Task 3 is done!

2025.04.18/01Ex/main.c

@@ -24,7 +24,6 @@ int main(int argc, char *argv[])
 		return 1;
 	}
 
-	// TODO: Удалить вывод в stderr
 	X = (double *)malloc(n * sizeof(double));
 	if (!X)
 	{
@@ -64,6 +63,16 @@ int main(int argc, char *argv[])
 	r = t1_solve(x_0, n, X, Y);
 	t = (clock() - t) / CLOCKS_PER_SEC;
 	
+	if (fabs(r - DBL_MAX) < DBL_EPSILON)
+	{
+		fprintf(stderr, "%s\n", ERR_FUNC);
+
+		free(X);
+		free(Y);
+
+		return 4;
+	}
+
 	printf("%s : Task = %d Result = %e Elapsed = %.2f\n", argv[0], task, r, t);
 
 	free(X);

2025.04.18/02Ex/io_status.h

@@ -4,6 +4,7 @@
 #define ERR_MEM	"Error: Not enough memory!"
 #define ERR_OPEN "Error: Cannot open file"
 #define ERR_READ "Error: Cannot read file"
+#define ERR_FUNC "Error: Algorithm is not applicable!"
 
 typedef enum _io_status
 {

2025.04.18/02Ex/main.c

@@ -1,6 +1,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
+#include <float.h>
+#include <math.h>
 
 #include "array_io.h"
 #include "io_status.h"
@@ -63,6 +65,16 @@ int main(int argc, char *argv[])
 	r = t2_solve(x_0, n, X, Y);
 	t = (clock() - t) / CLOCKS_PER_SEC;
 	
+	if (fabs(r - DBL_MAX) < DBL_EPSILON)
+	{
+		fprintf(stderr, "%s\n", ERR_FUNC);
+
+		free(X);
+		free(Y);
+
+		return 4;
+	}
+
 	printf("%s : Task = %d Result = %e Elapsed = %.2f\n", argv[0], task, r, t);
 
 	free(X);

2025.04.18/02Ex/solve.c

@@ -7,16 +7,15 @@
 // the Newton interpolation polynomial
 double t2_solve (const double x_0, const int n, const double * restrict X, double * restrict Y)
 {
-	double last_x, last_y;
-	
-	double value = 0;
-	double start_value = 0;
+	double value, start_value;
 
 	for (int k = 0; k < n-1; ++k)
 	{
+		double last_x; 
+		double last_y = Y[n-1];
+
 //		printf ("------- K = %d -------\n", k);
 		
-		last_y = Y[n-1];
 		for (int i = n-2; i >= k; --i)
 		{
 			const double x_i = X[i-k];
@@ -33,16 +32,13 @@ double t2_solve (const double x_0, const int n, const double * restrict X, doubl
 		}
 	}
 
-	last_x = X[0];
 	start_value = 1;
-	value = Y[0];
+	value = 0;
 
-	for (int i = 1; i < n; ++i)
+	for (int i = 0; i < n; ++i)
 	{
-		start_value *= (x_0 - last_x);
-		if (fabs(Y[i]) > DBL_EPSILON) 
-			value += Y[i] * start_value;
-		last_x = X[i];
+		value += Y[i] * start_value;
+		start_value *= (x_0 - X[i]);
 	}
 
 	return value;

2025.04.18/03Ex/Makefile

@@ -0,0 +1,42 @@
+WFLAGS = -fstack-protector-all -W -Wall -Wextra -Wunused \
+-Wempty-body -Wlogical-op -Wold-style-declaration -Wmissing-parameter-type \
+-Wignored-qualifiers -Winit-self -Wshadow -Wtype-limits \
+-Wpointer-arith -Wformat-security -Wmissing-format-attribute -Wformat=1 \
+-Wdeclaration-after-statement -Wbad-function-cast -Wnested-externs \
+-Wmissing-prototypes -Wmissing-declarations -Wold-style-definition \
+-Wcast-align -Werror -pedantic -pedantic-errors -Wfloat-equal \
+-Wwrite-strings -Wno-long-long -std=gnu99 -Wstrict-prototypes \
+-Wmissing-field-initializers -Wpointer-sign
+
+LDFLAGS = -std=gnu99 -mfpmath=sse -O3
+LDLIBS = -lm
+
+ifeq ($(OS),Windows_NT)
+	EXE = exe
+	CLEAN = del
+	LDLIBS += -lssp
+else
+	EXE = out
+	CLEAN = rm -f
+endif
+
+TARGET = a03.$(EXE)
+OBJ = main.o solve.o array_io.o
+
+%.o: %.c
+	gcc $(WFLAGS) $(LDFLAGS) -c $< -o $@
+
+$(TARGET): $(OBJ)
+	gcc $^ -o $@ $(LDLIBS)
+
+# Отладочная сборка (gdb)
+gdb: LDFLAGS = -std=gnu99 -mfpmath=sse -g -O0
+gdb: clean $(TARGET)
+
+# Профилировочная сборка (gprof)
+prof: LDFLAGS += -pg
+prof: LDLIBS += -pg
+prof: clean $(TARGET)
+
+clean:
+	$(CLEAN) *.o *$(EXE)

2025.04.18/03Ex/array_io.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <string.h>
+#include "array_io.h"
+
+io_status read_values (double * restrict X, double * restrict Y, const int n, const char * restrict name)
+{
+	FILE *fp;
+	if (!(fp = fopen(name, "r"))) 
+		return ERROR_OPEN;
+
+	for (int i = 0; i < n; ++i)
+		if (fscanf(fp, "%lf\t%lf", X + i, Y + i) != 2)
+		{ fclose(fp); return ERROR_READ; }
+
+	fclose(fp);
+	return SUCCESS;
+}
+
+void print_values (const double * restrict X, const double * restrict Y, const int n, const int p)
+{
+	int np = (n > p ? p : n);
+
+	for (int i = 0; i < np; i++)
+		printf("f(%lf) = %lf\n", X[i], Y[i]);
+}
+

2025.04.18/03Ex/array_io.h

@@ -0,0 +1,9 @@
+#ifndef ARRAY_IO_H
+#define ARRAY_IO_H
+
+#include "io_status.h"
+
+io_status read_values (double * restrict X, double * restrict Y, const int n, const char * restrict name);
+void print_values (const double * restrict X, const double * restrict Y, const int n, const int p);
+
+#endif

2025.04.18/03Ex/io_status.h

@@ -0,0 +1,16 @@
+#ifndef IO_STATUS_H
+#define IO_STATUS_H
+
+#define ERR_MEM	"Error: Not enough memory!"
+#define ERR_OPEN "Error: Cannot open file"
+#define ERR_READ "Error: Cannot read file"
+#define ERR_FUNC "Error: Algorithm is not applicable!"
+
+typedef enum _io_status
+{
+	SUCCESS,
+	ERROR_OPEN,
+	ERROR_READ
+} io_status;
+
+#endif

2025.04.18/03Ex/main.c

@@ -0,0 +1,85 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <float.h>
+#include <math.h>
+
+#include "array_io.h"
+#include "io_status.h"
+#include "solve.h"
+
+/* ./a.out x_0 n filename */
+int main(int argc, char *argv[])
+{
+	double x_0, t, r = 0, *X = 0, *Y = 0;
+	int n, task = 3;
+	char *name = 0;
+	io_status ret;
+
+	if (
+			!((argc == 4) && 
+			sscanf(argv[1], "%lf", &x_0) == 1 &&
+			((sscanf(argv[2], "%d", &n) == 1) && n > 0) &&
+			((name = argv[3]) && name))
+	) {
+		fprintf(stderr, "Usage: %s x_0 n filename\n", argv[0]);
+		return 1;
+	}
+
+	X = (double *)malloc(n * sizeof(double));
+	if (!X)
+	{
+		fprintf(stderr, "%s\n", ERR_MEM);
+		return 2;
+	}
+	
+	Y = (double *)malloc(n * sizeof(double));
+	if (!Y)
+	{
+		free(X);
+		fprintf(stderr, "%s\n", ERR_MEM);
+		return 2;
+	}
+
+	ret = read_values(X, Y, n, name);
+	do {
+		switch (ret)
+		{
+			case SUCCESS:
+				continue;
+			case ERROR_OPEN:	
+				fprintf(stderr, "%s '%s'!\n", ERR_OPEN, name);
+				break;
+			case ERROR_READ:
+				fprintf(stderr, "%s '%s'!\n", ERR_READ, name);
+				break;
+		}
+
+		free(X);
+		free(Y);
+
+		return 3; 
+	} while (0);
+
+	t = clock();
+	r = t3_solve(x_0, n, X, Y);
+	t = (clock() - t) / CLOCKS_PER_SEC;
+
+	if (fabs(r - DBL_MAX) < DBL_EPSILON)
+	{
+		fprintf(stderr, "%s\n", ERR_FUNC);
+
+		free(X);
+		free(Y);
+
+		return 4;
+	}
+		
+	printf("%s : Task = %d Result = %e Elapsed = %.2f\n", argv[0], task, r, t);
+
+	free(X);
+	free(Y);
+
+	return 0;
+}
+

2025.04.18/03Ex/solve.c

@@ -0,0 +1,36 @@
+#include "solve.h"
+
+#include <float.h>
+#include <math.h>
+#include <stdio.h>
+
+
+// Interpolation polynomial according to Aitken's scheme
+double t3_solve (const double x_0, const int n, const double * restrict X, double * restrict Y)
+{
+	for (int k = 0; k < n-1; ++k)
+	{
+		double x_j; 
+		double y_j = Y[n-1];
+
+//		printf ("------- K = %d -------\n", k);
+		
+		for (int i = n-2; i >= k; --i)
+		{
+			const double x_i = X[i-k];
+			const double y_i = Y[i];
+			x_j = X[i+1];
+			
+			if (fabs(x_j - x_i) < DBL_EPSILON)
+				return DBL_MAX;
+			
+			Y[i+1] = ((x_0-x_i) * y_j - (x_0-x_j) * y_i) / (x_j - x_i);
+//			printf ("I = %d, f(x%d, ... , x%d) = %lf\n", i, i-k+1, i+2, Y[i+1]);
+
+			y_j = y_i;
+		}
+	}
+
+	return Y[n-1];
+}
+

2025.04.18/03Ex/solve.h

@@ -0,0 +1,6 @@
+#ifndef SOLVE_H
+#define SOLVE_H
+
+double t3_solve (const double x_0, const int n, const double * restrict X, double * restrict Y);
+
+#endif

2025.04.18/tests/constant.txt

@@ -0,0 +1,7 @@
+0 5
+1 5
+2 5
+3 5
+4 5
+5 5
+6 6

2025.04.18/tests/err.txt

@@ -0,0 +1,4 @@
+1	1
+1	1
+2	2
+2	3

2025.04.18/tests/x_2.txt

@@ -1,6 +1,3 @@
 1	1
 2	4
 3	9
-4	16
-5	25
-6	36

2025.04.18/tests/x_3.txt

@@ -0,0 +1,7 @@
+-1	-6
+0	0
+0.42265	0.3849
+1	0
+1.57735	-0.3849
+2	0
+3	6