Update fp-contract.md to remove Itanium reference (MicrosoftDocs#189)

manbearian · Colin Robertson · commit d649345a6651 · 2018-03-12T13:40:30.000-07:00
* Update fp-contract.md

Updating content to remove Itanium reference.

* Update fp-contract.md

Lint markdown, some edits.
diff --git a/docs/preprocessor/fp-contract.md b/docs/preprocessor/fp-contract.md
@@ -1,79 +1,78 @@
 ---
 title: "fp_contract | Microsoft Docs"
 ms.custom: ""
-ms.date: "11/04/2016"
-ms.reviewer: ""
-ms.suite: ""
+ms.date: "03/12/2018"
 ms.technology: ["cpp-tools"]
-ms.tgt_pltfrm: ""
 ms.topic: "reference"
 f1_keywords: ["vc-pragma.fp_contract", "fp_contract_CPP"]
 dev_langs: ["C++"]
 helpviewer_keywords: ["pragmas, fp_contract", "fp_contract pragma"]
 ms.assetid: 15b97338-6680-4287-ba2a-2dccc5b2ccf5
-caps.latest.revision: 12
 author: "corob-msft"
 ms.author: "corob"
 manager: "ghogen"
 ms.workload: ["cplusplus"]
 ---
 # fp_contract
-Determines whether floating-point contraction will take place.  
-  
-## Syntax  
-  
-```  
-#pragma fp_contract [ON | OFF]  
-```  
-  
+
+Determines whether floating-point contraction takes place. A floating-point contraction is an instruction such as FMA (Fused-Multiply-Add) that combines two separate floating point operations into a single instruction. Use of these instructions can affect floating-point precision, because instead of rounding after each operation, the processor may round only once after both operations.
+
+## Syntax
+
+> **#pragma fp_contract** [ **on** | **off** ]  
+
 ## Remarks  
- By default, `fp_contract` is ON.  
-  
- For more information on floating-point behavior, see [/fp (Specify Floating-Point Behavior)](../build/reference/fp-specify-floating-point-behavior.md).  
-  
- Other floating-point pragmas include:  
-  
--   [fenv_access](../preprocessor/fenv-access.md)  
-  
--   [float_control](../preprocessor/float-control.md)  
-  
-## Example  
- The code generated from this sample does not use the Fused Multiply Add (**fma**) instruction on Itanium processors. If you comment out `#pragma fp_contract (off)`, the generated code will use the **fma** instruction.  
-  
-```  
-// pragma_directive_fp_contract.cpp  
-// compile with: /O2  
-#include <stdio.h>  
-#include <float.h>  
-  
-#pragma fp_contract (off)   
-  
-int main() {  
-   double z, b, t;  
-  
-   for (int i = 0; i < 10; i++) {  
-      b = i * 5.5;  
-      t = i * 56.025;  
-      _set_controlfp(_PC_24, _MCW_PC);  
-  
-      z = t * i + b;  
-      printf_s ("out=%.15e\n", z);  
-   }  
-}  
-```  
-  
-```Output  
-out=0.000000000000000e+000  
-out=6.152500152587891e+001  
-out=2.351000061035156e+002  
-out=5.207249755859375e+002  
-out=9.184000244140625e+002  
-out=1.428125000000000e+003  
-out=2.049899902343750e+003  
-out=2.783724853515625e+003  
-out=3.629600097656250e+003  
-out=4.587524902343750e+003  
-```  
+
+By default, **fp_contract** is **on**. This tells the compiler to use floating-point contraction instructions where possible. Set **fp_contract** to **off** to preserve individual floating-point instructions.
+
+For more information on floating-point behavior, see [/fp (Specify Floating-Point Behavior)](../build/reference/fp-specify-floating-point-behavior.md).
+
+Other floating-point pragmas include:
+
+- [fenv_access](../preprocessor/fenv-access.md)
+
+- [float_control](../preprocessor/float-control.md)
+
+## Example
+
+The code generated from this sample does not use a fused-multiply-add instruction even when it is available on the target processor. If you comment out `#pragma fp_contract (off)`, the generated code may use a fused-multiply-add instruction if it is available.  
   
-## See Also  
- [Pragma Directives and the __Pragma Keyword](../preprocessor/pragma-directives-and-the-pragma-keyword.md)
+```cpp
+// pragma_directive_fp_contract.cpp
+// on x86 and x64 compile with: /O2 /fp:fast /arch:AVX2
+// other platforms compile with: /O2
+
+#include <stdio.h>
+
+// remove the following line to enable FP contractions
+#pragma fp_contract (off)
+
+int main() {
+   double z, b, t;
+
+   for (int i = 0; i < 10; i++) {
+      b = i * 5.5;
+      t = i * 56.025;
+
+      z = t * i + b;
+      printf("out = %.15e\n", z);
+   }
+}
+```
+
+```Output
+out = 0.000000000000000e+00
+out = 6.152500000000000e+01
+out = 2.351000000000000e+02
+out = 5.207249999999999e+02
+out = 9.184000000000000e+02
+out = 1.428125000000000e+03
+out = 2.049900000000000e+03
+out = 2.783725000000000e+03
+out = 3.629600000000000e+03
+out = 4.587525000000000e+03
+```
+
+## See also
+
+[Pragma Directives and the __Pragma Keyword](../preprocessor/pragma-directives-and-the-pragma-keyword.md)
