spigotcpp/Spigot.cpp
A.M. Rowsell ec2a96b0ad
Very small changes
Considering ways to take the algorithm and turn it into
OpenCL/Boost::Compute functions/code which would offer
a large speed increase.

Also, if I can figure out how to start from any arbitrary
digit (which is supposed to be possible) then multi-threading
would also give great speedups.
2023-10-08 07:29:55 -04:00

79 lines
2.5 KiB
C++

#include <iostream>
#include <cmath>
#include <cassert>
#include "Spigot.hpp"
Spigot::Spigot(int requestedNumDigits) {
/* create list for number of digits times 10 / 3 */
this->spigotListLength = (requestedNumDigits * 10) / 3;
this->spigotList.resize(this->spigotListLength, 2); // list is initialized with all 2
this->carry = 0;
return;
}
void Spigot::pump(void) {
int tempPreDigit = 0;
int j = this->spigotListLength - 1;
int i = j;
/*
* This could be handled using boost::compute
* with a BOOST_COMPUTE_FUNCTION that just
* multiplies every item by 10.
*/
while(i >= 0) {
this->spigotList[i] *= 10;
i--;
}
this->carry = 0;
i = j;
// note this does *not* handle the i=0 case
/*
* This might also be able to be sped up
* with OpenCL/boost::compute by creating
* another custom function, but because
* the carry has to be passed along this might
* not work well
*/
while(i > 0) {
this->spigotList[i] += this->carry;
this->carry = (this->spigotList[i] / (i * 2 + 1)) * i;
this->spigotList[i] = this->spigotList[i] % (i * 2 + 1);
i--;
}
// special case of i = 0
this->spigotList[0] += this->carry;
tempPreDigit = this->spigotList[0] / 10;
this->spigotList[0] -= (tempPreDigit * 10);
try {
// handle the cases depending on the tempPreDigit
if(tempPreDigit >= 0 && tempPreDigit <= 8) {
// output all predigits
long unsigned pdLen = this->preDigits.size();
for(long unsigned int j = 0; j < pdLen; j++) {
std::cout << this->preDigits.back();
this->preDigits.pop_back();
}
this->preDigits.insert(this->preDigits.begin(), tempPreDigit);
} else if(tempPreDigit == 9) {
this->preDigits.insert(this->preDigits.begin(), tempPreDigit);
} else if(tempPreDigit == 10) {
tempPreDigit = 0;
long unsigned pdLen = this->preDigits.size();
for(long unsigned int j = 0; j < pdLen; j++) {
std::cout << (this->preDigits.back() + 1) % 10;
this->preDigits.pop_back();
}
this->preDigits.insert(this->preDigits.begin(), tempPreDigit);
} else {
std::cout << "We should never have gotten here -- shit has hit the fan!" << std::endl;
}
} catch (int e) {
std::cout << "An exception " << e << " occurred." << std::endl;
}
std::cout << std::flush;
return;
}