double res;
res = ceil(363.5);
res is 1031 instead of 364 as expected.
Does anyone know the reason? And how can I use the function ceil() and get the expected result?
Unless you're calling a different ceil() function1, or printing the result in the wrong way, it should work fine:
#include <stdio.h>
#include <math.h>
int main (void) {
double res;
res = ceil (363.5);
printf ("%f\n", res);
return 0;
}
That code outputs 364.000000 as expected. I'd suggest typing it in exactly as is to see what result you get. If it's still not 364, then you have a serious problem.
1 Such as double ceil (double x) { return 1031.0; } :-)
Related
i am trying to use dgels function of lapacke:
when i use it with malloc fucntion. it doesnot give correct value.
can anybody tell me please what is the mistake when i use malloc and create a matrix?
thankyou
/* Calling DGELS using row-major order */
#include <stdio.h>
#include <lapacke.h>
#include <conio.h>
#include <malloc.h>
int main ()
{
double a[3][2] = {{1,0},{1,1},{1,2}};
double **outputArray;
int designs=3;
int i,j,d,i_mal;
lapack_int info,m,n,lda,ldb,nrhs;
double outputArray[3][1] = {{6},{0},{0}};*/
outputArray = (double**) malloc(3* sizeof(double*));
for(i_mal=0;i_mal<3;i_mal++)
{
outputArray[i_mal] = (double*) malloc(1* sizeof(double));
}
for (i=0;i<designs;i++)
{
printf("put first value");
scanf("%lf",&outputArray[i][0]);
}
m = 3;
n = 2;
nrhs = 1;
lda = 2;
ldb = 1;
info = LAPACKE_dgels(LAPACK_ROW_MAJOR,'N',m,n,nrhs,*a,lda,*outputArray,ldb);
for(i=0;i<m;i++)
{
for(j=0;j<nrhs;j++)
{
printf("%lf ",outputArray[i][j]);
}
printf("\n");
}
getch();
return (info);
}
The problem may come from outputArray not being contiguous in memory. You may use something like this instead :
outputArray = (double**) malloc(3* sizeof(double*));
outputArray[0]=(double*) malloc(3* sizeof(double));
for (i=0;i<designs;i++){
outputArray[i]=&outputArray[0][i];
}
Don't forget to free the memory !
free(outputArray[0]);
free(outputArray);
Edit : Contiguous means that you have to allocate the memory for all values at once. See http://www.fftw.org/doc/Dynamic-Arrays-in-C_002dThe-Wrong-Way.html#Dynamic-Arrays-in-C_002dThe-Wrong-Way : some packages, like fftw or lapack require this feature for optimization. As you were calling malloc three times, you created three parts and things went wrong.
If you have a single right hand side, there is no need for a 2D array (double**). outputArray[i] is a double*, that is, the start of the i-th row ( row major). The right line may be outputArray[i]=&outputArray[0][i*nrhs]; if you have many RHS.
By doing this in your code, you are building a 3 rows, one column, that is one RHS. The solution, is of size n=2. It should be outputArray[0][0] , outputArray[1][0]. I hope i am not too wrong, check this on simple cases !
Bye,
When I try to read a line from standard input and split it into words, after removing the /n character, I get a core dumped error. Could anyone explain me the reason? What is the correct way to do this?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define LINE_LEN 50
#define MAX_PARTS 50
int main ()
{
char* token;
char *str;
char* arr[MAX_PARTS];
int i,j;
printf("Write a line: \n $:");
fgets(str, LINE_LEN, stdin);
str = strncpy(str, str, strlen(str)-1);
fflush(stdin);
i=0;
token = strtok(str, " ");
while( token != NULL )
{
arr[i] = token;
printf("%s",arr[i]);
i++;
token = strtok(NULL," ");
}
return 0;
}
You are printing the NULL pointer on your last pass through the while() loop. You probably need to reverse the printf() and strtok() calls like this:
while( token != NULL )
{
arr[i] = token;
printf("%s",arr[i]); # Must come first to avoid printing a NULL on final loop
i++;
token = strtok(NULL," ");
}
You are reading into unallocated memory.
char *str;
This declares a pointer str, which is pointing nowhere. (In fact, it points to a random location, but "nowhere" stops the guys who try to second-guess undefined behaviour.)
fgets(str, LINE_LEN, stdin);
This writes to the location str is pointing at, which is nowhere (see above). This is undefined behaviour. If your program happens to survive this (instead of SEGFAULTing right there), you cannot rely on it behaving in any sane manner from this point on.
While we're at it:
fflush(stdin);
Note that the C standard does not define the behaviour of fflush() when called on input streams, i.e. while this is well-defined under Linux (which does define this behaviour), this is a non-standard, non-portable construct that could well crash on other platforms.
I have the following piece of code in appPOSWebDlg.cpp:
#include "stdafx.h"
#include "afx.h"
#include <stdlib.h>
#include <Ras.h>
...
//Attribute
char *site;
...
// Method
int readFile() {
char * aux;
int result;
result = readParameter(hFile, aux);
if (result == 0) {
memcpy(site, aux, 256);
} else {
return 1;
}
return 0;
}
But the program stops at the memcpy line and I'm not sure why. After debugging, I can confirm that the aux parameter is being assigned correctly with the value expected. Furthermore, I even used the memcpy inside the readParameter method to assign it and had no problem. So why can't I assign that value to attribute site using the same method?
Your "site" pointer is invalid. You've defined it as a pointer, but, not allocated any space for it, so, your copy command is overlaying some code. You'll need to allocated the pointer correctly by performing a "new" and a "delete" when you are done.
I get an error message saying expression must have (pointer-to-) function type. what am i doing wrong? i just started coding, i know i suck lol. I don't understand how to get the formula for the distance to work.
#include <cmath> //headerfile
#include <iomanip>
#include <iostream>
enter code here
using namespace std;
int main()
{
double d;
double t;
double g;
char choice ='y';
//output numbers to console
while (choice == 'y' || choice =='Y')
{
cout<<"Please input a value for the time"<< endl<<endl;
cin>>t;
g = 32;
d = (g)(t*t);
if (t<0)
cout<<"You cannot have a negative time"<<endl<<endl;
else
cout<<setw(8)<<fixed<<setprecision(2)<<"\n""The distance the ball has fallen is "<<d<<" feet"<<endl<<endl;
cout<<"Would you like to run this again? y for yes, any other key for no."<< endl<<endl;
cin>>choice;
cout<<endl;
}
system ("Pause");
return 0;
}
If (g)(t*t) is supposed to be a normal multiplication operation, then it should be g*t*t.
In your code, g is a double, but you are using it as if it was a pointer to a function (d = (g)(t*t);). If what you really want is to multiply t*t by g, you forgot an *:
d = (g)*(t*t);
I have the following code:
sHexPic = string_to_hex(sPic);
sHexPic.insert(sHexPic.begin() + 2,' ');
sHexPic.insert(2," ");
I would like to know how I can put this into a counted loop and add a space after every 2nd character. So far all this does is make this string "35498700" into "35 498700", which in the end I want the final result to be something like "35 49 87 00".
I assume you would have to get the length of the string and the amount of characters in it.
I am trying to achieve this in c++/cli.
Thanks.
Here's how it would be done in C++, using a string :) (I'm using C libraries cuz I'm more familiar with C)
#include <stdio.h>
#include <string>
using namespace std;
int main()
(
string X;
int i;
int y;
X = 35498700;
y= X.size();
for(i=2;i<y;i+=2)
{
X.insert(i," ");
y=x.size(); //To update size of x
i++; //To skip the inserted space
}
printf("%s",X);
return 0;
}
Have fun :)
That would "probably" work. If it didn't then please mention so :)