Diff: src/Cortex-M4-M3/FastMathFunctions/arm_sqrt_q31.c

Revision:

0:1014af42efd9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Cortex-M4-M3/FastMathFunctions/arm_sqrt_q31.c	Thu Mar 10 15:07:50 2011 +0000
@@ -0,0 +1,124 @@
+/* ----------------------------------------------------------------------  
+* Copyright (C) 2010 ARM Limited. All rights reserved.  
+*  
+* $Date:        29. November 2010  
+* $Revision: 	V1.0.3  
+*  
+* Project: 	    CMSIS DSP Library  
+* Title:		arm_sqrt_q31.c  
+*  
+* Description:	Q31 square root function. 
+*  
+* Target Processor: Cortex-M4/Cortex-M3
+*  
+* Version 1.0.3 2010/11/29 
+*    Re-organized the CMSIS folders and updated documentation.  
+*   
+* Version 1.0.2 2010/11/11  
+*    Documentation updated.   
+*  
+* Version 1.0.1 2010/10/05   
+*    Production release and review comments incorporated.  
+*  
+* Version 1.0.0 2010/09/20   
+*    Production release and review comments incorporated.  
+* -------------------------------------------------------------------- */ 
+ 
+#include "arm_math.h" 
+#include "arm_common_tables.h" 
+ 
+/**  
+ * @ingroup groupFastMath  
+ */ 
+ 
+/**  
+ * @addtogroup SQRT  
+ * @{  
+ */ 
+ 
+/** 
+ * @brief Q31 square root function. 
+ * @param[in]   in    input value.  The range of the input value is [0 +1) or 0x00000000 to 0x7FFFFFFF. 
+ * @param[out]  *pOut square root of input value. 
+ * @return The function returns ARM_MATH_SUCCESS if input value is positive value or ARM_MATH_ARGUMENT_ERROR if 
+ * <code>in</code> is negative value and returns zero output for negative values. 
+ */ 
+ 
+arm_status arm_sqrt_q31( 
+  q31_t in, 
+  q31_t * pOut) 
+{ 
+  q63_t out; 
+  q63_t prevOut; 
+  q31_t oneByOut; 
+  uint32_t signBits; 
+ 
+ 
+  if(in > 0) 
+  { 
+ 
+    /* run for ten iterations */ 
+ 
+    /* Take initial guess as half of the input and first iteration */ 
+    out = (in >> 1) + 0x3FFFFFFF; 
+ 
+    /* Calculation of reciprocal of out */ 
+    /* oneByOut contains reciprocal of out which is in 2.30 format  
+       and oneByOut should be upscaled by signBits */ 
+    signBits = arm_recip_q31((q31_t) out, &oneByOut, (q31_t*)armRecipTableQ31); 
+ 
+    /* 0.5 * (out) */ 
+    out = out >> 1u; 
+ 
+    /* prevOut = 0.5 * out + (in * (oneByOut << signBits))) */ 
+    prevOut = out + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    /* Third iteration */ 
+    signBits = arm_recip_q31((q31_t) prevOut, &oneByOut, (q31_t*)armRecipTableQ31); 
+    prevOut = prevOut >> 1u; 
+    out = prevOut + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    signBits = arm_recip_q31((q31_t) out, &oneByOut, (q31_t*)armRecipTableQ31); 
+    out = out >> 1u; 
+    prevOut = out + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    /* Fifth iteration */ 
+    signBits = arm_recip_q31((q31_t) prevOut, &oneByOut, (q31_t*)armRecipTableQ31); 
+    prevOut = prevOut >> 1u; 
+    out = prevOut + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    signBits = arm_recip_q31((q31_t) out, &oneByOut, (q31_t*)armRecipTableQ31); 
+    out = out >> 1u; 
+    prevOut = out + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    /* Seventh iteration */ 
+    signBits = arm_recip_q31((q31_t) prevOut, &oneByOut, (q31_t*)armRecipTableQ31); 
+    prevOut = prevOut >> 1u; 
+    out = prevOut + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    signBits = arm_recip_q31((q31_t) out, &oneByOut, (q31_t*)armRecipTableQ31); 
+    out = out >> 1u; 
+    prevOut = out + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    signBits = arm_recip_q31((q31_t) prevOut, &oneByOut, (q31_t*)armRecipTableQ31); 
+    prevOut = prevOut >> 1u; 
+    out = prevOut + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    /* tenth iteration */ 
+    signBits = arm_recip_q31((q31_t) out, &oneByOut, (q31_t*)armRecipTableQ31); 
+    out = out >> 1u; 
+    *pOut = out + (((q31_t) (((q63_t) in * oneByOut) >> 32)) << signBits); 
+ 
+    return (ARM_MATH_SUCCESS); 
+  } 
+  else 
+  { 
+    *pOut = 0; 
+    return (ARM_MATH_ARGUMENT_ERROR); 
+  } 
+ 
+} 
+ 
+/**  
+ * @} end of SQRT group  
+ */