# Compression and gathering functions Compress vectors based on the nonzero elements in a gating vector, or gather vectors based on a separate vector that contains indices. ## Topics ### Vector compression The functions in this group compress an input vector by eliminating elements that correspond to zero values in a gating vector. [`static func compress(T, gatingVector: U, nonZeroGatingCount: Int?) -> [Float]`](/documentation/Accelerate/vDSP/compress(_:gatingVector:nonZeroGatingCount:)-3c7yk) Returns a compressed copy of the specified single-precision vector using the nonzero values in a gating vector. [`static func compress(T, gatingVector: U, nonZeroGatingCount: Int?) -> [Double]`](/documentation/Accelerate/vDSP/compress(_:gatingVector:nonZeroGatingCount:)-93v23) Returns a compressed copy of the specified double-precision vector using the nonzero values in a gating vector. [`static func compress(T, gatingVector: U, result: inout V)`](/documentation/Accelerate/vDSP/compress(_:gatingVector:result:)-7fvy9) Compresses the specified single-precision vector using the nonzero values in a gating vector. [`static func compress(T, gatingVector: U, result: inout V)`](/documentation/Accelerate/vDSP/compress(_:gatingVector:result:)-2yse4) Compresses the specified double-precision vector using the nonzero values in a gating vector. [`extern void vDSP_vcmprs(const float *__A, vDSP_Stride __IA, const float *__B, vDSP_Stride __IB, float *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vcmprs) Generates a compressed copy of the specified single-precision vector using the nonzero values in a gating vector. [`extern void vDSP_vcmprsD(const double *__A, vDSP_Stride __IA, const double *__B, vDSP_Stride __IB, double *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vcmprsD) Generates a compressed copy of the specified double-precision vector using the nonzero values in a gating vector. ### Vector gathering functions The functions in this group use indices or pointers stored in a source vector to generate a new vector with elements from a second source vector or memory. [`static func gather(T, indices: U) -> [Float]`](/documentation/Accelerate/vDSP/gather(_:indices:)-4jwvh) Returns a gathered copy of the specified single-precision vector using a vector that defines the indices to keep. [`static func gather(T, indices: U) -> [Double]`](/documentation/Accelerate/vDSP/gather(_:indices:)-4yt3o) Returns a gathered copy of the specified double-precision vector using a vector that defines the indices to keep. [`static func gather(T, indices: U, result: inout V)`](/documentation/Accelerate/vDSP/gather(_:indices:result:)-7erii) Gathers the specified single-precision vector using a vector that defines the indices to keep. [`static func gather(T, indices: U, result: inout V)`](/documentation/Accelerate/vDSP/gather(_:indices:result:)-34yzg) Gathers the specified double-precision vector using a vector that defines the indices to keep. [`extern void vDSP_vindex(const float *__A, const float *__B, vDSP_Stride __IB, float *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vindex) Generates a gathered copy of the specified single-precision vector using a vector that defines the zero-based indices to keep. [`extern void vDSP_vindexD(const double *__A, const double *__B, vDSP_Stride __IB, double *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vindexD) Generates a gathered copy of the specified double-precision vector using a vector that defines the zero-based indices to keep. [`extern void vDSP_vgathr(const float *__A, const vDSP_Length *__B, vDSP_Stride __IB, float *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vgathr) Generates a gathered copy of the specified single-precision vector using a vector that defines the one-based indices to keep. [`extern void vDSP_vgathrD(const double *__A, const vDSP_Length *__B, vDSP_Stride __IB, double *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vgathrD) Generates a gathered copy of the specified double-precision vector using a vector that defines the one-based indices to keep. [`extern void vDSP_vgathra(const float * const*__A, vDSP_Stride __IA, float *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vgathra) Generates a gathered copy of the specified single-precision vector using a vector that defines the pointers to the values to keep. [`extern void vDSP_vgathraD(const double * const*__A, vDSP_Stride __IA, double *__C, vDSP_Stride __IC, vDSP_Length __N);`](/documentation/Accelerate/vDSP_vgathraD) Generates a gathered copy of the specified double-precision vector using a vector that defines the pointers to the values to keep. --- 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)