Visual Studio 2008 Part 22

[過去ﾛｸﾞ] Visual Studio 2008 Part 22 (314ﾚｽ)
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181: デフォルトの名無しさん [sage] 2018/09/15(土) 14:05:09.61 ID:heijdb7v

Intel® 64 and IA-32 Architectures Software Developer’s Manual

[Vol 1]

11.6.8 Compatibility of SIMD and x87 FPU Floating-Point Data Types

SSE and SSE2 extensions operate on the same single-precision and double-precision floating-point data types that
the x87 FPU operates on. However, when operating on these data types, the SSE and SSE2 extensions operate on
them in their native format (single-precision or double-precision), in contrast to the x87 FPU which extends them
to double extended-precision floating-point format to perform computations and then rounds the result back to a
single-precision or double-precision format before writing results to memory. Because the x87 FPU operates on a
higher precision format and then rounds the result to a lower precision format, it may return a slightly different
result when performing the same operation on the same single-precision or double-precision floating-point values
than is returned by the SSE and SSE2 extensions. The difference occurs only in the least-significant bits of the
significand.

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191: デフォルトの名無しさん [sage] 2018/09/15(土) 20:37:06.43 ID:UR1d6CKz

ソース：
#include "stdafx.h"
#include <math.h>
using namespace System;

template<typename T> static double calc_norm_and_regulate(int num, T* r, bool regulate){ // <float> for debug.
double norm = 0;
for (int i=0;i<num;i++) norm += (double)r[i] * (double)r[i];
norm = sqrt(norm);
if (regulate) for (int i=0;i<num;i++) r[i] = (T)(r[i]/norm);
return norm;
}

int main(array<System::String ^> ^args)
{
int count = 16;
__int64 inputs_hex[16] = {
0x0000000000000000, 0x0000000000000000, 0x0000000000000000, 0x1fedb1530240aa54,
0x0000000000000000, 0x0000000000000000, 0x0000000000000000, 0x1ff0af0d95025bc3,
0x1fc9353df6af376b, 0x0000000000000000, 0x0000000000000000, 0x0000000000000000,
0x0000000000000000, 0x0000000000000000, 0x0000000000000000, 0x0000000000000000};
double* inputs = (double*)inputs_hex;
double norm = calc_norm_and_regulate(count, inputs, false);
Console::Write(String::Format("{0:F6}, 0x{1:x16}\r\n",norm, *(__int64*)&norm));
// Release build
// 0.000000, 0x1ff68ddfb62221dd from IDE
// 0.000000, 0x1ff68ddfb62221de from command prompt
return 0;
}

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192: デフォルトの名無しさん [sage] 2018/09/15(土) 20:42:48.06 ID:UR1d6CKz

オプション等(コマンドライン）：（全てデフォのままのはずだが一応）
C/C++：
　/GL /D "WIN32" /D "NDEBUG" /D "_UNICODE" /D "UNICODE" /FD /EHa /MD /Yu"stdafx.h"
/Fp"Release\test_floating_error4.pch" /Fo"Release\\" /Fd"Release\vc90.pdb"
/W3 /nologo /c /Zi /clr /TP /errorReport:prompt /FU "c:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll"
/FU "c:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll"
/FU "c:\Windows\Microsoft.NET\Framework\v2.0.50727\System.XML.dll"
リンカ：
/OUT:"MYPATH\test_floating_error4\Release\test_floating_error4.exe"
/INCREMENTAL:NO /NOLOGO /MANIFEST
/MANIFESTFILE:"Release\test_floating_error4.exe.intermediate.manifest"
/MANIFESTUAC:"level='asInvoker' uiAccess='false'" /DEBUG
/PDB:"MYPATH\test_floating_error4\Release\test_floating_error4.pdb"
/LTCG /DYNAMICBASE /FIXED:No /NXCOMPAT /MACHINE:X86 /ERRORREPORT:PROMPT

パスは$MYPATHと書き換えた。また、投稿の為に適宜改行を入れた。
このプロジェクト名は見れば分かるとおりtest_floating_error4。

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