return value
}

// swap bytes
func swapBytes(data uint32) uint32 {
	return ((data & 0xff000000) >> 24) |
		((data & 0x00ff0000) >> 8) |
		((data & 0x0000ff00) << 8) |
		((data & 0x000000ff) << 24)
}

// send trytes for midstate calculation and check for transmission errors
func sendTritData(trytes string) error {
	uint32Data := make([]uint32, HASH_LENGTH/DATA_WIDTH)
	verifyData := make([]uint32, HASH_LENGTH/DATA_WIDTH)
	for tries := 1; ; tries++ {
		for i := 0; i < HASH_LENGTH/DATA_WIDTH; i++ {
			key := trytes[i*3 : i*3+3]
			uint32Data[i] = tryteMap[key]
			verifyData[i] = (uint32Data[i] & 0xffff0300) | (uint32(i)&0x3f)<<10 | (uint32(i)&0xc0)>>6
		}
		resetWritePointer()
		sendBlock(uint32Data)
		verifyBytes := *(*[HASH_LENGTH / DATA_WIDTH * 4]byte)(unsafe.Pointer(&verifyData[0]))

		crc32Verify := crc(verifyBytes[:], len(verifyBytes))
		crc32 := readCRC32()
		//		log.Printf("CRC32: %08x\n", crc32)
		//		log.Printf("CRC32 Verify: %08x\n", crc32Verify)

		if crc32Verify != crc32 {
			log.Printf("Transfer Error (%d/10).\n", tries)
			tries++
			if tries == 11 {
				return errors.New("CRC32 error - giving up ...")
			}
			continue
		} else {
			break
		}
		break
	}
	return nil
}

// send block for midstate calculation
func curlSendBlock(trytes string, doCurl bool) error {
	if err := sendTritData(trytes); err != nil {
		return err
	}
	cmd := CMD_WRITE_FLAGS | FLAG_CURL_WRITE
	if doCurl {
		cmd |= FLAG_CURL_DO_CURL
	}
	send(cmd)
	
	// instantly read back ... curl needs <1µs on fpga and spi is slower
	if getFlags() & FLAG_CURL_FINISHED == 0 {
		return errors.New("Curl didn't finish")
	}
	return nil
}

// setup fpga for midstate calculation
func curlInitBlock() {
	send(CMD_WRITE_FLAGS | FLAG_CURL_RESET)
}

// do PoW
func PowPiDiver(trytes trinary.Trytes, minWeight int) (trinary.Trytes, error) {
	// do mid-state-calculation on FPGA
	start := time.Now()
	curlInitBlock()
	for blocknr := 0; blocknr < 33; blocknr++ {
		doCurl := true
		if blocknr == 32 {
			doCurl = false
		}
		if err := curlSendBlock(string(trytes)[blocknr*(HASH_LENGTH/3):(blocknr+1)*(HASH_LENGTH/3)], doCurl); err != nil {
			return "", err
		}
	}
	elapsed := time.Since(start)
	log.Printf("MidState: %s", elapsed)

	// write min weight magnitude
	writeMinWeightMagnitude(uint32(minWeight))

	// start PoW
	startPow()

	start = time.Now()
	for {
		flags := getFlags()

		if (flags&FLAG_RUNNING) == 0 && ((flags&FLAG_FOUND) != 0 || (flags&FLAG_OVERFLOW) != 0) {
			break
		}
		time.Sleep(1 * time.Millisecond)
	}
	elapsed = time.Since(start)
	log.Printf("Pow: %s", elapsed)

	binary_nonce := readBinaryNonce() - 2 // -2 because of pipelining for speed on FPGA
	mask := getMask()

	log.Printf("Found nonce: %08x (mask: %08x)\n", binary_nonce, mask)

	if mask == 0 {
		return "", errors.New("Returned Mask Zero")
	}

	// find set bit in mask
	found_bit := uint32(0)
	for i := uint32(0); i < parallel; i++ {
		if mask&(1<<i) != 0 {
			found_bit = i
			break
		}
	}

	// assemble nonce
	bitsLo := make([]uint8, NONCE_TRINARY_SIZE)
	bitsHi := make([]uint8, NONCE_TRINARY_SIZE)

	for i := 0; i < NONCE_TRINARY_SIZE; i++ {
		bitsLo[i] = 0x1
		bitsHi[i] = 0x1
	}

	// insert PIDIVER at beginning of nonce
	sigLo := []byte{0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1}
	sigHi := []byte{1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1}

	for i := 0; i < 24; i++ {
		bitsLo[i] = sigLo[i]
		bitsHi[i] = sigHi[i]
	}

	// insert initial nonce trits bit thingies
	for j := 0; j <= log2; j++ {
		bitsLo[j+24] = uint8((found_bit >> uint32(j)) & 0x1)
		bitsHi[j+24] = uint8((^(found_bit >> uint32(j))) & 0x1)
	}

	// insert nonce counter
	for i := 0; i < 32; i++ {
		bitsLo[NONCE_TRINARY_SIZE-32+i] = uint8((binary_nonce >> uint32(i)) & 0x1)
		bitsHi[NONCE_TRINARY_SIZE-32+i] = uint8(((^binary_nonce) >> uint32(i)) & 0x1)
	}

	// convert trits to trytes
	nonceTrits := make([]int8, NONCE_TRINARY_SIZE)
	for i := 0; i < NONCE_TRINARY_SIZE; i++ {
		nonceTrits[i] = bitsToTrits(bitsHi[i], bitsLo[i])
	}

	rettrytes, _ := trinary.TritsToTrytes(nonceTrits)
	return rettrytes, nil
}

/*
func main() {
	// test transaction data
	var transaction string = "999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999A9RGRKVGWMWMKOLVMDFWJUHNUNYWZTJADGGPZGXNLERLXYWJE9WQHWWBMCPZMVVMJUMWWBLZLNMLDCGDJ999999999999999999999999999999999999999999999999999999YGYQIVD99999999999999999999TXEFLKNPJRBYZPORHZU9CEMFIFVVQBUSTDGSJCZMBTZCDTTJVUFPTCCVHHORPMGCURKTH9VGJIXUQJVHK999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"

	var piDiver = PiDiver{}
	piDiver.init()

	mwm := 14
	randomTrytes := make([]rune, 256)

	for i := 0; i < 10000; i++ {
		for j := 0; j < 256; j++ {
			randomTrytes[j] = rune(TRYTE_CHARS[rand.Intn(len(TRYTE_CHARS))])
		}

		ret, err := piDiver.DoPoW(string(randomTrytes)+transaction[256:], mwm)

		if err != nil {
			log.Fatalf("Error: %g", err)
		}

		log.Printf("Nonce-Trytes: %s\n", ret)
		// verify result
		/*		trytes := giota.Trytes(string(randomTrytes) + transaction[256:len(transaction)-27] + ret[0:27])
				log.Printf("hash: %s\n\n", trytes.Hash())
				tritsHash := trytes.Hash().Trits()
				for i:=0;i<mwm;i++ {
					if (tritsHash[len(tritsHash)-1-i] != 0) {
						log.Fatalf("verify error at %d!\n", i)
					}
				}/
	}

}*/