sewardj | b941be6 | 2005-01-08 18:26:47 +0000 | [diff] [blame^] | 1 | |
| 2 | /* peach (7400, altivec supported, 450MHz, gcc -O) |
| 3 | m1 = 1.20000000000000018, exp = 1.19999999999999996 |
| 4 | m2 = 1.19999999999998885, exp = 1.19999999999999996 |
| 5 | */ |
| 6 | |
| 7 | /* peach (7400, altivec supported, 450MHz, gcc) |
| 8 | m1 = 1.20000000000000018, exp = 1.19999999999999996 |
| 9 | m2 = 1.19999999999998885, exp = 1.19999999999999996 |
| 10 | */ |
| 11 | |
| 12 | /* phoenix, gcc -O |
| 13 | m1 = 1.19999999999999996, exp = 1.19999999999999996 |
| 14 | m2 = 1.19999999999999996, exp = 1.19999999999999996 |
| 15 | */ |
| 16 | |
| 17 | /* phoenix, icc -O |
| 18 | m1 = 1.19999999999999996, exp = 1.19999999999999996 |
| 19 | m2 = 1.19999999999999996, exp = 1.19999999999999996 |
| 20 | */ |
| 21 | |
| 22 | /* phoenix, gcc -O, iropt-level=2 |
| 23 | m1 = 1.20000000000000040, exp = 1.19999999999999996 |
| 24 | m2 = 1.19999999999999440, exp = 1.19999999999999996 |
| 25 | */ |
| 26 | |
| 27 | /* phoenix, gcc -O, iropt-level=1/0 |
| 28 | m1 = 1.20000000000000018, exp = 1.19999999999999996 |
| 29 | m2 = 1.19999999999998885, exp = 1.19999999999999996 |
| 30 | */ |
| 31 | |
| 32 | |
| 33 | #include <stdlib.h> |
| 34 | #include <stdio.h> |
| 35 | #include <math.h> |
| 36 | |
| 37 | #define NNN 1000 |
| 38 | |
| 39 | |
| 40 | double |
| 41 | my_mean1 (const double data[], size_t stride, const size_t size) |
| 42 | { |
| 43 | /* Compute the arithmetic mean of a dataset using the recurrence relation |
| 44 | mean_(n) = mean(n-1) + (data[n] - mean(n-1))/(n+1) */ |
| 45 | long double mean = 0; |
| 46 | size_t i; |
| 47 | |
| 48 | for (i = 0; i < size; i++) |
| 49 | { |
| 50 | mean += (data[i * stride] - mean) / (i + 1); |
| 51 | } |
| 52 | return mean; |
| 53 | } |
| 54 | |
| 55 | double |
| 56 | my_mean2 (const double data[], size_t stride, const size_t size) |
| 57 | { |
| 58 | /* Compute the arithmetic mean of a dataset using the |
| 59 | obvious scheme. */ |
| 60 | int i; |
| 61 | long double sum = 0; |
| 62 | for (i = 0; i < size; i++) |
| 63 | sum += data[i * stride]; |
| 64 | return sum / (double)size; |
| 65 | } |
| 66 | |
| 67 | |
| 68 | int main (void) |
| 69 | { |
| 70 | int i; |
| 71 | const size_t nacc2 = NNN+1; |
| 72 | double numacc2[NNN+1] ; |
| 73 | |
| 74 | numacc2[0] = 1.2 ; |
| 75 | |
| 76 | for (i = 1 ; i < NNN; i += 2) |
| 77 | numacc2[i] = 1.1 ; |
| 78 | |
| 79 | for (i = 1 ; i < NNN; i += 2) |
| 80 | numacc2[i+1] = 1.3 ; |
| 81 | |
| 82 | #if 1 |
| 83 | asm __volatile__("fninit"); |
| 84 | #endif |
| 85 | |
| 86 | { |
| 87 | double m1 = my_mean1 (numacc2, 1, nacc2); |
| 88 | double m2 = my_mean2 (numacc2, 1, nacc2); |
| 89 | double expected_mean = 1.2; |
| 90 | printf("m1 = %19.17f, exp = %19.17f\n", m1, expected_mean); |
| 91 | printf("m2 = %19.17f, exp = %19.17f\n", m2, expected_mean); |
| 92 | } |
| 93 | |
| 94 | return 0; |
| 95 | } |
| 96 | |
| 97 | |