# vDSP_vrampmuladd2 Multiplies a single-precision, stereo input vector by a value that ramps up on successive calls, and cumulatively adds the result to the output vector. ``` void vDSP_vrampmuladd2(const float *__I0, const float *__I1, vDSP_Stride __IS, float *__Start, const float *__Step, float *__O0, float *__O1, vDSP_Stride __OS, vDSP_Length __N); ``` ## Parameters `__I0` The first input vector, multiplied by the ramp function. `__I1` The second input vector, multiplied by the ramp function. `__IS` The stride for both input vectors. `__Start` On input, the initial value of the ramp. On output, the next value in the ramp. `__Step` The increment, or decrement if negative, between each generated element. `__O0` The first output vector. `__O1` The second output vector. `__OS` The stride for both output vectors. `__N` The number of elements that the function processes. ## Discussion The functions in this group are similar to [`vDSP_vrampmul`](/documentation/Accelerate/vDSP_vrampmul), but rather than overwriting the output vector, they add the results to the existing values in the output vector. The following code describes the calculation: ```c for (i = 0; i < N; ++i) { O[i*OS] += *Start * I[i*IS]; *Start += *Step; } ``` For example, the following code fills the array `i` with sine values: ```swift let n = vDSP_Length(1024) let i: [Float] = (0 ..< n).map { return sin(Float($0) / 20) } ``` The following illustrates the values of `i`:  The following code fills the output array, o, with increasing powers of two: ```swift var o = (0 ..< n).map { return pow(Float($0), 2) * 0.0001 } ``` The following illustrates the values of `o`:  Pass `i` as the input vector, and `o` as the output vector to [`vDSP_vrampmuladd`](/documentation/Accelerate/vDSP_vrampmuladd)… ```swift let stride = vDSP_Stride(1) var start: Float = 0 var step: Float = 0.1 vDSP_vrampmuladd(i, stride, &start, &step, &o, stride, n) ``` On return, the output vector, `o`, is overwritten with a ramped-sine wave, based on its original exponential curve:  --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)