my problem is just astonishing. This is the code
#define NCHANNEL 3
#define NFRAME 100
Mat RR = Mat::zeros(NCHANNEL, NFRAME-1, CV_64FC1);
double *p_0 = RR.ptr<double>(0);
double *p_1 = RR.ptr<double>(1);
double *p_2 = RR.ptr<double>(2);
cout<< p_0[NFRAME-1] << endl << p_1[NFRAME-1] << endl << p_2[NFRAME-1] << endl;
And the output is: 0 0 -6.27744e+066 .
Where is that awful number come from? it seems I'm printing a pointer or something rough in memory. (uh, 0 is the value of all other elements, of course).
You are accessing after the last element of Mat. If you use NFRAME-1 for initialization then the last element has NFRAME-2 index.
Related
I made this little currency converter program that convert dollar to franc, but when I put an amount of, for example $2000 and more, I do not have the correct format, I have this: 1.15165e+006.
I want the entire decimal amount.
Thanks
Convert USD to Franc CFA
#include <iostream>
using namespace std;
int main()
{
const double cfa_per_usd {575.825};
cout <<"**********Welcome to the USD to Franc CFA Converter************" << endl;
double cfa {0.0};
cout <<"\nEnter value in USD: ";
double dollar {0};
cin >> dollar;
cfa = dollar * cfa_per_usd;
cout << dollar <<" Dollar(s) is equivalent to " << cfa << " Francs CFA" <<endl;
return 0;
}
I found a partial answer to my problem, I have added the library , then added "fixed" key word and the "setprecision()":
cout << dollar <<" Dollar(s) is equivalent to " << fixed << setprecision(2) << cfa << " Francs CFA" <
But I realized that I only have zeros after the decimal point: just 2 “.00”, I changed the constant to 576.212 for a dollar, so if I convert $2000 I should have 1,1512,424.54 francs, but I just have 1152424.00 francs, the .54 is not there, any idea how to fix it?
I found a partial answer to my problem, I have added the library, then add "fixed" key word and the "setprecision()":
cout << dollar <<" Dollar(s) is equivalent to " << fixed << setprecision(3) << cfa << " Francs CFA" <<endl;
But I realized that I only have zeros after the decimal point: just 2 “.00”, I changed the constant to 576.212 for a dollar, so if I convert $2000 I should have 1,1512,424.54 francs, but I just have 1152424.00 francs, the .54 is not there, any idea how to fix it?
SSE intrinsics includes _mm_shuffle_ps xmm1 xmm2 immx which allows one to pick 2 elements from xmm1 concatenated with 2 elements from xmm2. However this is for floats, (implied by the _ps , packed single). However if you cast your packed integers __m128i, then you can use _mm_shuffle_ps as well:
#include <iostream>
#include <immintrin.h>
#include <sstream>
using namespace std;
template <typename T>
std::string __m128i_toString(const __m128i var) {
std::stringstream sstr;
const T* values = (const T*) &var;
if (sizeof(T) == 1) {
for (unsigned int i = 0; i < sizeof(__m128i); i++) {
sstr << (int) values[i] << " ";
}
} else {
for (unsigned int i = 0; i < sizeof(__m128i) / sizeof(T); i++) {
sstr << values[i] << " ";
}
}
return sstr.str();
}
int main(){
cout << "Starting SSE test" << endl;
cout << "integer shuffle" << endl;
int A[] = {1, -2147483648, 3, 5};
int B[] = {4, 6, 7, 8};
__m128i pC;
__m128i* pA = (__m128i*) A;
__m128i* pB = (__m128i*) B;
*pA = (__m128i)_mm_shuffle_ps((__m128)*pA, (__m128)*pB, _MM_SHUFFLE(3, 2, 1 ,0));
pC = _mm_add_epi32(*pA,*pB);
cout << "A[0] = " << A[0] << endl;
cout << "A[1] = " << A[1] << endl;
cout << "A[2] = " << A[2] << endl;
cout << "A[3] = " << A[3] << endl;
cout << "B[0] = " << B[0] << endl;
cout << "B[1] = " << B[1] << endl;
cout << "B[2] = " << B[2] << endl;
cout << "B[3] = " << B[3] << endl;
cout << "pA = " << __m128i_toString<int>(*pA) << endl;
cout << "pC = " << __m128i_toString<int>(pC) << endl;
}
Snippet of relevant corresponding assembly (mac osx, macports gcc 4.8, -march=native on an ivybridge CPU):
vshufps $228, 16(%rsp), %xmm1, %xmm0
vpaddd 16(%rsp), %xmm0, %xmm2
vmovdqa %xmm0, 32(%rsp)
vmovaps %xmm0, (%rsp)
vmovdqa %xmm2, 16(%rsp)
call __ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
....
Thus it seemingly works fine on integers, which I expected as the registers are agnostic to types, however there must be a reason why the docs say that this instruction is only for floats. Does someone know any downsides, or implications I have missed?
There is no equivalent to _mm_shuffle_ps for integers. To achieve the same effect in this case you can do
SSE2
*pA = _mm_shuffle_epi32(_mm_unpacklo_epi32(*pA, _mm_shuffle_epi32(*pB, 0xe)),0xd8);
SSE4.1
*pA = _mm_blend_epi16(*pA, *pB, 0xf0);
or change to the floating point domain like this
*pA = _mm_castps_si128(
_mm_shuffle_ps(_mm_castsi128_ps(*pA),
_mm_castsi128_ps(*pB), _MM_SHUFFLE(3, 2, 1 ,0)));
But changing domains may incur bypass latency delays on some CPUs. Keep in mind that according to Agner
The bypass delay is important in long dependency chains where latency is a bottleneck, but
not where it is throughput rather than latency that matters.
You have to test your code and see which method above is more efficient.
Fortunately, on most Intel/AMD CPUs, there is usually no penalty for using shufps between most integer-vector instructions. Agner says:
For example, I found no delay when mixing PADDD and SHUFPS [on Sandybridge].
Nehalem does have 2 bypass-delay latency to/from SHUFPS, but even then a single SHUFPS is often still faster than multiple other instructions. Extra instructions have latency, too, as well as costing throughput.
The reverse (integer shuffles between FP math instructions) is not as safe:
In Agner Fog's microarchitecture on page 112 in Example 8.3a, he shows that using PSHUFD (_mm_shuffle_epi32) instead of SHUFPS (_mm_shuffle_ps) when in the floating point domain causes a bypass delay of four clock cycles. In Example 8.3b he uses SHUFPS to remove the delay (which works in his example).
On Nehalem there are actually five domains. Nahalem seems to be the most effected (the bypass delays did not exist before Nahalem). On Sandy Bridge the delays are less significant. This is even more true on Haswell. In fact on Haswell Agner said he found no delays between SHUFPS or PSHUFD (see page 140).
As part of a reverse engineering exercise, I'm trying to write a Z3 solver to find a username and password that satisfy the program below. This is especially tough because the z3py tutorial that everyone refers to (rise4fun) is down.
#include <iostream>
#include <string>
using namespace std;
int main() {
string name, pass;
cout << "Name: ";
cin >> name;
cout << "Pass: ";
cin >> pass;
int sum = 0;
for (size_t i = 0; i < name.size(); i++) {
char c = name[i];
if (c < 'A') {
cout << "Lose: char is less than A" << endl;
return 1;
}
if (c > 'Z') {
sum += c - 32;
} else {
sum += c;
}
}
int r1 = 0x5678 ^ sum;
int r2 = 0;
for (size_t i = 0; i < pass.size(); i++) {
char c = pass[i];
c -= 48;
r2 *= 10;
r2 += c;
}
r2 ^= 0x1234;
cout << "r1: " << r1 << endl;
cout << "r2: " << r2 << endl;
if (r1 == r2) {
cout << "Win" << endl;
} else {
cout << "Lose: r1 and r2 don't match" << endl;
}
}
I got that code from the assembly of a binary, and while it may be wrong I want to focus on writing the solver. I'm starting with the first part, just calculating r1, and this is what I have:
from z3 import *
s = Solver()
sum = Int('sum')
name = Array('name', IntSort(), IntSort())
for c in name:
s.add(c < 65)
if c > 90:
sum += c - 32
else:
sum += c
r1 = Xor(sum, 0x5678)
print s.check()
print s.model()
All I'm asserting is that there are no letters less than 'A' in the array, so I expect to get back an array of any size that has numbers greater than 65.
Obviously this is completely wrong, mainly because it infinite loops. Also, I'm not sure I'm calculating sum correctly, because I don't know if it's initialized to 0. Could someone help figure out how to get this first loop working?
EDIT: I was able to get a z3 script that is close to the C++ code shown above:
from z3 import *
s = Solver()
sum = 0
name = Array('name', BitVecSort(32), BitVecSort(32))
i = Int('i')
for i in xrange(0, 1):
s.add(name[i] >= 65)
s.add(name[i] < 127)
if name[i] > 90:
sum += name[i] - 32
else:
sum += name[i]
r1 = sum ^ 0x5678
passwd = Array('passwd', BitVecSort(32), BitVecSort(32))
r2 = 0
for i in xrange(0, 5):
s.add(passwd[i] < 127)
s.add(passwd[i] >= 48)
c = passwd[i] - 48
r2 *= 10
r2 += c
r2 ^= 0x1234
s.add(r1 == r2)
print s.check()
print s.model()
This code was able to give me a correct username and password. However, I hardcoded the lengths of one for the username and five for the password. How would I change the script so I wouldn't have to hard code the lengths? And how would I generate a different solution each time I run the program?
Arrays in Z3 do not necessarily have any bounds. In this case the index-sort is Int, which means unbounded integers (not machine integers). Consequently, for c in name will run forever because it enumerates name[0], name[1], name[2], ...
It seems that you actually have a bound in the original program (name.size()), so it would suffice to enumerate up to that limit. Otherwise you might need a quantifier, e.g., \forall x of Int sort . name[x] < 65. This comes with all the warnings about quantifiers, of course (see e.g., the Z3 Guide)
Suppose the length is to be determined. Here is what I think you could do:
length = Int('length')
x = Int('x')
s.add(ForAll(x,Implies(And(x>=0,x<length),And(passwd[x] < 127,passwd[x] >=48))))
Hi i am using opencv for the line detection in ios. This is for my final year project. I want to upload the image of ecg and then extract the line from this for that i have used the opencv and sucessfuly i have extracted the line but now i want to save the line and facing much problem in that can anyone help me or any tutorial ?
I wrote something quickly, I think it can help you:
void write_lines_to_file ( string file_name, vector<vector<Point> > lines )
{
FileStorage fs ( file_name, FileStorage::WRITE );
fs << "lines" << "[";
for ( unsigned int i = 0; i < lines.size(); i++ )
{
// I've assumed each line is a vector< Point >, in index [0] the head and index [1] the tail.
fs << "{:" << "x1" << lines[i].at ( 0 ).x << "y1" << lines[i].at ( 0 ).y << "x2" << lines[i].at ( 1 ).x << "y2" << lines[i].at ( 1 ).y << "}";
}
fs.release();
}
I didn't test it and I made my own assumptions, so please be cautious when you want to use it.
I am going though the string functions doing tests to learn them (I am a newbie programmer)
Anyway, I am currently looking at setw() but I seam to not understand it... I think I understand the basic use and the use of setfil
here is my test code
http://ideone.com/czAXH
Anyway the cplusplus website says.. "format flag adjustfield (left, right or internal)" but doesn't say how to use this?
I assume this means I can do the above code but place the "spacing" after the word instead of before it..
How do I do that?
std::cout << std::left
<< "[" << std::setw(3) << 1 << "," << std::setw(5) << -100 << "]\n";
std::cout << std::internal
<< "[" << std::setw(3) << 1 << "," << std::setw(5) << -100 << "]\n";
std::cout << std::right
<< "[" << std::setw(3) << 1 << "," << std::setw(5) << -100 << "]\n";
Outputs:
[1 ,-100 ]
[ 1,- 100]
[ 1, -100]